Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
[linux-3.10.git] / drivers / input / touchscreen / ads7846.c
index 46d1fec..58934a4 100644 (file)
@@ -2,6 +2,8 @@
  * ADS7846 based touchscreen and sensor driver
  *
  * Copyright (c) 2005 David Brownell
+ * Copyright (c) 2006 Nokia Corporation
+ * Various changes: Imre Deak <imre.deak@nokia.com>
  *
  * Using code from:
  *  - corgi_ts.c
@@ -15,8 +17,9 @@
  *  it under the terms of the GNU General Public License version 2 as
  *  published by the Free Software Foundation.
  */
-#include <linux/device.h>
+#include <linux/hwmon.h>
 #include <linux/init.h>
+#include <linux/err.h>
 #include <linux/delay.h>
 #include <linux/input.h>
 #include <linux/interrupt.h>
 
 
 /*
- * This code has been lightly tested on an ads7846.
- * Support for ads7843 and ads7845 has only been stubbed in.
+ * This code has been heavily tested on a Nokia 770, and lightly
+ * tested on other ads7846 devices (OSK/Mistral, Lubbock).
+ * TSC2046 is just newer ads7846 silicon.
+ * Support for ads7843 tested on Atmel at91sam926x-EK.
+ * Support for ads7845 has only been stubbed in.
  *
- * Not yet done:  investigate the values reported.  Are x/y/pressure
- * event values sane enough for X11?  How accurate are the temperature
- * and voltage readings?  (System-specific calibration should support
- * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
+ * IRQ handling needs a workaround because of a shortcoming in handling
+ * edge triggered IRQs on some platforms like the OMAP1/2. These
+ * platforms don't handle the ARM lazy IRQ disabling properly, thus we
+ * have to maintain our own SW IRQ disabled status. This should be
+ * removed as soon as the affected platform's IRQ handling is fixed.
  *
  * app note sbaa036 talks in more detail about accurate sampling...
  * that ought to help in situations like LCDs inducing noise (which
  * can also be helped by using synch signals) and more generally.
+ * This driver tries to utilize the measures described in the app
+ * note. The strength of filtering can be set in the board-* specific
+ * files.
  */
 
-#define        TS_POLL_PERIOD  msecs_to_jiffies(10)
+#define TS_POLL_DELAY  (1 * 1000000)   /* ns delay before the first sample */
+#define TS_POLL_PERIOD (5 * 1000000)   /* ns delay between samples */
 
 /* this driver doesn't aim at the peak continuous sample rate */
 #define        SAMPLE_BITS     (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
@@ -56,11 +67,12 @@ struct ts_event {
        /* For portability, we can't read 12 bit values using SPI (which
         * would make the controller deliver them as native byteorder u16
         * with msbs zeroed).  Instead, we read them as two 8-bit values,
-        * which need byteswapping then range adjustment.
+        * *** WHICH NEED BYTESWAPPING *** and range adjustment.
         */
-       __be16 x;
-       __be16 y;
-       __be16 z1, z2;
+       u16     x;
+       u16     y;
+       u16     z1, z2;
+       int     ignore;
 };
 
 struct ads7846 {
@@ -68,22 +80,48 @@ struct ads7846 {
        char                    phys[32];
 
        struct spi_device       *spi;
+
+#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)
+       struct attribute_group  *attr_group;
+       struct device           *hwmon;
+#endif
+
        u16                     model;
        u16                     vref_delay_usecs;
        u16                     x_plate_ohms;
+       u16                     pressure_max;
 
-       u8                      read_x, read_y, read_z1, read_z2;
+       u8                      read_x, read_y, read_z1, read_z2, pwrdown;
+       u16                     dummy;          /* for the pwrdown read */
        struct ts_event         tc;
 
-       struct spi_transfer     xfer[8];
-       struct spi_message      msg;
+       struct spi_transfer     xfer[18];
+       struct spi_message      msg[5];
+       struct spi_message      *last_msg;
+       int                     msg_idx;
+       int                     read_cnt;
+       int                     read_rep;
+       int                     last_read;
+
+       u16                     debounce_max;
+       u16                     debounce_tol;
+       u16                     debounce_rep;
+
+       u16                     penirq_recheck_delay_usecs;
 
        spinlock_t              lock;
-       struct timer_list       timer;          /* P: lock */
+       struct hrtimer          timer;
        unsigned                pendown:1;      /* P: lock */
        unsigned                pending:1;      /* P: lock */
 // FIXME remove "irq_disabled"
        unsigned                irq_disabled:1; /* P: lock */
+       unsigned                disabled:1;
+       unsigned                is_suspended:1;
+
+       int                     (*filter)(void *data, int data_idx, int *val);
+       void                    *filter_data;
+       void                    (*filter_cleanup)(void *data);
+       int                     (*get_pendown_state)(void);
 };
 
 /* leave chip selected when we're done, for quicker re-select? */
@@ -119,13 +157,16 @@ struct ads7846 {
 #define        MAX_12BIT       ((1<<12)-1)
 
 /* leave ADC powered up (disables penirq) between differential samples */
-#define        READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
-       | ADS_12_BIT | ADS_DFR)
+#define        READ_12BIT_DFR(x, adc, vref) (ADS_START | ADS_A2A1A0_d_ ## x \
+       | ADS_12_BIT | ADS_DFR | \
+       (adc ? ADS_PD10_ADC_ON : 0) | (vref ? ADS_PD10_REF_ON : 0))
 
-#define        READ_Y  (READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON)
-#define        READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
-#define        READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
-#define        READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_PDOWN)   /* LAST */
+#define        READ_Y(vref)    (READ_12BIT_DFR(y,  1, vref))
+#define        READ_Z1(vref)   (READ_12BIT_DFR(z1, 1, vref))
+#define        READ_Z2(vref)   (READ_12BIT_DFR(z2, 1, vref))
+
+#define        READ_X(vref)    (READ_12BIT_DFR(x,  1, vref))
+#define        PWRDOWN         (READ_12BIT_DFR(y,  0, 0))      /* LAST */
 
 /* single-ended samples need to first power up reference voltage;
  * we leave both ADC and VREF powered
@@ -133,14 +174,19 @@ struct ads7846 {
 #define        READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
        | ADS_12_BIT | ADS_SER)
 
-#define        REF_ON  (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
-#define        REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
+#define        REF_ON  (READ_12BIT_DFR(x, 1, 1))
+#define        REF_OFF (READ_12BIT_DFR(y, 0, 0))
 
 /*--------------------------------------------------------------------------*/
 
 /*
  * Non-touchscreen sensors only use single-ended conversions.
+ * The range is GND..vREF. The ads7843 and ads7835 must use external vREF;
+ * ads7846 lets that pin be unconnected, to use internal vREF.
  */
+static unsigned vREF_mV;
+module_param(vREF_mV, uint, 0);
+MODULE_PARM_DESC(vREF_mV, "external vREF voltage, in milliVolts");
 
 struct ser_req {
        u8                      ref_on;
@@ -152,86 +198,306 @@ struct ser_req {
        struct spi_transfer     xfer[6];
 };
 
+static void ads7846_enable(struct ads7846 *ts);
+static void ads7846_disable(struct ads7846 *ts);
+
+static int device_suspended(struct device *dev)
+{
+       struct ads7846 *ts = dev_get_drvdata(dev);
+       return ts->is_suspended || ts->disabled;
+}
+
 static int ads7846_read12_ser(struct device *dev, unsigned command)
 {
        struct spi_device       *spi = to_spi_device(dev);
        struct ads7846          *ts = dev_get_drvdata(dev);
-       struct ser_req          *req = kzalloc(sizeof *req, SLAB_KERNEL);
+       struct ser_req          *req = kzalloc(sizeof *req, GFP_KERNEL);
        int                     status;
        int                     sample;
-       int                     i;
+       int                     use_internal;
 
        if (!req)
                return -ENOMEM;
 
-       INIT_LIST_HEAD(&req->msg.transfers);
+       spi_message_init(&req->msg);
 
-       /* activate reference, so it has time to settle; */
-       req->ref_on = REF_ON;
-       req->xfer[0].tx_buf = &req->ref_on;
-       req->xfer[0].len = 1;
-       req->xfer[1].rx_buf = &req->scratch;
-       req->xfer[1].len = 2;
+       /* FIXME boards with ads7846 might use external vref instead ... */
+       use_internal = (ts->model == 7846);
 
-       /*
-        * for external VREF, 0 usec (and assume it's always on);
-        * for 1uF, use 800 usec;
-        * no cap, 100 usec.
-        */
-       req->xfer[1].delay_usecs = ts->vref_delay_usecs;
+       /* maybe turn on internal vREF, and let it settle */
+       if (use_internal) {
+               req->ref_on = REF_ON;
+               req->xfer[0].tx_buf = &req->ref_on;
+               req->xfer[0].len = 1;
+               spi_message_add_tail(&req->xfer[0], &req->msg);
+
+               req->xfer[1].rx_buf = &req->scratch;
+               req->xfer[1].len = 2;
+
+               /* for 1uF, settle for 800 usec; no cap, 100 usec.  */
+               req->xfer[1].delay_usecs = ts->vref_delay_usecs;
+               spi_message_add_tail(&req->xfer[1], &req->msg);
+       }
 
        /* take sample */
        req->command = (u8) command;
        req->xfer[2].tx_buf = &req->command;
        req->xfer[2].len = 1;
+       spi_message_add_tail(&req->xfer[2], &req->msg);
+
        req->xfer[3].rx_buf = &req->sample;
        req->xfer[3].len = 2;
+       spi_message_add_tail(&req->xfer[3], &req->msg);
 
        /* REVISIT:  take a few more samples, and compare ... */
 
-       /* turn off reference */
-       req->ref_off = REF_OFF;
+       /* converter in low power mode & enable PENIRQ */
+       req->ref_off = PWRDOWN;
        req->xfer[4].tx_buf = &req->ref_off;
        req->xfer[4].len = 1;
+       spi_message_add_tail(&req->xfer[4], &req->msg);
+
        req->xfer[5].rx_buf = &req->scratch;
        req->xfer[5].len = 2;
-
        CS_CHANGE(req->xfer[5]);
+       spi_message_add_tail(&req->xfer[5], &req->msg);
 
-       /* group all the transfers together, so we can't interfere with
-        * reading touchscreen state; disable penirq while sampling
-        */
-       for (i = 0; i < 6; i++)
-               spi_message_add_tail(&req->xfer[i], &req->msg);
-
+       ts->irq_disabled = 1;
        disable_irq(spi->irq);
        status = spi_sync(spi, &req->msg);
+       ts->irq_disabled = 0;
        enable_irq(spi->irq);
 
-       if (req->msg.status)
-               status = req->msg.status;
-       sample = be16_to_cpu(req->sample);
-       sample = sample >> 4;
-       kfree(req);
+       if (status == 0) {
+               /* on-wire is a must-ignore bit, a BE12 value, then padding */
+               sample = be16_to_cpu(req->sample);
+               sample = sample >> 3;
+               sample &= 0x0fff;
+       }
 
+       kfree(req);
        return status ? status : sample;
 }
 
-#define SHOW(name) static ssize_t \
+#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)
+
+#define SHOW(name, var, adjust) static ssize_t \
 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 { \
+       struct ads7846 *ts = dev_get_drvdata(dev); \
        ssize_t v = ads7846_read12_ser(dev, \
-                       READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
+                       READ_12BIT_SER(var) | ADS_PD10_ALL_ON); \
        if (v < 0) \
                return v; \
-       return sprintf(buf, "%u\n", (unsigned) v); \
+       return sprintf(buf, "%u\n", adjust(ts, v)); \
 } \
 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
 
-SHOW(temp0)
-SHOW(temp1)
-SHOW(vaux)
-SHOW(vbatt)
+
+/* Sysfs conventions report temperatures in millidegrees Celcius.
+ * ADS7846 could use the low-accuracy two-sample scheme, but can't do the high
+ * accuracy scheme without calibration data.  For now we won't try either;
+ * userspace sees raw sensor values, and must scale/calibrate appropriately.
+ */
+static inline unsigned null_adjust(struct ads7846 *ts, ssize_t v)
+{
+       return v;
+}
+
+SHOW(temp0, temp0, null_adjust)                /* temp1_input */
+SHOW(temp1, temp1, null_adjust)                /* temp2_input */
+
+
+/* sysfs conventions report voltages in millivolts.  We can convert voltages
+ * if we know vREF.  userspace may need to scale vAUX to match the board's
+ * external resistors; we assume that vBATT only uses the internal ones.
+ */
+static inline unsigned vaux_adjust(struct ads7846 *ts, ssize_t v)
+{
+       unsigned retval = v;
+
+       /* external resistors may scale vAUX into 0..vREF */
+       retval *= vREF_mV;
+       retval = retval >> 12;
+       return retval;
+}
+
+static inline unsigned vbatt_adjust(struct ads7846 *ts, ssize_t v)
+{
+       unsigned retval = vaux_adjust(ts, v);
+
+       /* ads7846 has a resistor ladder to scale this signal down */
+       if (ts->model == 7846)
+               retval *= 4;
+       return retval;
+}
+
+SHOW(in0_input, vaux, vaux_adjust)
+SHOW(in1_input, vbatt, vbatt_adjust)
+
+
+static struct attribute *ads7846_attributes[] = {
+       &dev_attr_temp0.attr,
+       &dev_attr_temp1.attr,
+       &dev_attr_in0_input.attr,
+       &dev_attr_in1_input.attr,
+       NULL,
+};
+
+static struct attribute_group ads7846_attr_group = {
+       .attrs = ads7846_attributes,
+};
+
+static struct attribute *ads7843_attributes[] = {
+       &dev_attr_in0_input.attr,
+       &dev_attr_in1_input.attr,
+       NULL,
+};
+
+static struct attribute_group ads7843_attr_group = {
+       .attrs = ads7843_attributes,
+};
+
+static struct attribute *ads7845_attributes[] = {
+       &dev_attr_in0_input.attr,
+       NULL,
+};
+
+static struct attribute_group ads7845_attr_group = {
+       .attrs = ads7845_attributes,
+};
+
+static int ads784x_hwmon_register(struct spi_device *spi, struct ads7846 *ts)
+{
+       struct device *hwmon;
+       int err;
+
+       /* hwmon sensors need a reference voltage */
+       switch (ts->model) {
+       case 7846:
+               if (!vREF_mV) {
+                       dev_dbg(&spi->dev, "assuming 2.5V internal vREF\n");
+                       vREF_mV = 2500;
+               }
+               break;
+       case 7845:
+       case 7843:
+               if (!vREF_mV) {
+                       dev_warn(&spi->dev,
+                               "external vREF for ADS%d not specified\n",
+                               ts->model);
+                       return 0;
+               }
+               break;
+       }
+
+       /* different chips have different sensor groups */
+       switch (ts->model) {
+       case 7846:
+               ts->attr_group = &ads7846_attr_group;
+               break;
+       case 7845:
+               ts->attr_group = &ads7845_attr_group;
+               break;
+       case 7843:
+               ts->attr_group = &ads7843_attr_group;
+               break;
+       default:
+               dev_dbg(&spi->dev, "ADS%d not recognized\n", ts->model);
+               return 0;
+       }
+
+       err = sysfs_create_group(&spi->dev.kobj, ts->attr_group);
+       if (err)
+               return err;
+
+       hwmon = hwmon_device_register(&spi->dev);
+       if (IS_ERR(hwmon)) {
+               sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
+               return PTR_ERR(hwmon);
+       }
+
+       ts->hwmon = hwmon;
+       return 0;
+}
+
+static void ads784x_hwmon_unregister(struct spi_device *spi,
+                                    struct ads7846 *ts)
+{
+       if (ts->hwmon) {
+               sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
+               hwmon_device_unregister(ts->hwmon);
+       }
+}
+
+#else
+static inline int ads784x_hwmon_register(struct spi_device *spi,
+                                        struct ads7846 *ts)
+{
+       return 0;
+}
+
+static inline void ads784x_hwmon_unregister(struct spi_device *spi,
+                                           struct ads7846 *ts)
+{
+}
+#endif
+
+static int is_pen_down(struct device *dev)
+{
+       struct ads7846  *ts = dev_get_drvdata(dev);
+
+       return ts->pendown;
+}
+
+static ssize_t ads7846_pen_down_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "%u\n", is_pen_down(dev));
+}
+
+static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);
+
+static ssize_t ads7846_disable_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+       struct ads7846  *ts = dev_get_drvdata(dev);
+
+       return sprintf(buf, "%u\n", ts->disabled);
+}
+
+static ssize_t ads7846_disable_store(struct device *dev,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t count)
+{
+       struct ads7846 *ts = dev_get_drvdata(dev);
+       char *endp;
+       int i;
+
+       i = simple_strtoul(buf, &endp, 10);
+       spin_lock_irq(&ts->lock);
+
+       if (i)
+               ads7846_disable(ts);
+       else
+               ads7846_enable(ts);
+
+       spin_unlock_irq(&ts->lock);
+
+       return count;
+}
+
+static DEVICE_ATTR(disable, 0664, ads7846_disable_show, ads7846_disable_store);
+
+static struct attribute *ads784x_attributes[] = {
+       &dev_attr_pen_down.attr,
+       &dev_attr_disable.attr,
+       NULL,
+};
+
+static struct attribute_group ads784x_attr_group = {
+       .attrs = ads784x_attributes,
+};
 
 /*--------------------------------------------------------------------------*/
 
@@ -246,25 +512,22 @@ SHOW(vbatt)
 static void ads7846_rx(void *ads)
 {
        struct ads7846          *ts = ads;
-       struct input_dev        *input_dev = ts->input;
        unsigned                Rt;
-       unsigned                sync = 0;
        u16                     x, y, z1, z2;
-       unsigned long           flags;
 
-       /* adjust:  12 bit samples (left aligned), built from
-        * two 8 bit values writen msb-first.
+       /* ads7846_rx_val() did in-place conversion (including byteswap) from
+        * on-the-wire format as part of debouncing to get stable readings.
         */
-       x = be16_to_cpu(ts->tc.x) >> 4;
-       y = be16_to_cpu(ts->tc.y) >> 4;
-       z1 = be16_to_cpu(ts->tc.z1) >> 4;
-       z2 = be16_to_cpu(ts->tc.z2) >> 4;
+       x = ts->tc.x;
+       y = ts->tc.y;
+       z1 = ts->tc.z1;
+       z2 = ts->tc.z2;
 
        /* range filtering */
        if (x == MAX_12BIT)
                x = 0;
 
-       if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
+       if (likely(x && z1)) {
                /* compute touch pressure resistance using equation #2 */
                Rt = z2;
                Rt -= z1;
@@ -275,113 +538,237 @@ static void ads7846_rx(void *ads)
        } else
                Rt = 0;
 
-       /* NOTE:  "pendown" is inferred from pressure; we don't rely on
-        * being able to check nPENIRQ status, or "friendly" trigger modes
-        * (both-edges is much better than just-falling or low-level).
-        *
-        * REVISIT:  some boards may require reading nPENIRQ; it's
-        * needed on 7843.  and 7845 reads pressure differently...
-        *
-        * REVISIT:  the touchscreen might not be connected; this code
-        * won't notice that, even if nPENIRQ never fires ...
+       if (ts->model == 7843)
+               Rt = ts->pressure_max / 2;
+
+       /* Sample found inconsistent by debouncing or pressure is beyond
+        * the maximum. Don't report it to user space, repeat at least
+        * once more the measurement
         */
-       if (!ts->pendown && Rt != 0) {
-               input_report_key(input_dev, BTN_TOUCH, 1);
-               sync = 1;
-       } else if (ts->pendown && Rt == 0) {
-               input_report_key(input_dev, BTN_TOUCH, 0);
-               sync = 1;
+       if (ts->tc.ignore || Rt > ts->pressure_max) {
+#ifdef VERBOSE
+               pr_debug("%s: ignored %d pressure %d\n",
+                       ts->spi->dev.bus_id, ts->tc.ignore, Rt);
+#endif
+               hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
+                             HRTIMER_MODE_REL);
+               return;
        }
 
-       if (Rt) {
-               input_report_abs(input_dev, ABS_X, x);
-               input_report_abs(input_dev, ABS_Y, y);
-               input_report_abs(input_dev, ABS_PRESSURE, Rt);
-               sync = 1;
+       /* Maybe check the pendown state before reporting. This discards
+        * false readings when the pen is lifted.
+        */
+       if (ts->penirq_recheck_delay_usecs) {
+               udelay(ts->penirq_recheck_delay_usecs);
+               if (!ts->get_pendown_state())
+                       Rt = 0;
        }
-       if (sync)
-               input_sync(input_dev);
 
-#ifdef VERBOSE
-       if (Rt || ts->pendown)
-               pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
-                       x, y, Rt, Rt ? "" : " UP");
+       /* NOTE: We can't rely on the pressure to determine the pen down
+        * state, even this controller has a pressure sensor.  The pressure
+        * value can fluctuate for quite a while after lifting the pen and
+        * in some cases may not even settle at the expected value.
+        *
+        * The only safe way to check for the pen up condition is in the
+        * timer by reading the pen signal state (it's a GPIO _and_ IRQ).
+        */
+       if (Rt) {
+               struct input_dev *input = ts->input;
+
+               if (!ts->pendown) {
+                       input_report_key(input, BTN_TOUCH, 1);
+                       ts->pendown = 1;
+#ifdef VERBOSE
+                       dev_dbg(&ts->spi->dev, "DOWN\n");
 #endif
+               }
+               input_report_abs(input, ABS_X, x);
+               input_report_abs(input, ABS_Y, y);
+               input_report_abs(input, ABS_PRESSURE, Rt);
 
-       /* don't retrigger while we're suspended */
-       spin_lock_irqsave(&ts->lock, flags);
+               input_sync(input);
+#ifdef VERBOSE
+               dev_dbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
+#endif
+       }
+
+       hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
+                       HRTIMER_MODE_REL);
+}
+
+static int ads7846_debounce(void *ads, int data_idx, int *val)
+{
+       struct ads7846          *ts = ads;
+
+       if (!ts->read_cnt || (abs(ts->last_read - *val) > ts->debounce_tol)) {
+               /* Start over collecting consistent readings. */
+               ts->read_rep = 0;
+               /* Repeat it, if this was the first read or the read
+                * wasn't consistent enough. */
+               if (ts->read_cnt < ts->debounce_max) {
+                       ts->last_read = *val;
+                       ts->read_cnt++;
+                       return ADS7846_FILTER_REPEAT;
+               } else {
+                       /* Maximum number of debouncing reached and still
+                        * not enough number of consistent readings. Abort
+                        * the whole sample, repeat it in the next sampling
+                        * period.
+                        */
+                       ts->read_cnt = 0;
+                       return ADS7846_FILTER_IGNORE;
+               }
+       } else {
+               if (++ts->read_rep > ts->debounce_rep) {
+                       /* Got a good reading for this coordinate,
+                        * go for the next one. */
+                       ts->read_cnt = 0;
+                       ts->read_rep = 0;
+                       return ADS7846_FILTER_OK;
+               } else {
+                       /* Read more values that are consistent. */
+                       ts->read_cnt++;
+                       return ADS7846_FILTER_REPEAT;
+               }
+       }
+}
 
-       ts->pendown = (Rt != 0);
-       ts->pending = 0;
+static int ads7846_no_filter(void *ads, int data_idx, int *val)
+{
+       return ADS7846_FILTER_OK;
+}
+
+static void ads7846_rx_val(void *ads)
+{
+       struct ads7846 *ts = ads;
+       struct spi_message *m;
+       struct spi_transfer *t;
+       u16 *rx_val;
+       int val;
+       int action;
+       int status;
+
+       m = &ts->msg[ts->msg_idx];
+       t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
+       rx_val = t->rx_buf;
+
+       /* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
+        * built from two 8 bit values written msb-first.
+        */
+       val = be16_to_cpu(*rx_val) >> 3;
+
+       action = ts->filter(ts->filter_data, ts->msg_idx, &val);
+       switch (action) {
+       case ADS7846_FILTER_REPEAT:
+               break;
+       case ADS7846_FILTER_IGNORE:
+               ts->tc.ignore = 1;
+               /* Last message will contain ads7846_rx() as the
+                * completion function.
+                */
+               m = ts->last_msg;
+               break;
+       case ADS7846_FILTER_OK:
+               *rx_val = val;
+               ts->tc.ignore = 0;
+               m = &ts->msg[++ts->msg_idx];
+               break;
+       default:
+               BUG();
+       }
+       status = spi_async(ts->spi, m);
+       if (status)
+               dev_err(&ts->spi->dev, "spi_async --> %d\n",
+                               status);
+}
 
-       if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
-               if (ts->pendown)
-                       mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
-               else if (ts->irq_disabled) {
+static enum hrtimer_restart ads7846_timer(struct hrtimer *handle)
+{
+       struct ads7846  *ts = container_of(handle, struct ads7846, timer);
+       int             status = 0;
+
+       spin_lock_irq(&ts->lock);
+
+       if (unlikely(!ts->get_pendown_state() ||
+                    device_suspended(&ts->spi->dev))) {
+               if (ts->pendown) {
+                       struct input_dev *input = ts->input;
+
+                       input_report_key(input, BTN_TOUCH, 0);
+                       input_report_abs(input, ABS_PRESSURE, 0);
+                       input_sync(input);
+
+                       ts->pendown = 0;
+#ifdef VERBOSE
+                       dev_dbg(&ts->spi->dev, "UP\n");
+#endif
+               }
+
+               /* measurement cycle ended */
+               if (!device_suspended(&ts->spi->dev)) {
                        ts->irq_disabled = 0;
                        enable_irq(ts->spi->irq);
                }
+               ts->pending = 0;
+       } else {
+               /* pen is still down, continue with the measurement */
+               ts->msg_idx = 0;
+               status = spi_async(ts->spi, &ts->msg[0]);
+               if (status)
+                       dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
        }
 
-       spin_unlock_irqrestore(&ts->lock, flags);
+       spin_unlock_irq(&ts->lock);
+       return HRTIMER_NORESTART;
 }
 
-static void ads7846_timer(unsigned long handle)
+static irqreturn_t ads7846_irq(int irq, void *handle)
 {
-       struct ads7846  *ts = (void *)handle;
-       int             status = 0;
-       unsigned long   flags;
+       struct ads7846 *ts = handle;
+       unsigned long flags;
 
        spin_lock_irqsave(&ts->lock, flags);
-       if (!ts->pending) {
-               ts->pending = 1;
+       if (likely(ts->get_pendown_state())) {
                if (!ts->irq_disabled) {
+                       /* The ARM do_simple_IRQ() dispatcher doesn't act
+                        * like the other dispatchers:  it will report IRQs
+                        * even after they've been disabled.  We work around
+                        * that here.  (The "generic irq" framework may help...)
+                        */
                        ts->irq_disabled = 1;
                        disable_irq(ts->spi->irq);
+                       ts->pending = 1;
+                       hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_DELAY),
+                                       HRTIMER_MODE_REL);
                }
-               status = spi_async(ts->spi, &ts->msg);
-               if (status)
-                       dev_err(&ts->spi->dev, "spi_async --> %d\n",
-                                       status);
        }
        spin_unlock_irqrestore(&ts->lock, flags);
-}
 
-static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
-{
-       ads7846_timer((unsigned long) handle);
        return IRQ_HANDLED;
 }
 
 /*--------------------------------------------------------------------------*/
 
-static int
-ads7846_suspend(struct spi_device *spi, pm_message_t message)
+/* Must be called with ts->lock held */
+static void ads7846_disable(struct ads7846 *ts)
 {
-       struct ads7846 *ts = dev_get_drvdata(&spi->dev);
-       unsigned long   flags;
-
-       spin_lock_irqsave(&ts->lock, flags);
+       if (ts->disabled)
+               return;
 
-       spi->dev.power.power_state = message;
+       ts->disabled = 1;
 
        /* are we waiting for IRQ, or polling? */
-       if (!ts->pendown) {
-               if (!ts->irq_disabled) {
-                       ts->irq_disabled = 1;
-                       disable_irq(ts->spi->irq);
-               }
+       if (!ts->pending) {
+               ts->irq_disabled = 1;
+               disable_irq(ts->spi->irq);
        } else {
-               /* polling; force a final SPI completion;
-                * that will clean things up neatly
+               /* the timer will run at least once more, and
+                * leave everything in a clean state, IRQ disabled
                 */
-               if (!ts->pending)
-                       mod_timer(&ts->timer, jiffies);
-
-               while (ts->pendown || ts->pending) {
-                       spin_unlock_irqrestore(&ts->lock, flags);
-                       udelay(10);
-                       spin_lock_irqsave(&ts->lock, flags);
+               while (ts->pending) {
+                       spin_unlock_irq(&ts->lock);
+                       msleep(1);
+                       spin_lock_irq(&ts->lock);
                }
        }
 
@@ -389,17 +776,45 @@ ads7846_suspend(struct spi_device *spi, pm_message_t message)
         * leave it that way after every request
         */
 
-       spin_unlock_irqrestore(&ts->lock, flags);
+}
+
+/* Must be called with ts->lock held */
+static void ads7846_enable(struct ads7846 *ts)
+{
+       if (!ts->disabled)
+               return;
+
+       ts->disabled = 0;
+       ts->irq_disabled = 0;
+       enable_irq(ts->spi->irq);
+}
+
+static int ads7846_suspend(struct spi_device *spi, pm_message_t message)
+{
+       struct ads7846 *ts = dev_get_drvdata(&spi->dev);
+
+       spin_lock_irq(&ts->lock);
+
+       ts->is_suspended = 1;
+       ads7846_disable(ts);
+
+       spin_unlock_irq(&ts->lock);
+
        return 0;
+
 }
 
 static int ads7846_resume(struct spi_device *spi)
 {
        struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 
-       ts->irq_disabled = 0;
-       enable_irq(ts->spi->irq);
-       spi->dev.power.power_state = PMSG_ON;
+       spin_lock_irq(&ts->lock);
+
+       ts->is_suspended = 0;
+       ads7846_enable(ts);
+
+       spin_unlock_irq(&ts->lock);
+
        return 0;
 }
 
@@ -408,7 +823,9 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        struct ads7846                  *ts;
        struct input_dev                *input_dev;
        struct ads7846_platform_data    *pdata = spi->dev.platform_data;
+       struct spi_message              *m;
        struct spi_transfer             *x;
+       int                             vref;
        int                             err;
 
        if (!spi->irq) {
@@ -428,11 +845,24 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                return -EINVAL;
        }
 
-       /* We'd set the wordsize to 12 bits ... except that some controllers
-        * will then treat the 8 bit command words as 12 bits (and drop the
-        * four MSBs of the 12 bit result).  Result: inputs must be shifted
-        * to discard the four garbage LSBs.
+       /* REVISIT when the irq can be triggered active-low, or if for some
+        * reason the touchscreen isn't hooked up, we don't need to access
+        * the pendown state.
+        */
+       if (pdata->get_pendown_state == NULL) {
+               dev_dbg(&spi->dev, "no get_pendown_state function?\n");
+               return -EINVAL;
+       }
+
+       /* We'd set TX wordsize 8 bits and RX wordsize to 13 bits ... except
+        * that even if the hardware can do that, the SPI controller driver
+        * may not.  So we stick to very-portable 8 bit words, both RX and TX.
         */
+       spi->bits_per_word = 8;
+       spi->mode = SPI_MODE_0;
+       err = spi_setup(spi);
+       if (err < 0)
+               return err;
 
        ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
        input_dev = input_allocate_device();
@@ -442,27 +872,52 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        }
 
        dev_set_drvdata(&spi->dev, ts);
-       spi->dev.power.power_state = PMSG_ON;
 
        ts->spi = spi;
        ts->input = input_dev;
 
-       init_timer(&ts->timer);
-       ts->timer.data = (unsigned long) ts;
+       hrtimer_init(&ts->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        ts->timer.function = ads7846_timer;
 
+       spin_lock_init(&ts->lock);
+
        ts->model = pdata->model ? : 7846;
        ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
        ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
+       ts->pressure_max = pdata->pressure_max ? : ~0;
+
+       if (pdata->filter != NULL) {
+               if (pdata->filter_init != NULL) {
+                       err = pdata->filter_init(pdata, &ts->filter_data);
+                       if (err < 0)
+                               goto err_free_mem;
+               }
+               ts->filter = pdata->filter;
+               ts->filter_cleanup = pdata->filter_cleanup;
+       } else if (pdata->debounce_max) {
+               ts->debounce_max = pdata->debounce_max;
+               if (ts->debounce_max < 2)
+                       ts->debounce_max = 2;
+               ts->debounce_tol = pdata->debounce_tol;
+               ts->debounce_rep = pdata->debounce_rep;
+               ts->filter = ads7846_debounce;
+               ts->filter_data = ts;
+       } else
+               ts->filter = ads7846_no_filter;
+       ts->get_pendown_state = pdata->get_pendown_state;
+
+       if (pdata->penirq_recheck_delay_usecs)
+               ts->penirq_recheck_delay_usecs =
+                               pdata->penirq_recheck_delay_usecs;
 
        snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
 
        input_dev->name = "ADS784x Touchscreen";
        input_dev->phys = ts->phys;
-       input_dev->cdev.dev = &spi->dev;
+       input_dev->dev.parent = &spi->dev;
 
-       input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
-       input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
+       input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+       input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
        input_set_abs_params(input_dev, ABS_X,
                        pdata->x_min ? : 0,
                        pdata->x_max ? : MAX_12BIT,
@@ -474,99 +929,207 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        input_set_abs_params(input_dev, ABS_PRESSURE,
                        pdata->pressure_min, pdata->pressure_max, 0, 0);
 
+       vref = pdata->keep_vref_on;
+
        /* set up the transfers to read touchscreen state; this assumes we
         * use formula #2 for pressure, not #3.
         */
-       INIT_LIST_HEAD(&ts->msg.transfers);
+       m = &ts->msg[0];
        x = ts->xfer;
 
+       spi_message_init(m);
+
        /* y- still on; turn on only y+ (and ADC) */
-       ts->read_y = READ_Y;
+       ts->read_y = READ_Y(vref);
        x->tx_buf = &ts->read_y;
        x->len = 1;
-       spi_message_add_tail(x, &ts->msg);
+       spi_message_add_tail(x, m);
 
        x++;
        x->rx_buf = &ts->tc.y;
        x->len = 2;
-       spi_message_add_tail(x, &ts->msg);
+       spi_message_add_tail(x, m);
+
+       /* the first sample after switching drivers can be low quality;
+        * optionally discard it, using a second one after the signals
+        * have had enough time to stabilize.
+        */
+       if (pdata->settle_delay_usecs) {
+               x->delay_usecs = pdata->settle_delay_usecs;
+
+               x++;
+               x->tx_buf = &ts->read_y;
+               x->len = 1;
+               spi_message_add_tail(x, m);
+
+               x++;
+               x->rx_buf = &ts->tc.y;
+               x->len = 2;
+               spi_message_add_tail(x, m);
+       }
+
+       m->complete = ads7846_rx_val;
+       m->context = ts;
+
+       m++;
+       spi_message_init(m);
+
+       /* turn y- off, x+ on, then leave in lowpower */
+       x++;
+       ts->read_x = READ_X(vref);
+       x->tx_buf = &ts->read_x;
+       x->len = 1;
+       spi_message_add_tail(x, m);
+
+       x++;
+       x->rx_buf = &ts->tc.x;
+       x->len = 2;
+       spi_message_add_tail(x, m);
+
+       /* ... maybe discard first sample ... */
+       if (pdata->settle_delay_usecs) {
+               x->delay_usecs = pdata->settle_delay_usecs;
+
+               x++;
+               x->tx_buf = &ts->read_x;
+               x->len = 1;
+               spi_message_add_tail(x, m);
+
+               x++;
+               x->rx_buf = &ts->tc.x;
+               x->len = 2;
+               spi_message_add_tail(x, m);
+       }
+
+       m->complete = ads7846_rx_val;
+       m->context = ts;
 
        /* turn y+ off, x- on; we'll use formula #2 */
        if (ts->model == 7846) {
+               m++;
+               spi_message_init(m);
+
                x++;
-               ts->read_z1 = READ_Z1;
+               ts->read_z1 = READ_Z1(vref);
                x->tx_buf = &ts->read_z1;
                x->len = 1;
-               spi_message_add_tail(x, &ts->msg);
+               spi_message_add_tail(x, m);
 
                x++;
                x->rx_buf = &ts->tc.z1;
                x->len = 2;
-               spi_message_add_tail(x, &ts->msg);
+               spi_message_add_tail(x, m);
+
+               /* ... maybe discard first sample ... */
+               if (pdata->settle_delay_usecs) {
+                       x->delay_usecs = pdata->settle_delay_usecs;
+
+                       x++;
+                       x->tx_buf = &ts->read_z1;
+                       x->len = 1;
+                       spi_message_add_tail(x, m);
+
+                       x++;
+                       x->rx_buf = &ts->tc.z1;
+                       x->len = 2;
+                       spi_message_add_tail(x, m);
+               }
+
+               m->complete = ads7846_rx_val;
+               m->context = ts;
+
+               m++;
+               spi_message_init(m);
 
                x++;
-               ts->read_z2 = READ_Z2;
+               ts->read_z2 = READ_Z2(vref);
                x->tx_buf = &ts->read_z2;
                x->len = 1;
-               spi_message_add_tail(x, &ts->msg);
+               spi_message_add_tail(x, m);
 
                x++;
                x->rx_buf = &ts->tc.z2;
                x->len = 2;
-               spi_message_add_tail(x, &ts->msg);
+               spi_message_add_tail(x, m);
+
+               /* ... maybe discard first sample ... */
+               if (pdata->settle_delay_usecs) {
+                       x->delay_usecs = pdata->settle_delay_usecs;
+
+                       x++;
+                       x->tx_buf = &ts->read_z2;
+                       x->len = 1;
+                       spi_message_add_tail(x, m);
+
+                       x++;
+                       x->rx_buf = &ts->tc.z2;
+                       x->len = 2;
+                       spi_message_add_tail(x, m);
+               }
+
+               m->complete = ads7846_rx_val;
+               m->context = ts;
        }
 
-       /* turn y- off, x+ on, then leave in lowpower */
+       /* power down */
+       m++;
+       spi_message_init(m);
+
        x++;
-       ts->read_x = READ_X;
-       x->tx_buf = &ts->read_x;
+       ts->pwrdown = PWRDOWN;
+       x->tx_buf = &ts->pwrdown;
        x->len = 1;
-       spi_message_add_tail(x, &ts->msg);
+       spi_message_add_tail(x, m);
 
        x++;
-       x->rx_buf = &ts->tc.x;
+       x->rx_buf = &ts->dummy;
        x->len = 2;
        CS_CHANGE(*x);
-       spi_message_add_tail(x, &ts->msg);
+       spi_message_add_tail(x, m);
 
-       ts->msg.complete = ads7846_rx;
-       ts->msg.context = ts;
+       m->complete = ads7846_rx;
+       m->context = ts;
 
-       if (request_irq(spi->irq, ads7846_irq,
-                       SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
-                       spi->dev.bus_id, ts)) {
+       ts->last_msg = m;
+
+       if (request_irq(spi->irq, ads7846_irq, IRQF_TRIGGER_FALLING,
+                       spi->dev.driver->name, ts)) {
                dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
                err = -EBUSY;
-               goto err_free_mem;
+               goto err_cleanup_filter;
        }
 
+       err = ads784x_hwmon_register(spi, ts);
+       if (err)
+               goto err_free_irq;
+
        dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
 
-       /* take a first sample, leaving nPENIRQ active; avoid
+       /* take a first sample, leaving nPENIRQ active and vREF off; avoid
         * the touchscreen, in case it's not connected.
         */
        (void) ads7846_read12_ser(&spi->dev,
                          READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
 
-       /* ads7843/7845 don't have temperature sensors, and
-        * use the other sensors a bit differently too
-        */
-       if (ts->model == 7846) {
-               device_create_file(&spi->dev, &dev_attr_temp0);
-               device_create_file(&spi->dev, &dev_attr_temp1);
-       }
-       if (ts->model != 7845)
-               device_create_file(&spi->dev, &dev_attr_vbatt);
-       device_create_file(&spi->dev, &dev_attr_vaux);
+       err = sysfs_create_group(&spi->dev.kobj, &ads784x_attr_group);
+       if (err)
+               goto err_remove_hwmon;
 
        err = input_register_device(input_dev);
        if (err)
-               goto err_free_irq;
+               goto err_remove_attr_group;
 
        return 0;
 
+ err_remove_attr_group:
+       sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);
+ err_remove_hwmon:
+       ads784x_hwmon_unregister(spi, ts);
  err_free_irq:
        free_irq(spi->irq, ts);
+ err_cleanup_filter:
+       if (ts->filter_cleanup)
+               ts->filter_cleanup(ts->filter_data);
  err_free_mem:
        input_free_device(input_dev);
        kfree(ts);
@@ -577,20 +1140,20 @@ static int __devexit ads7846_remove(struct spi_device *spi)
 {
        struct ads7846          *ts = dev_get_drvdata(&spi->dev);
 
+       ads784x_hwmon_unregister(spi, ts);
+       input_unregister_device(ts->input);
+
        ads7846_suspend(spi, PMSG_SUSPEND);
+
+       sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);
+
        free_irq(ts->spi->irq, ts);
-       if (ts->irq_disabled)
-               enable_irq(ts->spi->irq);
+       /* suspend left the IRQ disabled */
+       enable_irq(ts->spi->irq);
 
-       if (ts->model == 7846) {
-               device_remove_file(&spi->dev, &dev_attr_temp0);
-               device_remove_file(&spi->dev, &dev_attr_temp1);
-       }
-       if (ts->model != 7845)
-               device_remove_file(&spi->dev, &dev_attr_vbatt);
-       device_remove_file(&spi->dev, &dev_attr_vaux);
+       if (ts->filter_cleanup)
+               ts->filter_cleanup(ts->filter_data);
 
-       input_unregister_device(ts->input);
        kfree(ts);
 
        dev_dbg(&spi->dev, "unregistered touchscreen\n");