[linux-3.10.git] / drivers / scsi / libata-core.c

/*
 *  libata-core.c - helper library for ATA
 *
 *  Maintained by:  Jeff Garzik <jgarzik@pobox.com>
 *                  Please ALWAYS copy linux-ide@vger.kernel.org
 *                  on emails.
 *
 *  Copyright 2003-2004 Red Hat, Inc.  All rights reserved.
 *  Copyright 2003-2004 Jeff Garzik
 *
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *
 *  libata documentation is available via 'make {ps|pdf}docs',
 *  as Documentation/DocBook/libata.*
 *
 *  Hardware documentation available from http://www.t13.org/ and
 *  http://www.sata-io.org/
 *
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/suspend.h>
#include <linux/workqueue.h>
#include <scsi/scsi.h>
#include "scsi.h"
#include "scsi_priv.h"
#include <scsi/scsi_host.h>
#include <linux/libata.h>
#include <asm/io.h>
#include <asm/semaphore.h>
#include <asm/byteorder.h>

#include "libata.h"

static unsigned int ata_busy_sleep (struct ata_port *ap,
                                    unsigned long tmout_pat,
                                    unsigned long tmout);
static void ata_dev_init_params(struct ata_port *ap, struct ata_device *dev);
static void ata_set_mode(struct ata_port *ap);
static void ata_dev_set_xfermode(struct ata_port *ap, struct ata_device *dev);
static unsigned int ata_get_mode_mask(struct ata_port *ap, int shift);
static int fgb(u32 bitmap);
static int ata_choose_xfer_mode(struct ata_port *ap,
                                u8 *xfer_mode_out,
                                unsigned int *xfer_shift_out);
static int ata_qc_complete_noop(struct ata_queued_cmd *qc, u8 drv_stat);
static void __ata_qc_complete(struct ata_queued_cmd *qc);

static unsigned int ata_unique_id = 1;
static struct workqueue_struct *ata_wq;

MODULE_AUTHOR("Jeff Garzik");
MODULE_DESCRIPTION("Library module for ATA devices");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);

/**
 *      ata_tf_load - send taskfile registers to host controller
 *      @ap: Port to which output is sent
 *      @tf: ATA taskfile register set
 *
 *      Outputs ATA taskfile to standard ATA host controller.
 *
 *      LOCKING:
 *      Inherited from caller.
 */

static void ata_tf_load_pio(struct ata_port *ap, struct ata_taskfile *tf)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        unsigned int is_addr = tf->flags & ATA_TFLAG_ISADDR;

        if (tf->ctl != ap->last_ctl) {
                outb(tf->ctl, ioaddr->ctl_addr);
                ap->last_ctl = tf->ctl;
                ata_wait_idle(ap);
        }

        if (is_addr && (tf->flags & ATA_TFLAG_LBA48)) {
                outb(tf->hob_feature, ioaddr->feature_addr);
                outb(tf->hob_nsect, ioaddr->nsect_addr);
                outb(tf->hob_lbal, ioaddr->lbal_addr);
                outb(tf->hob_lbam, ioaddr->lbam_addr);
                outb(tf->hob_lbah, ioaddr->lbah_addr);
                VPRINTK("hob: feat 0x%X nsect 0x%X, lba 0x%X 0x%X 0x%X\n",
                        tf->hob_feature,
                        tf->hob_nsect,
                        tf->hob_lbal,
                        tf->hob_lbam,
                        tf->hob_lbah);
        }

        if (is_addr) {
                outb(tf->feature, ioaddr->feature_addr);
                outb(tf->nsect, ioaddr->nsect_addr);
                outb(tf->lbal, ioaddr->lbal_addr);
                outb(tf->lbam, ioaddr->lbam_addr);
                outb(tf->lbah, ioaddr->lbah_addr);
                VPRINTK("feat 0x%X nsect 0x%X lba 0x%X 0x%X 0x%X\n",
                        tf->feature,
                        tf->nsect,
                        tf->lbal,
                        tf->lbam,
                        tf->lbah);
        }

        if (tf->flags & ATA_TFLAG_DEVICE) {
                outb(tf->device, ioaddr->device_addr);
                VPRINTK("device 0x%X\n", tf->device);
        }

        ata_wait_idle(ap);
}

/**
 *      ata_tf_load_mmio - send taskfile registers to host controller
 *      @ap: Port to which output is sent
 *      @tf: ATA taskfile register set
 *
 *      Outputs ATA taskfile to standard ATA host controller using MMIO.
 *
 *      LOCKING:
 *      Inherited from caller.
 */

static void ata_tf_load_mmio(struct ata_port *ap, struct ata_taskfile *tf)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        unsigned int is_addr = tf->flags & ATA_TFLAG_ISADDR;

        if (tf->ctl != ap->last_ctl) {
                writeb(tf->ctl, (void __iomem *) ap->ioaddr.ctl_addr);
                ap->last_ctl = tf->ctl;
                ata_wait_idle(ap);
        }

        if (is_addr && (tf->flags & ATA_TFLAG_LBA48)) {
                writeb(tf->hob_feature, (void __iomem *) ioaddr->feature_addr);
                writeb(tf->hob_nsect, (void __iomem *) ioaddr->nsect_addr);
                writeb(tf->hob_lbal, (void __iomem *) ioaddr->lbal_addr);
                writeb(tf->hob_lbam, (void __iomem *) ioaddr->lbam_addr);
                writeb(tf->hob_lbah, (void __iomem *) ioaddr->lbah_addr);
                VPRINTK("hob: feat 0x%X nsect 0x%X, lba 0x%X 0x%X 0x%X\n",
                        tf->hob_feature,
                        tf->hob_nsect,
                        tf->hob_lbal,
                        tf->hob_lbam,
                        tf->hob_lbah);
        }

        if (is_addr) {
                writeb(tf->feature, (void __iomem *) ioaddr->feature_addr);
                writeb(tf->nsect, (void __iomem *) ioaddr->nsect_addr);
                writeb(tf->lbal, (void __iomem *) ioaddr->lbal_addr);
                writeb(tf->lbam, (void __iomem *) ioaddr->lbam_addr);
                writeb(tf->lbah, (void __iomem *) ioaddr->lbah_addr);
                VPRINTK("feat 0x%X nsect 0x%X lba 0x%X 0x%X 0x%X\n",
                        tf->feature,
                        tf->nsect,
                        tf->lbal,
                        tf->lbam,
                        tf->lbah);
        }

        if (tf->flags & ATA_TFLAG_DEVICE) {
                writeb(tf->device, (void __iomem *) ioaddr->device_addr);
                VPRINTK("device 0x%X\n", tf->device);
        }

        ata_wait_idle(ap);
}


/**
 *      ata_tf_load - send taskfile registers to host controller
 *      @ap: Port to which output is sent
 *      @tf: ATA taskfile register set
 *
 *      Outputs ATA taskfile to standard ATA host controller using MMIO
 *      or PIO as indicated by the ATA_FLAG_MMIO flag.
 *      Writes the control, feature, nsect, lbal, lbam, and lbah registers.
 *      Optionally (ATA_TFLAG_LBA48) writes hob_feature, hob_nsect,
 *      hob_lbal, hob_lbam, and hob_lbah.
 *
 *      This function waits for idle (!BUSY and !DRQ) after writing
 *      registers.  If the control register has a new value, this
 *      function also waits for idle after writing control and before
 *      writing the remaining registers.
 *
 *      May be used as the tf_load() entry in ata_port_operations.
 *
 *      LOCKING:
 *      Inherited from caller.
 */
void ata_tf_load(struct ata_port *ap, struct ata_taskfile *tf)
{
        if (ap->flags & ATA_FLAG_MMIO)
                ata_tf_load_mmio(ap, tf);
        else
                ata_tf_load_pio(ap, tf);
}

/**
 *      ata_exec_command_pio - issue ATA command to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues PIO write to ATA command register, with proper
 *      synchronization with interrupt handler / other threads.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_exec_command_pio(struct ata_port *ap, struct ata_taskfile *tf)
{
        DPRINTK("ata%u: cmd 0x%X\n", ap->id, tf->command);

        outb(tf->command, ap->ioaddr.command_addr);
        ata_pause(ap);
}


/**
 *      ata_exec_command_mmio - issue ATA command to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues MMIO write to ATA command register, with proper
 *      synchronization with interrupt handler / other threads.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_exec_command_mmio(struct ata_port *ap, struct ata_taskfile *tf)
{
        DPRINTK("ata%u: cmd 0x%X\n", ap->id, tf->command);

        writeb(tf->command, (void __iomem *) ap->ioaddr.command_addr);
        ata_pause(ap);
}


/**
 *      ata_exec_command - issue ATA command to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues PIO/MMIO write to ATA command register, with proper
 *      synchronization with interrupt handler / other threads.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */
void ata_exec_command(struct ata_port *ap, struct ata_taskfile *tf)
{
        if (ap->flags & ATA_FLAG_MMIO)
                ata_exec_command_mmio(ap, tf);
        else
                ata_exec_command_pio(ap, tf);
}

/**
 *      ata_exec - issue ATA command to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues PIO/MMIO write to ATA command register, with proper
 *      synchronization with interrupt handler / other threads.
 *
 *      LOCKING:
 *      Obtains host_set lock.
 */

static inline void ata_exec(struct ata_port *ap, struct ata_taskfile *tf)
{
        unsigned long flags;

        DPRINTK("ata%u: cmd 0x%X\n", ap->id, tf->command);
        spin_lock_irqsave(&ap->host_set->lock, flags);
        ap->ops->exec_command(ap, tf);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);
}

/**
 *      ata_tf_to_host - issue ATA taskfile to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues ATA taskfile register set to ATA host controller,
 *      with proper synchronization with interrupt handler and
 *      other threads.
 *
 *      LOCKING:
 *      Obtains host_set lock.
 */

static void ata_tf_to_host(struct ata_port *ap, struct ata_taskfile *tf)
{
        ap->ops->tf_load(ap, tf);

        ata_exec(ap, tf);
}

/**
 *      ata_tf_to_host_nolock - issue ATA taskfile to host controller
 *      @ap: port to which command is being issued
 *      @tf: ATA taskfile register set
 *
 *      Issues ATA taskfile register set to ATA host controller,
 *      with proper synchronization with interrupt handler and
 *      other threads.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_tf_to_host_nolock(struct ata_port *ap, struct ata_taskfile *tf)
{
        ap->ops->tf_load(ap, tf);
        ap->ops->exec_command(ap, tf);
}

/**
 *      ata_tf_read_pio - input device's ATA taskfile shadow registers
 *      @ap: Port from which input is read
 *      @tf: ATA taskfile register set for storing input
 *
 *      Reads ATA taskfile registers for currently-selected device
 *      into @tf.
 *
 *      LOCKING:
 *      Inherited from caller.
 */

static void ata_tf_read_pio(struct ata_port *ap, struct ata_taskfile *tf)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;

        tf->nsect = inb(ioaddr->nsect_addr);
        tf->lbal = inb(ioaddr->lbal_addr);
        tf->lbam = inb(ioaddr->lbam_addr);
        tf->lbah = inb(ioaddr->lbah_addr);
        tf->device = inb(ioaddr->device_addr);

        if (tf->flags & ATA_TFLAG_LBA48) {
                outb(tf->ctl | ATA_HOB, ioaddr->ctl_addr);
                tf->hob_feature = inb(ioaddr->error_addr);
                tf->hob_nsect = inb(ioaddr->nsect_addr);
                tf->hob_lbal = inb(ioaddr->lbal_addr);
                tf->hob_lbam = inb(ioaddr->lbam_addr);
                tf->hob_lbah = inb(ioaddr->lbah_addr);
        }
}

/**
 *      ata_tf_read_mmio - input device's ATA taskfile shadow registers
 *      @ap: Port from which input is read
 *      @tf: ATA taskfile register set for storing input
 *
 *      Reads ATA taskfile registers for currently-selected device
 *      into @tf via MMIO.
 *
 *      LOCKING:
 *      Inherited from caller.
 */

static void ata_tf_read_mmio(struct ata_port *ap, struct ata_taskfile *tf)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;

        tf->nsect = readb((void __iomem *)ioaddr->nsect_addr);
        tf->lbal = readb((void __iomem *)ioaddr->lbal_addr);
        tf->lbam = readb((void __iomem *)ioaddr->lbam_addr);
        tf->lbah = readb((void __iomem *)ioaddr->lbah_addr);
        tf->device = readb((void __iomem *)ioaddr->device_addr);

        if (tf->flags & ATA_TFLAG_LBA48) {
                writeb(tf->ctl | ATA_HOB, (void __iomem *) ap->ioaddr.ctl_addr);
                tf->hob_feature = readb((void __iomem *)ioaddr->error_addr);
                tf->hob_nsect = readb((void __iomem *)ioaddr->nsect_addr);
                tf->hob_lbal = readb((void __iomem *)ioaddr->lbal_addr);
                tf->hob_lbam = readb((void __iomem *)ioaddr->lbam_addr);
                tf->hob_lbah = readb((void __iomem *)ioaddr->lbah_addr);
        }
}


/**
 *      ata_tf_read - input device's ATA taskfile shadow registers
 *      @ap: Port from which input is read
 *      @tf: ATA taskfile register set for storing input
 *
 *      Reads ATA taskfile registers for currently-selected device
 *      into @tf.
 *
 *      Reads nsect, lbal, lbam, lbah, and device.  If ATA_TFLAG_LBA48
 *      is set, also reads the hob registers.
 *
 *      May be used as the tf_read() entry in ata_port_operations.
 *
 *      LOCKING:
 *      Inherited from caller.
 */
void ata_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
{
        if (ap->flags & ATA_FLAG_MMIO)
                ata_tf_read_mmio(ap, tf);
        else
                ata_tf_read_pio(ap, tf);
}

/**
 *      ata_check_status_pio - Read device status reg & clear interrupt
 *      @ap: port where the device is
 *
 *      Reads ATA taskfile status register for currently-selected device
 *      and return its value. This also clears pending interrupts
 *      from this device
 *
 *      LOCKING:
 *      Inherited from caller.
 */
static u8 ata_check_status_pio(struct ata_port *ap)
{
        return inb(ap->ioaddr.status_addr);
}

/**
 *      ata_check_status_mmio - Read device status reg & clear interrupt
 *      @ap: port where the device is
 *
 *      Reads ATA taskfile status register for currently-selected device
 *      via MMIO and return its value. This also clears pending interrupts
 *      from this device
 *
 *      LOCKING:
 *      Inherited from caller.
 */
static u8 ata_check_status_mmio(struct ata_port *ap)
{
        return readb((void __iomem *) ap->ioaddr.status_addr);
}


/**
 *      ata_check_status - Read device status reg & clear interrupt
 *      @ap: port where the device is
 *
 *      Reads ATA taskfile status register for currently-selected device
 *      and return its value. This also clears pending interrupts
 *      from this device
 *
 *      May be used as the check_status() entry in ata_port_operations.
 *
 *      LOCKING:
 *      Inherited from caller.
 */
u8 ata_check_status(struct ata_port *ap)
{
        if (ap->flags & ATA_FLAG_MMIO)
                return ata_check_status_mmio(ap);
        return ata_check_status_pio(ap);
}


/**
 *      ata_altstatus - Read device alternate status reg
 *      @ap: port where the device is
 *
 *      Reads ATA taskfile alternate status register for
 *      currently-selected device and return its value.
 *
 *      Note: may NOT be used as the check_altstatus() entry in
 *      ata_port_operations.
 *
 *      LOCKING:
 *      Inherited from caller.
 */
u8 ata_altstatus(struct ata_port *ap)
{
        if (ap->ops->check_altstatus)
                return ap->ops->check_altstatus(ap);

        if (ap->flags & ATA_FLAG_MMIO)
                return readb((void __iomem *)ap->ioaddr.altstatus_addr);
        return inb(ap->ioaddr.altstatus_addr);
}


/**
 *      ata_chk_err - Read device error reg
 *      @ap: port where the device is
 *
 *      Reads ATA taskfile error register for
 *      currently-selected device and return its value.
 *
 *      Note: may NOT be used as the check_err() entry in
 *      ata_port_operations.
 *
 *      LOCKING:
 *      Inherited from caller.
 */
u8 ata_chk_err(struct ata_port *ap)
{
        if (ap->ops->check_err)
                return ap->ops->check_err(ap);

        if (ap->flags & ATA_FLAG_MMIO) {
                return readb((void __iomem *) ap->ioaddr.error_addr);
        }
        return inb(ap->ioaddr.error_addr);
}

/**
 *      ata_tf_to_fis - Convert ATA taskfile to SATA FIS structure
 *      @tf: Taskfile to convert
 *      @fis: Buffer into which data will output
 *      @pmp: Port multiplier port
 *
 *      Converts a standard ATA taskfile to a Serial ATA
 *      FIS structure (Register - Host to Device).
 *
 *      LOCKING:
 *      Inherited from caller.
 */

void ata_tf_to_fis(struct ata_taskfile *tf, u8 *fis, u8 pmp)
{
        fis[0] = 0x27;  /* Register - Host to Device FIS */
        fis[1] = (pmp & 0xf) | (1 << 7); /* Port multiplier number,
                                            bit 7 indicates Command FIS */
        fis[2] = tf->command;
        fis[3] = tf->feature;

        fis[4] = tf->lbal;
        fis[5] = tf->lbam;
        fis[6] = tf->lbah;
        fis[7] = tf->device;

        fis[8] = tf->hob_lbal;
        fis[9] = tf->hob_lbam;
        fis[10] = tf->hob_lbah;
        fis[11] = tf->hob_feature;

        fis[12] = tf->nsect;
        fis[13] = tf->hob_nsect;
        fis[14] = 0;
        fis[15] = tf->ctl;

        fis[16] = 0;
        fis[17] = 0;
        fis[18] = 0;
        fis[19] = 0;
}

/**
 *      ata_tf_from_fis - Convert SATA FIS to ATA taskfile
 *      @fis: Buffer from which data will be input
 *      @tf: Taskfile to output
 *
 *      Converts a standard ATA taskfile to a Serial ATA
 *      FIS structure (Register - Host to Device).
 *
 *      LOCKING:
 *      Inherited from caller.
 */

void ata_tf_from_fis(u8 *fis, struct ata_taskfile *tf)
{
        tf->command     = fis[2];       /* status */
        tf->feature     = fis[3];       /* error */

        tf->lbal        = fis[4];
        tf->lbam        = fis[5];
        tf->lbah        = fis[6];
        tf->device      = fis[7];

        tf->hob_lbal    = fis[8];
        tf->hob_lbam    = fis[9];
        tf->hob_lbah    = fis[10];

        tf->nsect       = fis[12];
        tf->hob_nsect   = fis[13];
}

/**
 *      ata_prot_to_cmd - determine which read/write opcodes to use
 *      @protocol: ATA_PROT_xxx taskfile protocol
 *      @lba48: true is lba48 is present
 *
 *      Given necessary input, determine which read/write commands
 *      to use to transfer data.
 *
 *      LOCKING:
 *      None.
 */
static int ata_prot_to_cmd(int protocol, int lba48)
{
        int rcmd = 0, wcmd = 0;

        switch (protocol) {
        case ATA_PROT_PIO:
                if (lba48) {
                        rcmd = ATA_CMD_PIO_READ_EXT;
                        wcmd = ATA_CMD_PIO_WRITE_EXT;
                } else {
                        rcmd = ATA_CMD_PIO_READ;
                        wcmd = ATA_CMD_PIO_WRITE;
                }
                break;

        case ATA_PROT_DMA:
                if (lba48) {
                        rcmd = ATA_CMD_READ_EXT;
                        wcmd = ATA_CMD_WRITE_EXT;
                } else {
                        rcmd = ATA_CMD_READ;
                        wcmd = ATA_CMD_WRITE;
                }
                break;

        default:
                return -1;
        }

        return rcmd | (wcmd << 8);
}

/**
 *      ata_dev_set_protocol - set taskfile protocol and r/w commands
 *      @dev: device to examine and configure
 *
 *      Examine the device configuration, after we have
 *      read the identify-device page and configured the
 *      data transfer mode.  Set internal state related to
 *      the ATA taskfile protocol (pio, pio mult, dma, etc.)
 *      and calculate the proper read/write commands to use.
 *
 *      LOCKING:
 *      caller.
 */
static void ata_dev_set_protocol(struct ata_device *dev)
{
        int pio = (dev->flags & ATA_DFLAG_PIO);
        int lba48 = (dev->flags & ATA_DFLAG_LBA48);
        int proto, cmd;

        if (pio)
                proto = dev->xfer_protocol = ATA_PROT_PIO;
        else
                proto = dev->xfer_protocol = ATA_PROT_DMA;

        cmd = ata_prot_to_cmd(proto, lba48);
        if (cmd < 0)
                BUG();

        dev->read_cmd = cmd & 0xff;
        dev->write_cmd = (cmd >> 8) & 0xff;
}

static const char * xfer_mode_str[] = {
        "UDMA/16",
        "UDMA/25",
        "UDMA/33",
        "UDMA/44",
        "UDMA/66",
        "UDMA/100",
        "UDMA/133",
        "UDMA7",
        "MWDMA0",
        "MWDMA1",
        "MWDMA2",
        "PIO0",
        "PIO1",
        "PIO2",
        "PIO3",
        "PIO4",
};

/**
 *      ata_udma_string - convert UDMA bit offset to string
 *      @mask: mask of bits supported; only highest bit counts.
 *
 *      Determine string which represents the highest speed
 *      (highest bit in @udma_mask).
 *
 *      LOCKING:
 *      None.
 *
 *      RETURNS:
 *      Constant C string representing highest speed listed in
 *      @udma_mask, or the constant C string "<n/a>".
 */

static const char *ata_mode_string(unsigned int mask)
{
        int i;

        for (i = 7; i >= 0; i--)
                if (mask & (1 << i))
                        goto out;
        for (i = ATA_SHIFT_MWDMA + 2; i >= ATA_SHIFT_MWDMA; i--)
                if (mask & (1 << i))
                        goto out;
        for (i = ATA_SHIFT_PIO + 4; i >= ATA_SHIFT_PIO; i--)
                if (mask & (1 << i))
                        goto out;

        return "<n/a>";

out:
        return xfer_mode_str[i];
}

/**
 *      ata_pio_devchk - PATA device presence detection
 *      @ap: ATA channel to examine
 *      @device: Device to examine (starting at zero)
 *
 *      This technique was originally described in
 *      Hale Landis's ATADRVR (www.ata-atapi.com), and
 *      later found its way into the ATA/ATAPI spec.
 *
 *      Write a pattern to the ATA shadow registers,
 *      and if a device is present, it will respond by
 *      correctly storing and echoing back the
 *      ATA shadow register contents.
 *
 *      LOCKING:
 *      caller.
 */

static unsigned int ata_pio_devchk(struct ata_port *ap,
                                   unsigned int device)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        u8 nsect, lbal;

        ap->ops->dev_select(ap, device);

        outb(0x55, ioaddr->nsect_addr);
        outb(0xaa, ioaddr->lbal_addr);

        outb(0xaa, ioaddr->nsect_addr);
        outb(0x55, ioaddr->lbal_addr);

        outb(0x55, ioaddr->nsect_addr);
        outb(0xaa, ioaddr->lbal_addr);

        nsect = inb(ioaddr->nsect_addr);
        lbal = inb(ioaddr->lbal_addr);

        if ((nsect == 0x55) && (lbal == 0xaa))
                return 1;       /* we found a device */

        return 0;               /* nothing found */
}

/**
 *      ata_mmio_devchk - PATA device presence detection
 *      @ap: ATA channel to examine
 *      @device: Device to examine (starting at zero)
 *
 *      This technique was originally described in
 *      Hale Landis's ATADRVR (www.ata-atapi.com), and
 *      later found its way into the ATA/ATAPI spec.
 *
 *      Write a pattern to the ATA shadow registers,
 *      and if a device is present, it will respond by
 *      correctly storing and echoing back the
 *      ATA shadow register contents.
 *
 *      LOCKING:
 *      caller.
 */

static unsigned int ata_mmio_devchk(struct ata_port *ap,
                                    unsigned int device)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        u8 nsect, lbal;

        ap->ops->dev_select(ap, device);

        writeb(0x55, (void __iomem *) ioaddr->nsect_addr);
        writeb(0xaa, (void __iomem *) ioaddr->lbal_addr);

        writeb(0xaa, (void __iomem *) ioaddr->nsect_addr);
        writeb(0x55, (void __iomem *) ioaddr->lbal_addr);

        writeb(0x55, (void __iomem *) ioaddr->nsect_addr);
        writeb(0xaa, (void __iomem *) ioaddr->lbal_addr);

        nsect = readb((void __iomem *) ioaddr->nsect_addr);
        lbal = readb((void __iomem *) ioaddr->lbal_addr);

        if ((nsect == 0x55) && (lbal == 0xaa))
                return 1;       /* we found a device */

        return 0;               /* nothing found */
}

/**
 *      ata_devchk - PATA device presence detection
 *      @ap: ATA channel to examine
 *      @device: Device to examine (starting at zero)
 *
 *      Dispatch ATA device presence detection, depending
 *      on whether we are using PIO or MMIO to talk to the
 *      ATA shadow registers.
 *
 *      LOCKING:
 *      caller.
 */

static unsigned int ata_devchk(struct ata_port *ap,
                                    unsigned int device)
{
        if (ap->flags & ATA_FLAG_MMIO)
                return ata_mmio_devchk(ap, device);
        return ata_pio_devchk(ap, device);
}

/**
 *      ata_dev_classify - determine device type based on ATA-spec signature
 *      @tf: ATA taskfile register set for device to be identified
 *
 *      Determine from taskfile register contents whether a device is
 *      ATA or ATAPI, as per "Signature and persistence" section
 *      of ATA/PI spec (volume 1, sect 5.14).
 *
 *      LOCKING:
 *      None.
 *
 *      RETURNS:
 *      Device type, %ATA_DEV_ATA, %ATA_DEV_ATAPI, or %ATA_DEV_UNKNOWN
 *      the event of failure.
 */

unsigned int ata_dev_classify(struct ata_taskfile *tf)
{
        /* Apple's open source Darwin code hints that some devices only
         * put a proper signature into the LBA mid/high registers,
         * So, we only check those.  It's sufficient for uniqueness.
         */

        if (((tf->lbam == 0) && (tf->lbah == 0)) ||
            ((tf->lbam == 0x3c) && (tf->lbah == 0xc3))) {
                DPRINTK("found ATA device by sig\n");
                return ATA_DEV_ATA;
        }

        if (((tf->lbam == 0x14) && (tf->lbah == 0xeb)) ||
            ((tf->lbam == 0x69) && (tf->lbah == 0x96))) {
                DPRINTK("found ATAPI device by sig\n");
                return ATA_DEV_ATAPI;
        }

        DPRINTK("unknown device\n");
        return ATA_DEV_UNKNOWN;
}

/**
 *      ata_dev_try_classify - Parse returned ATA device signature
 *      @ap: ATA channel to examine
 *      @device: Device to examine (starting at zero)
 *
 *      After an event -- SRST, E.D.D., or SATA COMRESET -- occurs,
 *      an ATA/ATAPI-defined set of values is placed in the ATA
 *      shadow registers, indicating the results of device detection
 *      and diagnostics.
 *
 *      Select the ATA device, and read the values from the ATA shadow
 *      registers.  Then parse according to the Error register value,
 *      and the spec-defined values examined by ata_dev_classify().
 *
 *      LOCKING:
 *      caller.
 */

static u8 ata_dev_try_classify(struct ata_port *ap, unsigned int device)
{
        struct ata_device *dev = &ap->device[device];
        struct ata_taskfile tf;
        unsigned int class;
        u8 err;

        ap->ops->dev_select(ap, device);

        memset(&tf, 0, sizeof(tf));

        err = ata_chk_err(ap);
        ap->ops->tf_read(ap, &tf);

        dev->class = ATA_DEV_NONE;

        /* see if device passed diags */
        if (err == 1)
                /* do nothing */ ;
        else if ((device == 0) && (err == 0x81))
                /* do nothing */ ;
        else
                return err;

        /* determine if device if ATA or ATAPI */
        class = ata_dev_classify(&tf);
        if (class == ATA_DEV_UNKNOWN)
                return err;
        if ((class == ATA_DEV_ATA) && (ata_chk_status(ap) == 0))
                return err;

        dev->class = class;

        return err;
}

/**
 *      ata_dev_id_string - Convert IDENTIFY DEVICE page into string
 *      @id: IDENTIFY DEVICE results we will examine
 *      @s: string into which data is output
 *      @ofs: offset into identify device page
 *      @len: length of string to return. must be an even number.
 *
 *      The strings in the IDENTIFY DEVICE page are broken up into
 *      16-bit chunks.  Run through the string, and output each
 *      8-bit chunk linearly, regardless of platform.
 *
 *      LOCKING:
 *      caller.
 */

void ata_dev_id_string(u16 *id, unsigned char *s,
                       unsigned int ofs, unsigned int len)
{
        unsigned int c;

        while (len > 0) {
                c = id[ofs] >> 8;
                *s = c;
                s++;

                c = id[ofs] & 0xff;
                *s = c;
                s++;

                ofs++;
                len -= 2;
        }
}


/**
 *      ata_noop_dev_select - Select device 0/1 on ATA bus
 *      @ap: ATA channel to manipulate
 *      @device: ATA device (numbered from zero) to select
 *
 *      This function performs no actual function.
 *
 *      May be used as the dev_select() entry in ata_port_operations.
 *
 *      LOCKING:
 *      caller.
 */
void ata_noop_dev_select (struct ata_port *ap, unsigned int device)
{
}


/**
 *      ata_std_dev_select - Select device 0/1 on ATA bus
 *      @ap: ATA channel to manipulate
 *      @device: ATA device (numbered from zero) to select
 *
 *      Use the method defined in the ATA specification to
 *      make either device 0, or device 1, active on the
 *      ATA channel.  Works with both PIO and MMIO.
 *
 *      May be used as the dev_select() entry in ata_port_operations.
 *
 *      LOCKING:
 *      caller.
 */

void ata_std_dev_select (struct ata_port *ap, unsigned int device)
{
        u8 tmp;

        if (device == 0)
                tmp = ATA_DEVICE_OBS;
        else
                tmp = ATA_DEVICE_OBS | ATA_DEV1;

        if (ap->flags & ATA_FLAG_MMIO) {
                writeb(tmp, (void __iomem *) ap->ioaddr.device_addr);
        } else {
                outb(tmp, ap->ioaddr.device_addr);
        }
        ata_pause(ap);          /* needed; also flushes, for mmio */
}

/**
 *      ata_dev_select - Select device 0/1 on ATA bus
 *      @ap: ATA channel to manipulate
 *      @device: ATA device (numbered from zero) to select
 *      @wait: non-zero to wait for Status register BSY bit to clear
 *      @can_sleep: non-zero if context allows sleeping
 *
 *      Use the method defined in the ATA specification to
 *      make either device 0, or device 1, active on the
 *      ATA channel.
 *
 *      This is a high-level version of ata_std_dev_select(),
 *      which additionally provides the services of inserting
 *      the proper pauses and status polling, where needed.
 *
 *      LOCKING:
 *      caller.
 */

void ata_dev_select(struct ata_port *ap, unsigned int device,
                           unsigned int wait, unsigned int can_sleep)
{
        VPRINTK("ENTER, ata%u: device %u, wait %u\n",
                ap->id, device, wait);

        if (wait)
                ata_wait_idle(ap);

        ap->ops->dev_select(ap, device);

        if (wait) {
                if (can_sleep && ap->device[device].class == ATA_DEV_ATAPI)
                        msleep(150);
                ata_wait_idle(ap);
        }
}

/**
 *      ata_dump_id - IDENTIFY DEVICE info debugging output
 *      @dev: Device whose IDENTIFY DEVICE page we will dump
 *
 *      Dump selected 16-bit words from a detected device's
 *      IDENTIFY PAGE page.
 *
 *      LOCKING:
 *      caller.
 */

static inline void ata_dump_id(struct ata_device *dev)
{
        DPRINTK("49==0x%04x  "
                "53==0x%04x  "
                "63==0x%04x  "
                "64==0x%04x  "
                "75==0x%04x  \n",
                dev->id[49],
                dev->id[53],
                dev->id[63],
                dev->id[64],
                dev->id[75]);
        DPRINTK("80==0x%04x  "
                "81==0x%04x  "
                "82==0x%04x  "
                "83==0x%04x  "
                "84==0x%04x  \n",
                dev->id[80],
                dev->id[81],
                dev->id[82],
                dev->id[83],
                dev->id[84]);
        DPRINTK("88==0x%04x  "
                "93==0x%04x\n",
                dev->id[88],
                dev->id[93]);
}

/**
 *      ata_dev_identify - obtain IDENTIFY x DEVICE page
 *      @ap: port on which device we wish to probe resides
 *      @device: device bus address, starting at zero
 *
 *      Following bus reset, we issue the IDENTIFY [PACKET] DEVICE
 *      command, and read back the 512-byte device information page.
 *      The device information page is fed to us via the standard
 *      PIO-IN protocol, but we hand-code it here. (TODO: investigate
 *      using standard PIO-IN paths)
 *
 *      After reading the device information page, we use several
 *      bits of information from it to initialize data structures
 *      that will be used during the lifetime of the ata_device.
 *      Other data from the info page is used to disqualify certain
 *      older ATA devices we do not wish to support.
 *
 *      LOCKING:
 *      Inherited from caller.  Some functions called by this function
 *      obtain the host_set lock.
 */

static void ata_dev_identify(struct ata_port *ap, unsigned int device)
{
        struct ata_device *dev = &ap->device[device];
        unsigned int major_version;
        u16 tmp;
        unsigned long xfer_modes;
        u8 status;
        unsigned int using_edd;
        DECLARE_COMPLETION(wait);
        struct ata_queued_cmd *qc;
        unsigned long flags;
        int rc;

        if (!ata_dev_present(dev)) {
                DPRINTK("ENTER/EXIT (host %u, dev %u) -- nodev\n",
                        ap->id, device);
                return;
        }

        if (ap->flags & (ATA_FLAG_SRST | ATA_FLAG_SATA_RESET))
                using_edd = 0;
        else
                using_edd = 1;

        DPRINTK("ENTER, host %u, dev %u\n", ap->id, device);

        assert (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ATAPI ||
                dev->class == ATA_DEV_NONE);

        ata_dev_select(ap, device, 1, 1); /* select device 0/1 */

        qc = ata_qc_new_init(ap, dev);
        BUG_ON(qc == NULL);

        ata_sg_init_one(qc, dev->id, sizeof(dev->id));
        qc->dma_dir = DMA_FROM_DEVICE;
        qc->tf.protocol = ATA_PROT_PIO;
        qc->nsect = 1;

retry:
        if (dev->class == ATA_DEV_ATA) {
                qc->tf.command = ATA_CMD_ID_ATA;
                DPRINTK("do ATA identify\n");
        } else {
                qc->tf.command = ATA_CMD_ID_ATAPI;
                DPRINTK("do ATAPI identify\n");
        }

        qc->waiting = &wait;
        qc->complete_fn = ata_qc_complete_noop;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        rc = ata_qc_issue(qc);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        if (rc)
                goto err_out;
        else
                wait_for_completion(&wait);

        status = ata_chk_status(ap);
        if (status & ATA_ERR) {
                /*
                 * arg!  EDD works for all test cases, but seems to return
                 * the ATA signature for some ATAPI devices.  Until the
                 * reason for this is found and fixed, we fix up the mess
                 * here.  If IDENTIFY DEVICE returns command aborted
                 * (as ATAPI devices do), then we issue an
                 * IDENTIFY PACKET DEVICE.
                 *
                 * ATA software reset (SRST, the default) does not appear
                 * to have this problem.
                 */
                if ((using_edd) && (qc->tf.command == ATA_CMD_ID_ATA)) {
                        u8 err = ata_chk_err(ap);
                        if (err & ATA_ABORTED) {
                                dev->class = ATA_DEV_ATAPI;
                                qc->cursg = 0;
                                qc->cursg_ofs = 0;
                                qc->cursect = 0;
                                qc->nsect = 1;
                                goto retry;
                        }
                }
                goto err_out;
        }

        swap_buf_le16(dev->id, ATA_ID_WORDS);

        /* print device capabilities */
        printk(KERN_DEBUG "ata%u: dev %u cfg "
               "49:%04x 82:%04x 83:%04x 84:%04x 85:%04x 86:%04x 87:%04x 88:%04x\n",
               ap->id, device, dev->id[49],
               dev->id[82], dev->id[83], dev->id[84],
               dev->id[85], dev->id[86], dev->id[87],
               dev->id[88]);

        /*
         * common ATA, ATAPI feature tests
         */

        /* we require DMA support (bits 8 of word 49) */
        if (!ata_id_has_dma(dev->id)) {
                printk(KERN_DEBUG "ata%u: no dma\n", ap->id);
                goto err_out_nosup;
        }

        /* quick-n-dirty find max transfer mode; for printk only */
        xfer_modes = dev->id[ATA_ID_UDMA_MODES];
        if (!xfer_modes)
                xfer_modes = (dev->id[ATA_ID_MWDMA_MODES]) << ATA_SHIFT_MWDMA;
        if (!xfer_modes) {
                xfer_modes = (dev->id[ATA_ID_PIO_MODES]) << (ATA_SHIFT_PIO + 3);
                xfer_modes |= (0x7 << ATA_SHIFT_PIO);
        }

        ata_dump_id(dev);

        /* ATA-specific feature tests */
        if (dev->class == ATA_DEV_ATA) {
                if (!ata_id_is_ata(dev->id))    /* sanity check */
                        goto err_out_nosup;

                /* get major version */
                tmp = dev->id[ATA_ID_MAJOR_VER];
                for (major_version = 14; major_version >= 1; major_version--)
                        if (tmp & (1 << major_version))
                                break;

                /*
                 * The exact sequence expected by certain pre-ATA4 drives is:
                 * SRST RESET
                 * IDENTIFY
                 * INITIALIZE DEVICE PARAMETERS
                 * anything else..
                 * Some drives were very specific about that exact sequence.
                 */
                if (major_version < 4 || (!ata_id_has_lba(dev->id)))
                        ata_dev_init_params(ap, dev);

                if (ata_id_has_lba(dev->id)) {
                        dev->flags |= ATA_DFLAG_LBA;

                        if (ata_id_has_lba48(dev->id)) {
                                dev->flags |= ATA_DFLAG_LBA48;
                                dev->n_sectors = ata_id_u64(dev->id, 100);
                        } else {
                                dev->n_sectors = ata_id_u32(dev->id, 60);
                        }

                        /* print device info to dmesg */
                        printk(KERN_INFO "ata%u: dev %u ATA-%d, max %s, %Lu sectors:%s\n",
                               ap->id, device,
                               major_version,
                               ata_mode_string(xfer_modes),
                               (unsigned long long)dev->n_sectors,
                               dev->flags & ATA_DFLAG_LBA48 ? " LBA48" : " LBA");
                } else { 
                        /* CHS */

                        /* Default translation */
                        dev->cylinders  = dev->id[1];
                        dev->heads      = dev->id[3];
                        dev->sectors    = dev->id[6];
                        dev->n_sectors  = dev->cylinders * dev->heads * dev->sectors;

                        if (ata_id_current_chs_valid(dev->id)) {
                                /* Current CHS translation is valid. */
                                dev->cylinders = dev->id[54];
                                dev->heads     = dev->id[55];
                                dev->sectors   = dev->id[56];
                                
                                dev->n_sectors = ata_id_u32(dev->id, 57);
                        }

                        /* print device info to dmesg */
                        printk(KERN_INFO "ata%u: dev %u ATA-%d, max %s, %Lu sectors: CHS %d/%d/%d\n",
                               ap->id, device,
                               major_version,
                               ata_mode_string(xfer_modes),
                               (unsigned long long)dev->n_sectors,
                               (int)dev->cylinders, (int)dev->heads, (int)dev->sectors);

                }

                ap->host->max_cmd_len = 16;
        }

        /* ATAPI-specific feature tests */
        else {
                if (ata_id_is_ata(dev->id))             /* sanity check */
                        goto err_out_nosup;

                rc = atapi_cdb_len(dev->id);
                if ((rc < 12) || (rc > ATAPI_CDB_LEN)) {
                        printk(KERN_WARNING "ata%u: unsupported CDB len\n", ap->id);
                        goto err_out_nosup;
                }
                ap->cdb_len = (unsigned int) rc;
                ap->host->max_cmd_len = (unsigned char) ap->cdb_len;

                /* print device info to dmesg */
                printk(KERN_INFO "ata%u: dev %u ATAPI, max %s\n",
                       ap->id, device,
                       ata_mode_string(xfer_modes));
        }

        DPRINTK("EXIT, drv_stat = 0x%x\n", ata_chk_status(ap));
        return;

err_out_nosup:
        printk(KERN_WARNING "ata%u: dev %u not supported, ignoring\n",
               ap->id, device);
err_out:
        dev->class++;   /* converts ATA_DEV_xxx into ATA_DEV_xxx_UNSUP */
        DPRINTK("EXIT, err\n");
}


static inline u8 ata_dev_knobble(struct ata_port *ap)
{
        return ((ap->cbl == ATA_CBL_SATA) && (!ata_id_is_sata(ap->device->id)));
}

/**
 *      ata_dev_config - Run device specific handlers and check for
 *                       SATA->PATA bridges
 *      @ap: Bus
 *      @i:  Device
 *
 *      LOCKING:
 */

void ata_dev_config(struct ata_port *ap, unsigned int i)
{
        /* limit bridge transfers to udma5, 200 sectors */
        if (ata_dev_knobble(ap)) {
                printk(KERN_INFO "ata%u(%u): applying bridge limits\n",
                        ap->id, ap->device->devno);
                ap->udma_mask &= ATA_UDMA5;
                ap->host->max_sectors = ATA_MAX_SECTORS;
                ap->host->hostt->max_sectors = ATA_MAX_SECTORS;
                ap->device->flags |= ATA_DFLAG_LOCK_SECTORS;
        }

        if (ap->ops->dev_config)
                ap->ops->dev_config(ap, &ap->device[i]);
}

/**
 *      ata_bus_probe - Reset and probe ATA bus
 *      @ap: Bus to probe
 *
 *      Master ATA bus probing function.  Initiates a hardware-dependent
 *      bus reset, then attempts to identify any devices found on
 *      the bus.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 *      RETURNS:
 *      Zero on success, non-zero on error.
 */

static int ata_bus_probe(struct ata_port *ap)
{
        unsigned int i, found = 0;

        ap->ops->phy_reset(ap);
        if (ap->flags & ATA_FLAG_PORT_DISABLED)
                goto err_out;

        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                ata_dev_identify(ap, i);
                if (ata_dev_present(&ap->device[i])) {
                        found = 1;
                        ata_dev_config(ap,i);
                }
        }

        if ((!found) || (ap->flags & ATA_FLAG_PORT_DISABLED))
                goto err_out_disable;

        ata_set_mode(ap);
        if (ap->flags & ATA_FLAG_PORT_DISABLED)
                goto err_out_disable;

        return 0;

err_out_disable:
        ap->ops->port_disable(ap);
err_out:
        return -1;
}

/**
 *      ata_port_probe - Mark port as enabled
 *      @ap: Port for which we indicate enablement
 *
 *      Modify @ap data structure such that the system
 *      thinks that the entire port is enabled.
 *
 *      LOCKING: host_set lock, or some other form of
 *      serialization.
 */

void ata_port_probe(struct ata_port *ap)
{
        ap->flags &= ~ATA_FLAG_PORT_DISABLED;
}

/**
 *      __sata_phy_reset - Wake/reset a low-level SATA PHY
 *      @ap: SATA port associated with target SATA PHY.
 *
 *      This function issues commands to standard SATA Sxxx
 *      PHY registers, to wake up the phy (and device), and
 *      clear any reset condition.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 */
void __sata_phy_reset(struct ata_port *ap)
{
        u32 sstatus;
        unsigned long timeout = jiffies + (HZ * 5);

        if (ap->flags & ATA_FLAG_SATA_RESET) {
                /* issue phy wake/reset */
                scr_write_flush(ap, SCR_CONTROL, 0x301);
                /* Couldn't find anything in SATA I/II specs, but
                 * AHCI-1.1 10.4.2 says at least 1 ms. */
                mdelay(1);
        }
        scr_write_flush(ap, SCR_CONTROL, 0x300); /* phy wake/clear reset */

        /* wait for phy to become ready, if necessary */
        do {
                msleep(200);
                sstatus = scr_read(ap, SCR_STATUS);
                if ((sstatus & 0xf) != 1)
                        break;
        } while (time_before(jiffies, timeout));

        /* TODO: phy layer with polling, timeouts, etc. */
        if (sata_dev_present(ap))
                ata_port_probe(ap);
        else {
                sstatus = scr_read(ap, SCR_STATUS);
                printk(KERN_INFO "ata%u: no device found (phy stat %08x)\n",
                       ap->id, sstatus);
                ata_port_disable(ap);
        }

        if (ap->flags & ATA_FLAG_PORT_DISABLED)
                return;

        if (ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT)) {
                ata_port_disable(ap);
                return;
        }

        ap->cbl = ATA_CBL_SATA;
}

/**
 *      sata_phy_reset - Reset SATA bus.
 *      @ap: SATA port associated with target SATA PHY.
 *
 *      This function resets the SATA bus, and then probes
 *      the bus for devices.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 */
void sata_phy_reset(struct ata_port *ap)
{
        __sata_phy_reset(ap);
        if (ap->flags & ATA_FLAG_PORT_DISABLED)
                return;
        ata_bus_reset(ap);
}

/**
 *      ata_port_disable - Disable port.
 *      @ap: Port to be disabled.
 *
 *      Modify @ap data structure such that the system
 *      thinks that the entire port is disabled, and should
 *      never attempt to probe or communicate with devices
 *      on this port.
 *
 *      LOCKING: host_set lock, or some other form of
 *      serialization.
 */

void ata_port_disable(struct ata_port *ap)
{
        ap->device[0].class = ATA_DEV_NONE;
        ap->device[1].class = ATA_DEV_NONE;
        ap->flags |= ATA_FLAG_PORT_DISABLED;
}

static struct {
        unsigned int shift;
        u8 base;
} xfer_mode_classes[] = {
        { ATA_SHIFT_UDMA,       XFER_UDMA_0 },
        { ATA_SHIFT_MWDMA,      XFER_MW_DMA_0 },
        { ATA_SHIFT_PIO,        XFER_PIO_0 },
};

static inline u8 base_from_shift(unsigned int shift)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(xfer_mode_classes); i++)
                if (xfer_mode_classes[i].shift == shift)
                        return xfer_mode_classes[i].base;

        return 0xff;
}

static void ata_dev_set_mode(struct ata_port *ap, struct ata_device *dev)
{
        int ofs, idx;
        u8 base;

        if (!ata_dev_present(dev) || (ap->flags & ATA_FLAG_PORT_DISABLED))
                return;

        if (dev->xfer_shift == ATA_SHIFT_PIO)
                dev->flags |= ATA_DFLAG_PIO;

        ata_dev_set_xfermode(ap, dev);

        base = base_from_shift(dev->xfer_shift);
        ofs = dev->xfer_mode - base;
        idx = ofs + dev->xfer_shift;
        WARN_ON(idx >= ARRAY_SIZE(xfer_mode_str));

        DPRINTK("idx=%d xfer_shift=%u, xfer_mode=0x%x, base=0x%x, offset=%d\n",
                idx, dev->xfer_shift, (int)dev->xfer_mode, (int)base, ofs);

        printk(KERN_INFO "ata%u: dev %u configured for %s\n",
                ap->id, dev->devno, xfer_mode_str[idx]);
}

static int ata_host_set_pio(struct ata_port *ap)
{
        unsigned int mask;
        int x, i;
        u8 base, xfer_mode;

        mask = ata_get_mode_mask(ap, ATA_SHIFT_PIO);
        x = fgb(mask);
        if (x < 0) {
                printk(KERN_WARNING "ata%u: no PIO support\n", ap->id);
                return -1;
        }

        base = base_from_shift(ATA_SHIFT_PIO);
        xfer_mode = base + x;

        DPRINTK("base 0x%x xfer_mode 0x%x mask 0x%x x %d\n",
                (int)base, (int)xfer_mode, mask, x);

        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                struct ata_device *dev = &ap->device[i];
                if (ata_dev_present(dev)) {
                        dev->pio_mode = xfer_mode;
                        dev->xfer_mode = xfer_mode;
                        dev->xfer_shift = ATA_SHIFT_PIO;
                        if (ap->ops->set_piomode)
                                ap->ops->set_piomode(ap, dev);
                }
        }

        return 0;
}

static void ata_host_set_dma(struct ata_port *ap, u8 xfer_mode,
                            unsigned int xfer_shift)
{
        int i;

        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                struct ata_device *dev = &ap->device[i];
                if (ata_dev_present(dev)) {
                        dev->dma_mode = xfer_mode;
                        dev->xfer_mode = xfer_mode;
                        dev->xfer_shift = xfer_shift;
                        if (ap->ops->set_dmamode)
                                ap->ops->set_dmamode(ap, dev);
                }
        }
}

/**
 *      ata_set_mode - Program timings and issue SET FEATURES - XFER
 *      @ap: port on which timings will be programmed
 *
 *      Set ATA device disk transfer mode (PIO3, UDMA6, etc.).
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 */
static void ata_set_mode(struct ata_port *ap)
{
        unsigned int i, xfer_shift;
        u8 xfer_mode;
        int rc;

        /* step 1: always set host PIO timings */
        rc = ata_host_set_pio(ap);
        if (rc)
                goto err_out;

        /* step 2: choose the best data xfer mode */
        xfer_mode = xfer_shift = 0;
        rc = ata_choose_xfer_mode(ap, &xfer_mode, &xfer_shift);
        if (rc)
                goto err_out;

        /* step 3: if that xfer mode isn't PIO, set host DMA timings */
        if (xfer_shift != ATA_SHIFT_PIO)
                ata_host_set_dma(ap, xfer_mode, xfer_shift);

        /* step 4: update devices' xfer mode */
        ata_dev_set_mode(ap, &ap->device[0]);
        ata_dev_set_mode(ap, &ap->device[1]);

        if (ap->flags & ATA_FLAG_PORT_DISABLED)
                return;

        if (ap->ops->post_set_mode)
                ap->ops->post_set_mode(ap);

        for (i = 0; i < 2; i++) {
                struct ata_device *dev = &ap->device[i];
                ata_dev_set_protocol(dev);
        }

        return;

err_out:
        ata_port_disable(ap);
}

/**
 *      ata_busy_sleep - sleep until BSY clears, or timeout
 *      @ap: port containing status register to be polled
 *      @tmout_pat: impatience timeout
 *      @tmout: overall timeout
 *
 *      Sleep until ATA Status register bit BSY clears,
 *      or a timeout occurs.
 *
 *      LOCKING: None.
 *
 */

static unsigned int ata_busy_sleep (struct ata_port *ap,
                                    unsigned long tmout_pat,
                                    unsigned long tmout)
{
        unsigned long timer_start, timeout;
        u8 status;

        status = ata_busy_wait(ap, ATA_BUSY, 300);
        timer_start = jiffies;
        timeout = timer_start + tmout_pat;
        while ((status & ATA_BUSY) && (time_before(jiffies, timeout))) {
                msleep(50);
                status = ata_busy_wait(ap, ATA_BUSY, 3);
        }

        if (status & ATA_BUSY)
                printk(KERN_WARNING "ata%u is slow to respond, "
                       "please be patient\n", ap->id);

        timeout = timer_start + tmout;
        while ((status & ATA_BUSY) && (time_before(jiffies, timeout))) {
                msleep(50);
                status = ata_chk_status(ap);
        }

        if (status & ATA_BUSY) {
                printk(KERN_ERR "ata%u failed to respond (%lu secs)\n",
                       ap->id, tmout / HZ);
                return 1;
        }

        return 0;
}

static void ata_bus_post_reset(struct ata_port *ap, unsigned int devmask)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        unsigned int dev0 = devmask & (1 << 0);
        unsigned int dev1 = devmask & (1 << 1);
        unsigned long timeout;

        /* if device 0 was found in ata_devchk, wait for its
         * BSY bit to clear
         */
        if (dev0)
                ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);

        /* if device 1 was found in ata_devchk, wait for
         * register access, then wait for BSY to clear
         */
        timeout = jiffies + ATA_TMOUT_BOOT;
        while (dev1) {
                u8 nsect, lbal;

                ap->ops->dev_select(ap, 1);
                if (ap->flags & ATA_FLAG_MMIO) {
                        nsect = readb((void __iomem *) ioaddr->nsect_addr);
                        lbal = readb((void __iomem *) ioaddr->lbal_addr);
                } else {
                        nsect = inb(ioaddr->nsect_addr);
                        lbal = inb(ioaddr->lbal_addr);
                }
                if ((nsect == 1) && (lbal == 1))
                        break;
                if (time_after(jiffies, timeout)) {
                        dev1 = 0;
                        break;
                }
                msleep(50);     /* give drive a breather */
        }
        if (dev1)
                ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);

        /* is all this really necessary? */
        ap->ops->dev_select(ap, 0);
        if (dev1)
                ap->ops->dev_select(ap, 1);
        if (dev0)
                ap->ops->dev_select(ap, 0);
}

/**
 *      ata_bus_edd - Issue EXECUTE DEVICE DIAGNOSTIC command.
 *      @ap: Port to reset and probe
 *
 *      Use the EXECUTE DEVICE DIAGNOSTIC command to reset and
 *      probe the bus.  Not often used these days.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 */

static unsigned int ata_bus_edd(struct ata_port *ap)
{
        struct ata_taskfile tf;

        /* set up execute-device-diag (bus reset) taskfile */
        /* also, take interrupts to a known state (disabled) */
        DPRINTK("execute-device-diag\n");
        ata_tf_init(ap, &tf, 0);
        tf.ctl |= ATA_NIEN;
        tf.command = ATA_CMD_EDD;
        tf.protocol = ATA_PROT_NODATA;

        /* do bus reset */
        ata_tf_to_host(ap, &tf);

        /* spec says at least 2ms.  but who knows with those
         * crazy ATAPI devices...
         */
        msleep(150);

        return ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);
}

static unsigned int ata_bus_softreset(struct ata_port *ap,
                                      unsigned int devmask)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;

        DPRINTK("ata%u: bus reset via SRST\n", ap->id);

        /* software reset.  causes dev0 to be selected */
        if (ap->flags & ATA_FLAG_MMIO) {
                writeb(ap->ctl, (void __iomem *) ioaddr->ctl_addr);
                udelay(20);     /* FIXME: flush */
                writeb(ap->ctl | ATA_SRST, (void __iomem *) ioaddr->ctl_addr);
                udelay(20);     /* FIXME: flush */
                writeb(ap->ctl, (void __iomem *) ioaddr->ctl_addr);
        } else {
                outb(ap->ctl, ioaddr->ctl_addr);
                udelay(10);
                outb(ap->ctl | ATA_SRST, ioaddr->ctl_addr);
                udelay(10);
                outb(ap->ctl, ioaddr->ctl_addr);
        }

        /* spec mandates ">= 2ms" before checking status.
         * We wait 150ms, because that was the magic delay used for
         * ATAPI devices in Hale Landis's ATADRVR, for the period of time
         * between when the ATA command register is written, and then
         * status is checked.  Because waiting for "a while" before
         * checking status is fine, post SRST, we perform this magic
         * delay here as well.
         */
        msleep(150);

        ata_bus_post_reset(ap, devmask);

        return 0;
}

/**
 *      ata_bus_reset - reset host port and associated ATA channel
 *      @ap: port to reset
 *
 *      This is typically the first time we actually start issuing
 *      commands to the ATA channel.  We wait for BSY to clear, then
 *      issue EXECUTE DEVICE DIAGNOSTIC command, polling for its
 *      result.  Determine what devices, if any, are on the channel
 *      by looking at the device 0/1 error register.  Look at the signature
 *      stored in each device's taskfile registers, to determine if
 *      the device is ATA or ATAPI.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *      Obtains host_set lock.
 *
 *      SIDE EFFECTS:
 *      Sets ATA_FLAG_PORT_DISABLED if bus reset fails.
 */

void ata_bus_reset(struct ata_port *ap)
{
        struct ata_ioports *ioaddr = &ap->ioaddr;
        unsigned int slave_possible = ap->flags & ATA_FLAG_SLAVE_POSS;
        u8 err;
        unsigned int dev0, dev1 = 0, rc = 0, devmask = 0;

        DPRINTK("ENTER, host %u, port %u\n", ap->id, ap->port_no);

        /* determine if device 0/1 are present */
        if (ap->flags & ATA_FLAG_SATA_RESET)
                dev0 = 1;
        else {
                dev0 = ata_devchk(ap, 0);
                if (slave_possible)
                        dev1 = ata_devchk(ap, 1);
        }

        if (dev0)
                devmask |= (1 << 0);
        if (dev1)
                devmask |= (1 << 1);

        /* select device 0 again */
        ap->ops->dev_select(ap, 0);

        /* issue bus reset */
        if (ap->flags & ATA_FLAG_SRST)
                rc = ata_bus_softreset(ap, devmask);
        else if ((ap->flags & ATA_FLAG_SATA_RESET) == 0) {
                /* set up device control */
                if (ap->flags & ATA_FLAG_MMIO)
                        writeb(ap->ctl, (void __iomem *) ioaddr->ctl_addr);
                else
                        outb(ap->ctl, ioaddr->ctl_addr);
                rc = ata_bus_edd(ap);
        }

        if (rc)
                goto err_out;

        /*
         * determine by signature whether we have ATA or ATAPI devices
         */
        err = ata_dev_try_classify(ap, 0);
        if ((slave_possible) && (err != 0x81))
                ata_dev_try_classify(ap, 1);

        /* re-enable interrupts */
        if (ap->ioaddr.ctl_addr)        /* FIXME: hack. create a hook instead */
                ata_irq_on(ap);

        /* is double-select really necessary? */
        if (ap->device[1].class != ATA_DEV_NONE)
                ap->ops->dev_select(ap, 1);
        if (ap->device[0].class != ATA_DEV_NONE)
                ap->ops->dev_select(ap, 0);

        /* if no devices were detected, disable this port */
        if ((ap->device[0].class == ATA_DEV_NONE) &&
            (ap->device[1].class == ATA_DEV_NONE))
                goto err_out;

        if (ap->flags & (ATA_FLAG_SATA_RESET | ATA_FLAG_SRST)) {
                /* set up device control for ATA_FLAG_SATA_RESET */
                if (ap->flags & ATA_FLAG_MMIO)
                        writeb(ap->ctl, (void __iomem *) ioaddr->ctl_addr);
                else
                        outb(ap->ctl, ioaddr->ctl_addr);
        }

        DPRINTK("EXIT\n");
        return;

err_out:
        printk(KERN_ERR "ata%u: disabling port\n", ap->id);
        ap->ops->port_disable(ap);

        DPRINTK("EXIT\n");
}

static void ata_pr_blacklisted(struct ata_port *ap, struct ata_device *dev)
{
        printk(KERN_WARNING "ata%u: dev %u is on DMA blacklist, disabling DMA\n",
                ap->id, dev->devno);
}

static const char * ata_dma_blacklist [] = {
        "WDC AC11000H",
        "WDC AC22100H",
        "WDC AC32500H",
        "WDC AC33100H",
        "WDC AC31600H",
        "WDC AC32100H",
        "WDC AC23200L",
        "Compaq CRD-8241B",
        "CRD-8400B",
        "CRD-8480B",
        "CRD-8482B",
        "CRD-84",
        "SanDisk SDP3B",
        "SanDisk SDP3B-64",
        "SANYO CD-ROM CRD",
        "HITACHI CDR-8",
        "HITACHI CDR-8335",
        "HITACHI CDR-8435",
        "Toshiba CD-ROM XM-6202B",
        "TOSHIBA CD-ROM XM-1702BC",
        "CD-532E-A",
        "E-IDE CD-ROM CR-840",
        "CD-ROM Drive/F5A",
        "WPI CDD-820",
        "SAMSUNG CD-ROM SC-148C",
        "SAMSUNG CD-ROM SC",
        "SanDisk SDP3B-64",
        "ATAPI CD-ROM DRIVE 40X MAXIMUM",
        "_NEC DV5800A",
};

static int ata_dma_blacklisted(struct ata_port *ap, struct ata_device *dev)
{
        unsigned char model_num[40];
        char *s;
        unsigned int len;
        int i;

        ata_dev_id_string(dev->id, model_num, ATA_ID_PROD_OFS,
                          sizeof(model_num));
        s = &model_num[0];
        len = strnlen(s, sizeof(model_num));

        /* ATAPI specifies that empty space is blank-filled; remove blanks */
        while ((len > 0) && (s[len - 1] == ' ')) {
                len--;
                s[len] = 0;
        }

        for (i = 0; i < ARRAY_SIZE(ata_dma_blacklist); i++)
                if (!strncmp(ata_dma_blacklist[i], s, len))
                        return 1;

        return 0;
}

static unsigned int ata_get_mode_mask(struct ata_port *ap, int shift)
{
        struct ata_device *master, *slave;
        unsigned int mask;

        master = &ap->device[0];
        slave = &ap->device[1];

        assert (ata_dev_present(master) || ata_dev_present(slave));

        if (shift == ATA_SHIFT_UDMA) {
                mask = ap->udma_mask;
                if (ata_dev_present(master)) {
                        mask &= (master->id[ATA_ID_UDMA_MODES] & 0xff);
                        if (ata_dma_blacklisted(ap, master)) {
                                mask = 0;
                                ata_pr_blacklisted(ap, master);
                        }
                }
                if (ata_dev_present(slave)) {
                        mask &= (slave->id[ATA_ID_UDMA_MODES] & 0xff);
                        if (ata_dma_blacklisted(ap, slave)) {
                                mask = 0;
                                ata_pr_blacklisted(ap, slave);
                        }
                }
        }
        else if (shift == ATA_SHIFT_MWDMA) {
                mask = ap->mwdma_mask;
                if (ata_dev_present(master)) {
                        mask &= (master->id[ATA_ID_MWDMA_MODES] & 0x07);
                        if (ata_dma_blacklisted(ap, master)) {
                                mask = 0;
                                ata_pr_blacklisted(ap, master);
                        }
                }
                if (ata_dev_present(slave)) {
                        mask &= (slave->id[ATA_ID_MWDMA_MODES] & 0x07);
                        if (ata_dma_blacklisted(ap, slave)) {
                                mask = 0;
                                ata_pr_blacklisted(ap, slave);
                        }
                }
        }
        else if (shift == ATA_SHIFT_PIO) {
                mask = ap->pio_mask;
                if (ata_dev_present(master)) {
                        /* spec doesn't return explicit support for
                         * PIO0-2, so we fake it
                         */
                        u16 tmp_mode = master->id[ATA_ID_PIO_MODES] & 0x03;
                        tmp_mode <<= 3;
                        tmp_mode |= 0x7;
                        mask &= tmp_mode;
                }
                if (ata_dev_present(slave)) {
                        /* spec doesn't return explicit support for
                         * PIO0-2, so we fake it
                         */
                        u16 tmp_mode = slave->id[ATA_ID_PIO_MODES] & 0x03;
                        tmp_mode <<= 3;
                        tmp_mode |= 0x7;
                        mask &= tmp_mode;
                }
        }
        else {
                mask = 0xffffffff; /* shut up compiler warning */
                BUG();
        }

        return mask;
}

/* find greatest bit */
static int fgb(u32 bitmap)
{
        unsigned int i;
        int x = -1;

        for (i = 0; i < 32; i++)
                if (bitmap & (1 << i))
                        x = i;

        return x;
}

/**
 *      ata_choose_xfer_mode - attempt to find best transfer mode
 *      @ap: Port for which an xfer mode will be selected
 *      @xfer_mode_out: (output) SET FEATURES - XFER MODE code
 *      @xfer_shift_out: (output) bit shift that selects this mode
 *
 *      Based on host and device capabilities, determine the
 *      maximum transfer mode that is amenable to all.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 *
 *      RETURNS:
 *      Zero on success, negative on error.
 */

static int ata_choose_xfer_mode(struct ata_port *ap,
                                u8 *xfer_mode_out,
                                unsigned int *xfer_shift_out)
{
        unsigned int mask, shift;
        int x, i;

        for (i = 0; i < ARRAY_SIZE(xfer_mode_classes); i++) {
                shift = xfer_mode_classes[i].shift;
                mask = ata_get_mode_mask(ap, shift);

                x = fgb(mask);
                if (x >= 0) {
                        *xfer_mode_out = xfer_mode_classes[i].base + x;
                        *xfer_shift_out = shift;
                        return 0;
                }
        }

        return -1;
}

/**
 *      ata_dev_set_xfermode - Issue SET FEATURES - XFER MODE command
 *      @ap: Port associated with device @dev
 *      @dev: Device to which command will be sent
 *
 *      Issue SET FEATURES - XFER MODE command to device @dev
 *      on port @ap.
 *
 *      LOCKING:
 *      PCI/etc. bus probe sem.
 */

static void ata_dev_set_xfermode(struct ata_port *ap, struct ata_device *dev)
{
        DECLARE_COMPLETION(wait);
        struct ata_queued_cmd *qc;
        int rc;
        unsigned long flags;

        /* set up set-features taskfile */
        DPRINTK("set features - xfer mode\n");

        qc = ata_qc_new_init(ap, dev);
        BUG_ON(qc == NULL);

        qc->tf.command = ATA_CMD_SET_FEATURES;
        qc->tf.feature = SETFEATURES_XFER;
        qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        qc->tf.protocol = ATA_PROT_NODATA;
        qc->tf.nsect = dev->xfer_mode;

        qc->waiting = &wait;
        qc->complete_fn = ata_qc_complete_noop;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        rc = ata_qc_issue(qc);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        if (rc)
                ata_port_disable(ap);
        else
                wait_for_completion(&wait);

        DPRINTK("EXIT\n");
}

/**
 *      ata_dev_init_params - Issue INIT DEV PARAMS command
 *      @ap: Port associated with device @dev
 *      @dev: Device to which command will be sent
 *
 *      LOCKING:
 */

static void ata_dev_init_params(struct ata_port *ap, struct ata_device *dev)
{
        DECLARE_COMPLETION(wait);
        struct ata_queued_cmd *qc;
        int rc;
        unsigned long flags;
        u16 sectors = dev->id[6];
        u16 heads   = dev->id[3];

        /* Number of sectors per track 1-255. Number of heads 1-16 */
        if (sectors < 1 || sectors > 255 || heads < 1 || heads > 16)
                return;

        /* set up init dev params taskfile */
        DPRINTK("init dev params \n");

        qc = ata_qc_new_init(ap, dev);
        BUG_ON(qc == NULL);

        qc->tf.command = ATA_CMD_INIT_DEV_PARAMS;
        qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        qc->tf.protocol = ATA_PROT_NODATA;
        qc->tf.nsect = sectors;
        qc->tf.device |= (heads - 1) & 0x0f; /* max head = num. of heads - 1 */

        qc->waiting = &wait;
        qc->complete_fn = ata_qc_complete_noop;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        rc = ata_qc_issue(qc);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        if (rc)
                ata_port_disable(ap);
        else
                wait_for_completion(&wait);

        DPRINTK("EXIT\n");
}

/**
 *      ata_sg_clean - Unmap DMA memory associated with command
 *      @qc: Command containing DMA memory to be released
 *
 *      Unmap all mapped DMA memory associated with this command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_sg_clean(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct scatterlist *sg = qc->sg;
        int dir = qc->dma_dir;

        assert(qc->flags & ATA_QCFLAG_DMAMAP);
        assert(sg != NULL);

        if (qc->flags & ATA_QCFLAG_SINGLE)
                assert(qc->n_elem == 1);

        DPRINTK("unmapping %u sg elements\n", qc->n_elem);

        if (qc->flags & ATA_QCFLAG_SG)
                dma_unmap_sg(ap->host_set->dev, sg, qc->n_elem, dir);
        else
                dma_unmap_single(ap->host_set->dev, sg_dma_address(&sg[0]),
                                 sg_dma_len(&sg[0]), dir);

        qc->flags &= ~ATA_QCFLAG_DMAMAP;
        qc->sg = NULL;
}

/**
 *      ata_fill_sg - Fill PCI IDE PRD table
 *      @qc: Metadata associated with taskfile to be transferred
 *
 *      Fill PCI IDE PRD (scatter-gather) table with segments
 *      associated with the current disk command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 */
static void ata_fill_sg(struct ata_queued_cmd *qc)
{
        struct scatterlist *sg = qc->sg;
        struct ata_port *ap = qc->ap;
        unsigned int idx, nelem;

        assert(sg != NULL);
        assert(qc->n_elem > 0);

        idx = 0;
        for (nelem = qc->n_elem; nelem; nelem--,sg++) {
                u32 addr, offset;
                u32 sg_len, len;

                /* determine if physical DMA addr spans 64K boundary.
                 * Note h/w doesn't support 64-bit, so we unconditionally
                 * truncate dma_addr_t to u32.
                 */
                addr = (u32) sg_dma_address(sg);
                sg_len = sg_dma_len(sg);

                while (sg_len) {
                        offset = addr & 0xffff;
                        len = sg_len;
                        if ((offset + sg_len) > 0x10000)
                                len = 0x10000 - offset;

                        ap->prd[idx].addr = cpu_to_le32(addr);
                        ap->prd[idx].flags_len = cpu_to_le32(len & 0xffff);
                        VPRINTK("PRD[%u] = (0x%X, 0x%X)\n", idx, addr, len);

                        idx++;
                        sg_len -= len;
                        addr += len;
                }
        }

        if (idx)
                ap->prd[idx - 1].flags_len |= cpu_to_le32(ATA_PRD_EOT);
}
/**
 *      ata_check_atapi_dma - Check whether ATAPI DMA can be supported
 *      @qc: Metadata associated with taskfile to check
 *
 *      Allow low-level driver to filter ATA PACKET commands, returning
 *      a status indicating whether or not it is OK to use DMA for the
 *      supplied PACKET command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS: 0 when ATAPI DMA can be used
 *               nonzero otherwise
 */
int ata_check_atapi_dma(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        int rc = 0; /* Assume ATAPI DMA is OK by default */

        if (ap->ops->check_atapi_dma)
                rc = ap->ops->check_atapi_dma(qc);

        return rc;
}
/**
 *      ata_qc_prep - Prepare taskfile for submission
 *      @qc: Metadata associated with taskfile to be prepared
 *
 *      Prepare ATA taskfile for submission.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */
void ata_qc_prep(struct ata_queued_cmd *qc)
{
        if (!(qc->flags & ATA_QCFLAG_DMAMAP))
                return;

        ata_fill_sg(qc);
}

/**
 *      ata_sg_init_one - Associate command with memory buffer
 *      @qc: Command to be associated
 *      @buf: Memory buffer
 *      @buflen: Length of memory buffer, in bytes.
 *
 *      Initialize the data-related elements of queued_cmd @qc
 *      to point to a single memory buffer, @buf of byte length @buflen.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_sg_init_one(struct ata_queued_cmd *qc, void *buf, unsigned int buflen)
{
        struct scatterlist *sg;

        qc->flags |= ATA_QCFLAG_SINGLE;

        memset(&qc->sgent, 0, sizeof(qc->sgent));
        qc->sg = &qc->sgent;
        qc->n_elem = 1;
        qc->buf_virt = buf;

        sg = qc->sg;
        sg->page = virt_to_page(buf);
        sg->offset = (unsigned long) buf & ~PAGE_MASK;
        sg->length = buflen;
}

/**
 *      ata_sg_init - Associate command with scatter-gather table.
 *      @qc: Command to be associated
 *      @sg: Scatter-gather table.
 *      @n_elem: Number of elements in s/g table.
 *
 *      Initialize the data-related elements of queued_cmd @qc
 *      to point to a scatter-gather table @sg, containing @n_elem
 *      elements.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg,
                 unsigned int n_elem)
{
        qc->flags |= ATA_QCFLAG_SG;
        qc->sg = sg;
        qc->n_elem = n_elem;
}

/**
 *      ata_sg_setup_one - DMA-map the memory buffer associated with a command.
 *      @qc: Command with memory buffer to be mapped.
 *
 *      DMA-map the memory buffer associated with queued_cmd @qc.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, negative on error.
 */

static int ata_sg_setup_one(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        int dir = qc->dma_dir;
        struct scatterlist *sg = qc->sg;
        dma_addr_t dma_address;

        dma_address = dma_map_single(ap->host_set->dev, qc->buf_virt,
                                     sg->length, dir);
        if (dma_mapping_error(dma_address))
                return -1;

        sg_dma_address(sg) = dma_address;
        sg_dma_len(sg) = sg->length;

        DPRINTK("mapped buffer of %d bytes for %s\n", sg_dma_len(sg),
                qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

        return 0;
}

/**
 *      ata_sg_setup - DMA-map the scatter-gather table associated with a command.
 *      @qc: Command with scatter-gather table to be mapped.
 *
 *      DMA-map the scatter-gather table associated with queued_cmd @qc.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, negative on error.
 *
 */

static int ata_sg_setup(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct scatterlist *sg = qc->sg;
        int n_elem, dir;

        VPRINTK("ENTER, ata%u\n", ap->id);
        assert(qc->flags & ATA_QCFLAG_SG);

        dir = qc->dma_dir;
        n_elem = dma_map_sg(ap->host_set->dev, sg, qc->n_elem, dir);
        if (n_elem < 1)
                return -1;

        DPRINTK("%d sg elements mapped\n", n_elem);

        qc->n_elem = n_elem;

        return 0;
}

/**
 *      ata_poll_qc_complete - turn irq back on and finish qc
 *      @qc: Command to complete
 *      @drv_stat: ATA status register content
 *
 *      LOCKING:
 *      None.  (grabs host lock)
 */

void ata_poll_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
{
        struct ata_port *ap = qc->ap;
        unsigned long flags;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        ap->flags &= ~ATA_FLAG_NOINTR;
        ata_irq_on(ap);
        ata_qc_complete(qc, drv_stat);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);
}

/**
 *      ata_pio_poll -
 *      @ap:
 *
 *      LOCKING:
 *      None.  (executing in kernel thread context)
 *
 *      RETURNS:
 *
 */

static unsigned long ata_pio_poll(struct ata_port *ap)
{
        u8 status;
        unsigned int poll_state = PIO_ST_UNKNOWN;
        unsigned int reg_state = PIO_ST_UNKNOWN;
        const unsigned int tmout_state = PIO_ST_TMOUT;

        switch (ap->pio_task_state) {
        case PIO_ST:
        case PIO_ST_POLL:
                poll_state = PIO_ST_POLL;
                reg_state = PIO_ST;
                break;
        case PIO_ST_LAST:
        case PIO_ST_LAST_POLL:
                poll_state = PIO_ST_LAST_POLL;
                reg_state = PIO_ST_LAST;
                break;
        default:
                BUG();
                break;
        }

        status = ata_chk_status(ap);
        if (status & ATA_BUSY) {
                if (time_after(jiffies, ap->pio_task_timeout)) {
                        ap->pio_task_state = tmout_state;
                        return 0;
                }
                ap->pio_task_state = poll_state;
                return ATA_SHORT_PAUSE;
        }

        ap->pio_task_state = reg_state;
        return 0;
}

/**
 *      ata_pio_complete -
 *      @ap:
 *
 *      LOCKING:
 *      None.  (executing in kernel thread context)
 */

static void ata_pio_complete (struct ata_port *ap)
{
        struct ata_queued_cmd *qc;
        u8 drv_stat;

        /*
         * This is purely heuristic.  This is a fast path.  Sometimes when
         * we enter, BSY will be cleared in a chk-status or two.  If not,
         * the drive is probably seeking or something.  Snooze for a couple
         * msecs, then chk-status again.  If still busy, fall back to
         * PIO_ST_POLL state.
         */
        drv_stat = ata_busy_wait(ap, ATA_BUSY | ATA_DRQ, 10);
        if (drv_stat & (ATA_BUSY | ATA_DRQ)) {
                msleep(2);
                drv_stat = ata_busy_wait(ap, ATA_BUSY | ATA_DRQ, 10);
                if (drv_stat & (ATA_BUSY | ATA_DRQ)) {
                        ap->pio_task_state = PIO_ST_LAST_POLL;
                        ap->pio_task_timeout = jiffies + ATA_TMOUT_PIO;
                        return;
                }
        }

        drv_stat = ata_wait_idle(ap);
        if (!ata_ok(drv_stat)) {
                ap->pio_task_state = PIO_ST_ERR;
                return;
        }

        qc = ata_qc_from_tag(ap, ap->active_tag);
        assert(qc != NULL);

        ap->pio_task_state = PIO_ST_IDLE;

        ata_poll_qc_complete(qc, drv_stat);
}


/**
 *      swap_buf_le16 -
 *      @buf:  Buffer to swap
 *      @buf_words:  Number of 16-bit words in buffer.
 *
 *      Swap halves of 16-bit words if needed to convert from
 *      little-endian byte order to native cpu byte order, or
 *      vice-versa.
 *
 *      LOCKING:
 */
void swap_buf_le16(u16 *buf, unsigned int buf_words)
{
#ifdef __BIG_ENDIAN
        unsigned int i;

        for (i = 0; i < buf_words; i++)
                buf[i] = le16_to_cpu(buf[i]);
#endif /* __BIG_ENDIAN */
}

/**
 *      ata_mmio_data_xfer - Transfer data by MMIO
 *      @ap: port to read/write
 *      @buf: data buffer
 *      @buflen: buffer length
 *      @do_write: read/write
 *
 *      Transfer data from/to the device data register by MMIO.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 */

static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
                               unsigned int buflen, int write_data)
{
        unsigned int i;
        unsigned int words = buflen >> 1;
        u16 *buf16 = (u16 *) buf;
        void __iomem *mmio = (void __iomem *)ap->ioaddr.data_addr;

        /* Transfer multiple of 2 bytes */
        if (write_data) {
                for (i = 0; i < words; i++)
                        writew(le16_to_cpu(buf16[i]), mmio);
        } else {
                for (i = 0; i < words; i++)
                        buf16[i] = cpu_to_le16(readw(mmio));
        }

        /* Transfer trailing 1 byte, if any. */
        if (unlikely(buflen & 0x01)) {
                u16 align_buf[1] = { 0 };
                unsigned char *trailing_buf = buf + buflen - 1;

                if (write_data) {
                        memcpy(align_buf, trailing_buf, 1);
                        writew(le16_to_cpu(align_buf[0]), mmio);
                } else {
                        align_buf[0] = cpu_to_le16(readw(mmio));
                        memcpy(trailing_buf, align_buf, 1);
                }
        }
}

/**
 *      ata_pio_data_xfer - Transfer data by PIO
 *      @ap: port to read/write
 *      @buf: data buffer
 *      @buflen: buffer length
 *      @do_write: read/write
 *
 *      Transfer data from/to the device data register by PIO.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 */

static void ata_pio_data_xfer(struct ata_port *ap, unsigned char *buf,
                              unsigned int buflen, int write_data)
{
        unsigned int words = buflen >> 1;

        /* Transfer multiple of 2 bytes */
        if (write_data)
                outsw(ap->ioaddr.data_addr, buf, words);
        else
                insw(ap->ioaddr.data_addr, buf, words);

        /* Transfer trailing 1 byte, if any. */
        if (unlikely(buflen & 0x01)) {
                u16 align_buf[1] = { 0 };
                unsigned char *trailing_buf = buf + buflen - 1;

                if (write_data) {
                        memcpy(align_buf, trailing_buf, 1);
                        outw(le16_to_cpu(align_buf[0]), ap->ioaddr.data_addr);
                } else {
                        align_buf[0] = cpu_to_le16(inw(ap->ioaddr.data_addr));
                        memcpy(trailing_buf, align_buf, 1);
                }
        }
}

/**
 *      ata_data_xfer - Transfer data from/to the data register.
 *      @ap: port to read/write
 *      @buf: data buffer
 *      @buflen: buffer length
 *      @do_write: read/write
 *
 *      Transfer data from/to the device data register.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 */

static void ata_data_xfer(struct ata_port *ap, unsigned char *buf,
                          unsigned int buflen, int do_write)
{
        if (ap->flags & ATA_FLAG_MMIO)
                ata_mmio_data_xfer(ap, buf, buflen, do_write);
        else
                ata_pio_data_xfer(ap, buf, buflen, do_write);
}

/**
 *      ata_pio_sector - Transfer ATA_SECT_SIZE (512 bytes) of data.
 *      @qc: Command on going
 *
 *      Transfer ATA_SECT_SIZE of data from/to the ATA device.
 *
 *      LOCKING:
 *      Inherited from caller.
 */

static void ata_pio_sector(struct ata_queued_cmd *qc)
{
        int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
        struct scatterlist *sg = qc->sg;
        struct ata_port *ap = qc->ap;
        struct page *page;
        unsigned int offset;
        unsigned char *buf;

        if (qc->cursect == (qc->nsect - 1))
                ap->pio_task_state = PIO_ST_LAST;

        page = sg[qc->cursg].page;
        offset = sg[qc->cursg].offset + qc->cursg_ofs * ATA_SECT_SIZE;

        /* get the current page and offset */
        page = nth_page(page, (offset >> PAGE_SHIFT));
        offset %= PAGE_SIZE;

        buf = kmap(page) + offset;

        qc->cursect++;
        qc->cursg_ofs++;

        if ((qc->cursg_ofs * ATA_SECT_SIZE) == (&sg[qc->cursg])->length) {
                qc->cursg++;
                qc->cursg_ofs = 0;
        }

        DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

        /* do the actual data transfer */
        do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
        ata_data_xfer(ap, buf, ATA_SECT_SIZE, do_write);

        kunmap(page);
}

/**
 *      __atapi_pio_bytes - Transfer data from/to the ATAPI device.
 *      @qc: Command on going
 *      @bytes: number of bytes
 *
 *      Transfer Transfer data from/to the ATAPI device.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 */

static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
{
        int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
        struct scatterlist *sg = qc->sg;
        struct ata_port *ap = qc->ap;
        struct page *page;
        unsigned char *buf;
        unsigned int offset, count;

        if (qc->curbytes + bytes >= qc->nbytes)
                ap->pio_task_state = PIO_ST_LAST;

next_sg:
        if (unlikely(qc->cursg >= qc->n_elem)) {
                /* 
                 * The end of qc->sg is reached and the device expects
                 * more data to transfer. In order not to overrun qc->sg
                 * and fulfill length specified in the byte count register,
                 *    - for read case, discard trailing data from the device
                 *    - for write case, padding zero data to the device
                 */
                u16 pad_buf[1] = { 0 };
                unsigned int words = bytes >> 1;
                unsigned int i;

                if (words) /* warning if bytes > 1 */
                        printk(KERN_WARNING "ata%u: %u bytes trailing data\n", 
                               ap->id, bytes);

                for (i = 0; i < words; i++)
                        ata_data_xfer(ap, (unsigned char*)pad_buf, 2, do_write);

                ap->pio_task_state = PIO_ST_LAST;
                return;
        }

        sg = &qc->sg[qc->cursg];

        page = sg->page;
        offset = sg->offset + qc->cursg_ofs;

        /* get the current page and offset */
        page = nth_page(page, (offset >> PAGE_SHIFT));
        offset %= PAGE_SIZE;

        /* don't overrun current sg */
        count = min(sg->length - qc->cursg_ofs, bytes);

        /* don't cross page boundaries */
        count = min(count, (unsigned int)PAGE_SIZE - offset);

        buf = kmap(page) + offset;

        bytes -= count;
        qc->curbytes += count;
        qc->cursg_ofs += count;

        if (qc->cursg_ofs == sg->length) {
                qc->cursg++;
                qc->cursg_ofs = 0;
        }

        DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

        /* do the actual data transfer */
        ata_data_xfer(ap, buf, count, do_write);

        kunmap(page);

        if (bytes)
                goto next_sg;
}

/**
 *      atapi_pio_bytes - Transfer data from/to the ATAPI device.
 *      @qc: Command on going
 *
 *      Transfer Transfer data from/to the ATAPI device.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 */

static void atapi_pio_bytes(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct ata_device *dev = qc->dev;
        unsigned int ireason, bc_lo, bc_hi, bytes;
        int i_write, do_write = (qc->tf.flags & ATA_TFLAG_WRITE) ? 1 : 0;

        ap->ops->tf_read(ap, &qc->tf);
        ireason = qc->tf.nsect;
        bc_lo = qc->tf.lbam;
        bc_hi = qc->tf.lbah;
        bytes = (bc_hi << 8) | bc_lo;

        /* shall be cleared to zero, indicating xfer of data */
        if (ireason & (1 << 0))
                goto err_out;

        /* make sure transfer direction matches expected */
        i_write = ((ireason & (1 << 1)) == 0) ? 1 : 0;
        if (do_write != i_write)
                goto err_out;

        __atapi_pio_bytes(qc, bytes);

        return;

err_out:
        printk(KERN_INFO "ata%u: dev %u: ATAPI check failed\n",
              ap->id, dev->devno);
        ap->pio_task_state = PIO_ST_ERR;
}

/**
 *      ata_pio_sector -
 *      @ap:
 *
 *      LOCKING:
 *      None.  (executing in kernel thread context)
 */

static void ata_pio_block(struct ata_port *ap)
{
        struct ata_queued_cmd *qc;
        u8 status;

        /*
         * This is purely hueristic.  This is a fast path.
         * Sometimes when we enter, BSY will be cleared in
         * a chk-status or two.  If not, the drive is probably seeking
         * or something.  Snooze for a couple msecs, then
         * chk-status again.  If still busy, fall back to
         * PIO_ST_POLL state.
         */
        status = ata_busy_wait(ap, ATA_BUSY, 5);
        if (status & ATA_BUSY) {
                msleep(2);
                status = ata_busy_wait(ap, ATA_BUSY, 10);
                if (status & ATA_BUSY) {
                        ap->pio_task_state = PIO_ST_POLL;
                        ap->pio_task_timeout = jiffies + ATA_TMOUT_PIO;
                        return;
                }
        }

        qc = ata_qc_from_tag(ap, ap->active_tag);
        assert(qc != NULL);

        if (is_atapi_taskfile(&qc->tf)) {
                /* no more data to transfer or unsupported ATAPI command */
                if ((status & ATA_DRQ) == 0) {
                        ap->pio_task_state = PIO_ST_IDLE;

                        ata_poll_qc_complete(qc, status);
                        return;
                }

                atapi_pio_bytes(qc);
        } else {
                /* handle BSY=0, DRQ=0 as error */
                if ((status & ATA_DRQ) == 0) {
                        ap->pio_task_state = PIO_ST_ERR;
                        return;
                }

                ata_pio_sector(qc);
        }
}

static void ata_pio_error(struct ata_port *ap)
{
        struct ata_queued_cmd *qc;
        u8 drv_stat;

        qc = ata_qc_from_tag(ap, ap->active_tag);
        assert(qc != NULL);

        drv_stat = ata_chk_status(ap);
        printk(KERN_WARNING "ata%u: PIO error, drv_stat 0x%x\n",
               ap->id, drv_stat);

        ap->pio_task_state = PIO_ST_IDLE;

        ata_poll_qc_complete(qc, drv_stat | ATA_ERR);
}

static void ata_pio_task(void *_data)
{
        struct ata_port *ap = _data;
        unsigned long timeout = 0;

        switch (ap->pio_task_state) {
        case PIO_ST_IDLE:
                return;

        case PIO_ST:
                ata_pio_block(ap);
                break;

        case PIO_ST_LAST:
                ata_pio_complete(ap);
                break;

        case PIO_ST_POLL:
        case PIO_ST_LAST_POLL:
                timeout = ata_pio_poll(ap);
                break;

        case PIO_ST_TMOUT:
        case PIO_ST_ERR:
                ata_pio_error(ap);
                return;
        }

        if (timeout)
                queue_delayed_work(ata_wq, &ap->pio_task,
                                   timeout);
        else
                queue_work(ata_wq, &ap->pio_task);
}

static void atapi_request_sense(struct ata_port *ap, struct ata_device *dev,
                                struct scsi_cmnd *cmd)
{
        DECLARE_COMPLETION(wait);
        struct ata_queued_cmd *qc;
        unsigned long flags;
        int rc;

        DPRINTK("ATAPI request sense\n");

        qc = ata_qc_new_init(ap, dev);
        BUG_ON(qc == NULL);

        /* FIXME: is this needed? */
        memset(cmd->sense_buffer, 0, sizeof(cmd->sense_buffer));

        ata_sg_init_one(qc, cmd->sense_buffer, sizeof(cmd->sense_buffer));
        qc->dma_dir = DMA_FROM_DEVICE;

        memset(&qc->cdb, 0, ap->cdb_len);
        qc->cdb[0] = REQUEST_SENSE;
        qc->cdb[4] = SCSI_SENSE_BUFFERSIZE;

        qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        qc->tf.command = ATA_CMD_PACKET;

        qc->tf.protocol = ATA_PROT_ATAPI;
        qc->tf.lbam = (8 * 1024) & 0xff;
        qc->tf.lbah = (8 * 1024) >> 8;
        qc->nbytes = SCSI_SENSE_BUFFERSIZE;

        qc->waiting = &wait;
        qc->complete_fn = ata_qc_complete_noop;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        rc = ata_qc_issue(qc);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        if (rc)
                ata_port_disable(ap);
        else
                wait_for_completion(&wait);

        DPRINTK("EXIT\n");
}

/**
 *      ata_qc_timeout - Handle timeout of queued command
 *      @qc: Command that timed out
 *
 *      Some part of the kernel (currently, only the SCSI layer)
 *      has noticed that the active command on port @ap has not
 *      completed after a specified length of time.  Handle this
 *      condition by disabling DMA (if necessary) and completing
 *      transactions, with error if necessary.
 *
 *      This also handles the case of the "lost interrupt", where
 *      for some reason (possibly hardware bug, possibly driver bug)
 *      an interrupt was not delivered to the driver, even though the
 *      transaction completed successfully.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 */

static void ata_qc_timeout(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct ata_host_set *host_set = ap->host_set;
        struct ata_device *dev = qc->dev;
        u8 host_stat = 0, drv_stat;
        unsigned long flags;

        DPRINTK("ENTER\n");

        /* FIXME: doesn't this conflict with timeout handling? */
        if (qc->dev->class == ATA_DEV_ATAPI && qc->scsicmd) {
                struct scsi_cmnd *cmd = qc->scsicmd;

                if (!(cmd->eh_eflags & SCSI_EH_CANCEL_CMD)) {

                        /* finish completing original command */
                        spin_lock_irqsave(&host_set->lock, flags);
                        __ata_qc_complete(qc);
                        spin_unlock_irqrestore(&host_set->lock, flags);

                        atapi_request_sense(ap, dev, cmd);

                        cmd->result = (CHECK_CONDITION << 1) | (DID_OK << 16);
                        scsi_finish_command(cmd);

                        goto out;
                }
        }

        spin_lock_irqsave(&host_set->lock, flags);

        /* hack alert!  We cannot use the supplied completion
         * function from inside the ->eh_strategy_handler() thread.
         * libata is the only user of ->eh_strategy_handler() in
         * any kernel, so the default scsi_done() assumes it is
         * not being called from the SCSI EH.
         */
        qc->scsidone = scsi_finish_command;

        switch (qc->tf.protocol) {

        case ATA_PROT_DMA:
        case ATA_PROT_ATAPI_DMA:
                host_stat = ap->ops->bmdma_status(ap);

                /* before we do anything else, clear DMA-Start bit */
                ap->ops->bmdma_stop(qc);

                /* fall through */

        default:
                ata_altstatus(ap);
                drv_stat = ata_chk_status(ap);

                /* ack bmdma irq events */
                ap->ops->irq_clear(ap);

                printk(KERN_ERR "ata%u: command 0x%x timeout, stat 0x%x host_stat 0x%x\n",
                       ap->id, qc->tf.command, drv_stat, host_stat);

                /* complete taskfile transaction */
                ata_qc_complete(qc, drv_stat);
                break;
        }

        spin_unlock_irqrestore(&host_set->lock, flags);

out:
        DPRINTK("EXIT\n");
}

/**
 *      ata_eng_timeout - Handle timeout of queued command
 *      @ap: Port on which timed-out command is active
 *
 *      Some part of the kernel (currently, only the SCSI layer)
 *      has noticed that the active command on port @ap has not
 *      completed after a specified length of time.  Handle this
 *      condition by disabling DMA (if necessary) and completing
 *      transactions, with error if necessary.
 *
 *      This also handles the case of the "lost interrupt", where
 *      for some reason (possibly hardware bug, possibly driver bug)
 *      an interrupt was not delivered to the driver, even though the
 *      transaction completed successfully.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 */

void ata_eng_timeout(struct ata_port *ap)
{
        struct ata_queued_cmd *qc;

        DPRINTK("ENTER\n");

        qc = ata_qc_from_tag(ap, ap->active_tag);
        if (!qc) {
                printk(KERN_ERR "ata%u: BUG: timeout without command\n",
                       ap->id);
                goto out;
        }

        ata_qc_timeout(qc);

out:
        DPRINTK("EXIT\n");
}

/**
 *      ata_qc_new - Request an available ATA command, for queueing
 *      @ap: Port associated with device @dev
 *      @dev: Device from whom we request an available command structure
 *
 *      LOCKING:
 *      None.
 */

static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
{
        struct ata_queued_cmd *qc = NULL;
        unsigned int i;

        for (i = 0; i < ATA_MAX_QUEUE; i++)
                if (!test_and_set_bit(i, &ap->qactive)) {
                        qc = ata_qc_from_tag(ap, i);
                        break;
                }

        if (qc)
                qc->tag = i;

        return qc;
}

/**
 *      ata_qc_new_init - Request an available ATA command, and initialize it
 *      @ap: Port associated with device @dev
 *      @dev: Device from whom we request an available command structure
 *
 *      LOCKING:
 *      None.
 */

struct ata_queued_cmd *ata_qc_new_init(struct ata_port *ap,
                                      struct ata_device *dev)
{
        struct ata_queued_cmd *qc;

        qc = ata_qc_new(ap);
        if (qc) {
                qc->sg = NULL;
                qc->flags = 0;
                qc->scsicmd = NULL;
                qc->ap = ap;
                qc->dev = dev;
                qc->cursect = qc->cursg = qc->cursg_ofs = 0;
                qc->nsect = 0;
                qc->nbytes = qc->curbytes = 0;

                ata_tf_init(ap, &qc->tf, dev->devno);

                if (dev->flags & ATA_DFLAG_LBA) {
                        qc->tf.flags |= ATA_TFLAG_LBA;

                        if (dev->flags & ATA_DFLAG_LBA48)
                                qc->tf.flags |= ATA_TFLAG_LBA48;
                }
        }

        return qc;
}

static int ata_qc_complete_noop(struct ata_queued_cmd *qc, u8 drv_stat)
{
        return 0;
}

static void __ata_qc_complete(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        unsigned int tag, do_clear = 0;

        qc->flags = 0;
        tag = qc->tag;
        if (likely(ata_tag_valid(tag))) {
                if (tag == ap->active_tag)
                        ap->active_tag = ATA_TAG_POISON;
                qc->tag = ATA_TAG_POISON;
                do_clear = 1;
        }

        if (qc->waiting) {
                struct completion *waiting = qc->waiting;
                qc->waiting = NULL;
                complete(waiting);
        }

        if (likely(do_clear))
                clear_bit(tag, &ap->qactive);
}

/**
 *      ata_qc_free - free unused ata_queued_cmd
 *      @qc: Command to complete
 *
 *      Designed to free unused ata_queued_cmd object
 *      in case something prevents using it.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 */
void ata_qc_free(struct ata_queued_cmd *qc)
{
        assert(qc != NULL);     /* ata_qc_from_tag _might_ return NULL */
        assert(qc->waiting == NULL);    /* nothing should be waiting */

        __ata_qc_complete(qc);
}

/**
 *      ata_qc_complete - Complete an active ATA command
 *      @qc: Command to complete
 *      @drv_stat: ATA Status register contents
 *
 *      Indicate to the mid and upper layers that an ATA
 *      command has completed, with either an ok or not-ok status.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 */

void ata_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
{
        int rc;

        assert(qc != NULL);     /* ata_qc_from_tag _might_ return NULL */
        assert(qc->flags & ATA_QCFLAG_ACTIVE);

        if (likely(qc->flags & ATA_QCFLAG_DMAMAP))
                ata_sg_clean(qc);

        /* atapi: mark qc as inactive to prevent the interrupt handler
         * from completing the command twice later, before the error handler
         * is called. (when rc != 0 and atapi request sense is needed)
         */
        qc->flags &= ~ATA_QCFLAG_ACTIVE;

        /* call completion callback */
        rc = qc->complete_fn(qc, drv_stat);

        /* if callback indicates not to complete command (non-zero),
         * return immediately
         */
        if (rc != 0)
                return;

        __ata_qc_complete(qc);

        VPRINTK("EXIT\n");
}

static inline int ata_should_dma_map(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;

        switch (qc->tf.protocol) {
        case ATA_PROT_DMA:
        case ATA_PROT_ATAPI_DMA:
                return 1;

        case ATA_PROT_ATAPI:
        case ATA_PROT_PIO:
        case ATA_PROT_PIO_MULT:
                if (ap->flags & ATA_FLAG_PIO_DMA)
                        return 1;

                /* fall through */

        default:
                return 0;
        }

        /* never reached */
}

/**
 *      ata_qc_issue - issue taskfile to device
 *      @qc: command to issue to device
 *
 *      Prepare an ATA command to submission to device.
 *      This includes mapping the data into a DMA-able
 *      area, filling in the S/G table, and finally
 *      writing the taskfile to hardware, starting the command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, negative on error.
 */

int ata_qc_issue(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;

        if (ata_should_dma_map(qc)) {
                if (qc->flags & ATA_QCFLAG_SG) {
                        if (ata_sg_setup(qc))
                                goto err_out;
                } else if (qc->flags & ATA_QCFLAG_SINGLE) {
                        if (ata_sg_setup_one(qc))
                                goto err_out;
                }
        } else {
                qc->flags &= ~ATA_QCFLAG_DMAMAP;
        }

        ap->ops->qc_prep(qc);

        qc->ap->active_tag = qc->tag;
        qc->flags |= ATA_QCFLAG_ACTIVE;

        return ap->ops->qc_issue(qc);

err_out:
        return -1;
}


/**
 *      ata_qc_issue_prot - issue taskfile to device in proto-dependent manner
 *      @qc: command to issue to device
 *
 *      Using various libata functions and hooks, this function
 *      starts an ATA command.  ATA commands are grouped into
 *      classes called "protocols", and issuing each type of protocol
 *      is slightly different.
 *
 *      May be used as the qc_issue() entry in ata_port_operations.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, negative on error.
 */

int ata_qc_issue_prot(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;

        ata_dev_select(ap, qc->dev->devno, 1, 0);

        switch (qc->tf.protocol) {
        case ATA_PROT_NODATA:
                ata_tf_to_host_nolock(ap, &qc->tf);
                break;

        case ATA_PROT_DMA:
                ap->ops->tf_load(ap, &qc->tf);   /* load tf registers */
                ap->ops->bmdma_setup(qc);           /* set up bmdma */
                ap->ops->bmdma_start(qc);           /* initiate bmdma */
                break;

        case ATA_PROT_PIO: /* load tf registers, initiate polling pio */
            &n