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ads7846.c

/*
 * 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
 *    Copyright (C) 2004-2005 Richard Purdie
 *  - omap_ts.[hc], ads7846.h, ts_osk.c
 *    Copyright (C) 2002 MontaVista Software
 *    Copyright (C) 2004 Texas Instruments
 *    Copyright (C) 2005 Dirk Behme
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 */
#include <linux/hwmon.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
#include <asm/irq.h>

#ifdef      CONFIG_ARM
#include <asm/mach-types.h>
#ifdef      CONFIG_ARCH_OMAP
#include <asm/arch/gpio.h>
#endif
#endif


/*
 * 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.
 *
 * 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_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 */)

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 *** and range adjustment.
       */
      u16   x;
      u16   y;
      u16   z1, z2;
      int   ignore;
};

struct ads7846 {
      struct input_dev  *input;
      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, pwrdown;
      u16               dummy;            /* for the pwrdown read */
      struct ts_event         tc;

      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 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;

      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? */
#if   0
#define     CS_CHANGE(xfer)   ((xfer).cs_change = 1)
#else
#define     CS_CHANGE(xfer)   ((xfer).cs_change = 0)
#endif

/*--------------------------------------------------------------------------*/

/* The ADS7846 has touchscreen and other sensors.
 * Earlier ads784x chips are somewhat compatible.
 */
#define     ADS_START         (1 << 7)
#define     ADS_A2A1A0_d_y          (1 << 4)    /* differential */
#define     ADS_A2A1A0_d_z1         (3 << 4)    /* differential */
#define     ADS_A2A1A0_d_z2         (4 << 4)    /* differential */
#define     ADS_A2A1A0_d_x          (5 << 4)    /* differential */
#define     ADS_A2A1A0_temp0  (0 << 4)    /* non-differential */
#define     ADS_A2A1A0_vbatt  (2 << 4)    /* non-differential */
#define     ADS_A2A1A0_vaux         (6 << 4)    /* non-differential */
#define     ADS_A2A1A0_temp1  (7 << 4)    /* non-differential */
#define     ADS_8_BIT         (1 << 3)
#define     ADS_12_BIT        (0 << 3)
#define     ADS_SER                 (1 << 2)    /* non-differential */
#define     ADS_DFR                 (0 << 2)    /* differential */
#define     ADS_PD10_PDOWN          (0 << 0)    /* lowpower mode + penirq */
#define     ADS_PD10_ADC_ON         (1 << 0)    /* ADC on */
#define     ADS_PD10_REF_ON         (2 << 0)    /* vREF on + penirq */
#define     ADS_PD10_ALL_ON         (3 << 0)    /* ADC + vREF on */

#define     MAX_12BIT   ((1<<12)-1)

/* leave ADC powered up (disables penirq) between differential samples */
#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(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
 */
#define     READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
      | ADS_12_BIT | ADS_SER)

#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;
      u8                command;
      u8                ref_off;
      u16               scratch;
      __be16                  sample;
      struct spi_message      msg;
      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 dev->power.power_state.event != PM_EVENT_ON || 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, GFP_KERNEL);
      int               status;
      int               sample;
      int               use_internal;

      if (!req)
            return -ENOMEM;

      spi_message_init(&req->msg);

      /* FIXME boards with ads7846 might use external vref instead ... */
      use_internal = (ts->model == 7846);

      /* 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 ... */

      /* 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);

      ts->irq_disabled = 1;
      disable_irq(spi->irq);
      status = spi_sync(spi, &req->msg);
      ts->irq_disabled = 0;
      enable_irq(spi->irq);

      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;
}

#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(var) | ADS_PD10_ALL_ON); \
      if (v < 0) \
            return v; \
      return sprintf(buf, "%u\n", adjust(ts, v)); \
} \
static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);


/* 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,
};

/*--------------------------------------------------------------------------*/

/*
 * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 * to retrieve touchscreen status.
 *
 * The SPI transfer completion callback does the real work.  It reports
 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 */

static void ads7846_rx(void *ads)
{
      struct ads7846          *ts = ads;
      unsigned          Rt;
      u16               x, y, z1, z2;

      /* ads7846_rx_val() did in-place conversion (including byteswap) from
       * on-the-wire format as part of debouncing to get stable readings.
       */
      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 (likely(x && z1)) {
            /* compute touch pressure resistance using equation #2 */
            Rt = z2;
            Rt -= z1;
            Rt *= x;
            Rt *= ts->x_plate_ohms;
            Rt /= z1;
            Rt = (Rt + 2047) >> 12;
      } else
            Rt = 0;

      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->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;
      }

      /* 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;
      }

      /* 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);

            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;
            }
      }
}

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);
}

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_irq(&ts->lock);
      return HRTIMER_NORESTART;
}

static irqreturn_t ads7846_irq(int irq, void *handle)
{
      struct ads7846 *ts = handle;
      unsigned long flags;

      spin_lock_irqsave(&ts->lock, flags);
      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);
            }
      }
      spin_unlock_irqrestore(&ts->lock, flags);

      return IRQ_HANDLED;
}

/*--------------------------------------------------------------------------*/

/* Must be called with ts->lock held */
static void ads7846_disable(struct ads7846 *ts)
{
      if (ts->disabled)
            return;

      ts->disabled = 1;

      /* are we waiting for IRQ, or polling? */
      if (!ts->pending) {
            ts->irq_disabled = 1;
            disable_irq(ts->spi->irq);
      } else {
            /* the timer will run at least once more, and
             * leave everything in a clean state, IRQ disabled
             */
            while (ts->pending) {
                  spin_unlock_irq(&ts->lock);
                  msleep(1);
                  spin_lock_irq(&ts->lock);
            }
      }

      /* we know the chip's in lowpower mode since we always
       * leave it that way after every request
       */

}

/* 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);

      spi->dev.power.power_state = message;
      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);

      spin_lock_irq(&ts->lock);

      spi->dev.power.power_state = PMSG_ON;
      ads7846_enable(ts);

      spin_unlock_irq(&ts->lock);

      return 0;
}

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) {
            dev_dbg(&spi->dev, "no IRQ?\n");
            return -ENODEV;
      }

      if (!pdata) {
            dev_dbg(&spi->dev, "no platform data?\n");
            return -ENODEV;
      }

      /* don't exceed max specified sample rate */
      if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
            dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
                        (spi->max_speed_hz/SAMPLE_BITS)/1000);
            return -EINVAL;
      }

      /* 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();
      if (!ts || !input_dev) {
            err = -ENOMEM;
            goto err_free_mem;
      }

      dev_set_drvdata(&spi->dev, ts);
      spi->dev.power.power_state = PMSG_ON;

      ts->spi = spi;
      ts->input = input_dev;

      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->dev.parent = &spi->dev;

      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,
                  0, 0);
      input_set_abs_params(input_dev, ABS_Y,
                  pdata->y_min ? : 0,
                  pdata->y_max ? : MAX_12BIT,
                  0, 0);
      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.
       */
      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(vref);
      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);

      /* 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(vref);
            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);

            /* ... 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(vref);
            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);

            /* ... 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;
      }

      /* power down */
      m++;
      spi_message_init(m);

      x++;
      ts->pwrdown = PWRDOWN;
      x->tx_buf = &ts->pwrdown;
      x->len = 1;
      spi_message_add_tail(x, m);

      x++;
      x->rx_buf = &ts->dummy;
      x->len = 2;
      CS_CHANGE(*x);
      spi_message_add_tail(x, m);

      m->complete = ads7846_rx;
      m->context = 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_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 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);

      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_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);
      return err;
}

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);
      /* suspend left the IRQ disabled */
      enable_irq(ts->spi->irq);

      if (ts->filter_cleanup)
            ts->filter_cleanup(ts->filter_data);

      kfree(ts);

      dev_dbg(&spi->dev, "unregistered touchscreen\n");
      return 0;
}

static struct spi_driver ads7846_driver = {
      .driver = {
            .name = "ads7846",
            .bus  = &spi_bus_type,
            .owner      = THIS_MODULE,
      },
      .probe            = ads7846_probe,
      .remove           = __devexit_p(ads7846_remove),
      .suspend    = ads7846_suspend,
      .resume           = ads7846_resume,
};

static int __init ads7846_init(void)
{
      /* grr, board-specific init should stay out of drivers!! */

#ifdef      CONFIG_ARCH_OMAP
      if (machine_is_omap_osk()) {
            /* GPIO4 = PENIRQ; GPIO6 = BUSY */
            omap_request_gpio(4);
            omap_set_gpio_direction(4, 1);
            omap_request_gpio(6);
            omap_set_gpio_direction(6, 1);
      }
      // also TI 1510 Innovator, bitbanging through FPGA
      // also Nokia 770
      // also Palm Tungsten T2
#endif

      // PXA:
      // also Dell Axim X50
      // also HP iPaq H191x/H192x/H415x/H435x
      // also Intel Lubbock (additional to UCB1400; as temperature sensor)
      // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)

      // Atmel at91sam9261-EK uses ads7843

      // also various AMD Au1x00 devel boards

      return spi_register_driver(&ads7846_driver);
}
module_init(ads7846_init);

static void __exit ads7846_exit(void)
{
      spi_unregister_driver(&ads7846_driver);

#ifdef      CONFIG_ARCH_OMAP
      if (machine_is_omap_osk()) {
            omap_free_gpio(4);
            omap_free_gpio(6);
      }
#endif

}
module_exit(ads7846_exit);

MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
MODULE_LICENSE("GPL");

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