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

/*
   libata-core.c - helper library for ATA

   Copyright 2003-2004 Red Hat, Inc.  All rights reserved.
   Copyright 2003-2004 Jeff Garzik

   The contents of this file are subject to the Open
   Software License version 1.1 that can be found at
   http://www.opensource.org/licenses/osl-1.1.txt and is included herein
   by reference.

   Alternatively, the contents of this file may be used under the terms
   of the GNU General Public License version 2 (the "GPL") as distributed
   in the kernel source COPYING file, in which case the provisions of
   the GPL are applicable instead of the above.  If you wish to allow
   the use of your version of this file only under the terms of the
   GPL and not to allow others to use your version of this file under
   the OSL, indicate your decision by deleting the provisions above and
   replace them with the notice and other provisions required by the GPL.
   If you do not delete the provisions above, a recipient may use your
   version of this file under either the OSL or the GPL.

 */

#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_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 i;
        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 LBA and DMA support (bits 8 & 9 of word 49) */
        if (!ata_id_has_dma(dev->id) || !ata_id_has_lba(dev->id)) {
                printk(KERN_DEBUG "ata%u: no dma/lba\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;

                tmp = dev->id[ATA_ID_MAJOR_VER];
                for (i = 14; i >= 1; i--)
                        if (tmp & (1 << i))
                                break;

                /* we require at least ATA-3 */
                if (i < 3) {
                        printk(KERN_DEBUG "ata%u: no ATA-3\n", ap->id);
                        goto err_out_nosup;
                }

                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);
                }

                ap->host->max_cmd_len = 16;

                /* print device info to dmesg */
                printk(KERN_INFO "ata%u: dev %u ATA, max %s, %Lu sectors:%s\n",
                       ap->id, device,
                       ata_mode_string(xfer_modes),
                       (unsigned long long)dev->n_sectors,
                       dev->flags & ATA_DFLAG_LBA48 ? " lba48" : "");
        }

        /* 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_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)
 */



/**
 *      ata_sg_init_one - Prepare a one-entry scatter-gather list.
 *      @qc:  Queued command
 *      @buf:  transfer buffer
 *      @buflen:  length of buf
 *
 *      Builds a single-entry scatter-gather list to initiate a
 *      transfer utilizing the specified buffer.
 *
 *      LOCKING:
 */
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)
 */


/**
 *      ata_sg_init - Assign a scatter gather list to a queued command
 *      @qc:  Queued command
 *      @sg:  Scatter-gather list
 *      @n_elem:  length of sg list
 *
 *      Attaches a scatter-gather list to a queued command.
 *
 *      LOCKING:
 */

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_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 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.
         */
        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_irq_on(ap);

        ata_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_irq_on(ap);

                        ata_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_irq_on(ap);

        ata_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_device *dev = qc->dev;
        u8 host_stat = 0, drv_stat;

        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 */
                        __ata_qc_complete(qc);

                        atapi_request_sense(ap, dev, cmd);

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

                        goto out;
                }
        }

        /* 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(ap);

                /* 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;
        }
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_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);

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

        /* 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 */
                ata_qc_set_polling(qc);
                ata_tf_to_host_nolock(ap, &qc->tf);
                ap->pio_task_state = PIO_ST;
                queue_work(ata_wq, &ap->pio_task);
                break;

        case ATA_PROT_ATAPI:
                ata_qc_set_polling(qc);
                ata_tf_to_host_nolock(ap, &qc->tf);
                queue_work(ata_wq, &ap->packet_task);
                break;

        case ATA_PROT_ATAPI_NODATA:
                ata_tf_to_host_nolock(ap, &qc->tf);
                queue_work(ata_wq, &ap->packet_task);
                break;

        case ATA_PROT_ATAPI_DMA:
                ap->ops->tf_load(ap, &qc->tf);   /* load tf registers */
                ap->ops->bmdma_setup(qc);           /* set up bmdma */
                queue_work(ata_wq, &ap->packet_task);
                break;

        default:
                WARN_ON(1);
                return -1;
        }

        return 0;
}

/**
 *      ata_bmdma_setup_mmio - Set up PCI IDE BMDMA transaction
 *      @qc: Info associated with this ATA transaction.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_bmdma_setup_mmio (struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        unsigned int rw = (qc->tf.flags & ATA_TFLAG_WRITE);
        u8 dmactl;
        void __iomem *mmio = (void __iomem *) ap->ioaddr.bmdma_addr;

        /* load PRD table addr. */
        mb();   /* make sure PRD table writes are visible to controller */
        writel(ap->prd_dma, mmio + ATA_DMA_TABLE_OFS);

        /* specify data direction, triple-check start bit is clear */
        dmactl = readb(mmio + ATA_DMA_CMD);
        dmactl &= ~(ATA_DMA_WR | ATA_DMA_START);
        if (!rw)
                dmactl |= ATA_DMA_WR;
        writeb(dmactl, mmio + ATA_DMA_CMD);

        /* issue r/w command */
        ap->ops->exec_command(ap, &qc->tf);
}

/**
 *      ata_bmdma_start - Start a PCI IDE BMDMA transaction
 *      @qc: Info associated with this ATA transaction.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_bmdma_start_mmio (struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        void __iomem *mmio = (void __iomem *) ap->ioaddr.bmdma_addr;
        u8 dmactl;

        /* start host DMA transaction */
        dmactl = readb(mmio + ATA_DMA_CMD);
        writeb(dmactl | ATA_DMA_START, mmio + ATA_DMA_CMD);

        /* Strictly, one may wish to issue a readb() here, to
         * flush the mmio write.  However, control also passes
         * to the hardware at this point, and it will interrupt
         * us when we are to resume control.  So, in effect,
         * we don't care when the mmio write flushes.
         * Further, a read of the DMA status register _immediately_
         * following the write may not be what certain flaky hardware
         * is expected, so I think it is best to not add a readb()
         * without first all the MMIO ATA cards/mobos.
         * Or maybe I'm just being paranoid.
         */
}

/**
 *      ata_bmdma_setup_pio - Set up PCI IDE BMDMA transaction (PIO)
 *      @qc: Info associated with this ATA transaction.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_bmdma_setup_pio (struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        unsigned int rw = (qc->tf.flags & ATA_TFLAG_WRITE);
        u8 dmactl;

        /* load PRD table addr. */
        outl(ap->prd_dma, ap->ioaddr.bmdma_addr + ATA_DMA_TABLE_OFS);

        /* specify data direction, triple-check start bit is clear */
        dmactl = inb(ap->ioaddr.bmdma_addr + ATA_DMA_CMD);
        dmactl &= ~(ATA_DMA_WR | ATA_DMA_START);
        if (!rw)
                dmactl |= ATA_DMA_WR;
        outb(dmactl, ap->ioaddr.bmdma_addr + ATA_DMA_CMD);