/*
   * 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/gpio.h>

  #include <linux/spi/spi.h>
  #include <linux/spi/ads7846.h>

  #include <asm/irq.h>

  /*

   * This code has been heavily tested on a Nokia 770, and lightly

   * tested on other ads7846 devices (OSK/Mistral, Lubbock, Spitz).

   * 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;

  };

  /*
   * We allocate this separately to avoid cache line sharing issues when
   * driver is used with DMA-based SPI controllers (like atmel_spi) on
   * systems where main memory is not DMA-coherent (most non-x86 boards).
   */
  struct ads7846_packet {
  	u8			read_x, read_y, read_z1, read_z2, pwrdown;
  	u16			dummy;		/* for the pwrdown read */
  	struct ts_event		tc;
  };

  struct ads7846 {

  	struct input_dev	*input;

  	char			phys[32];

  	char			name[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_mv;

  	u16			vref_delay_usecs;
  	u16			x_plate_ohms;

  	u16			pressure_max;

  	bool			swap_xy;

  	struct ads7846_packet	*packet;

  	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;

  	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);

  	int			gpio_pendown;

  
  	void			(*wait_for_sync)(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.

   */
  
  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 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, GFP_KERNEL);

  	int			status;

  	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 */

  		status = be16_to_cpu(req->sample);
  		status = status >> 3;
  		status &= 0x0fff;

  	}

  	kfree(req);

  	return status;

  }

  #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
  ", adjust(ts, v)); \

  } \
  static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);

  /* Sysfs conventions report temperatures in millidegrees Celsius.

   * 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 *= ts->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 (!ts->vref_mv) {

  			dev_dbg(&spi->dev, "assuming 2.5V internal vREF
  ");

  			ts->vref_mv = 2500;

  		}
  		break;
  	case 7845:
  	case 7843:

  		if (!ts->vref_mv) {

  			dev_warn(&spi->dev,
  				"external vREF for ADS%d not specified
  ",
  				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
  ", 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
  ", 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
  ", 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);

  	unsigned long i;

  
  	if (strict_strtoul(buf, 10, &i))
  		return -EINVAL;

  	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,

  };

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

  static int get_pendown_state(struct ads7846 *ts)
  {
  	if (ts->get_pendown_state)
  		return ts->get_pendown_state();
  
  	return !gpio_get_value(ts->gpio_pendown);
  }

  static void null_wait_for_sync(void)
  {
  }

  /*
   * 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;

  	struct ads7846_packet	*packet = ts->packet;

  	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 = packet->tc.x;
  	y = packet->tc.y;
  	z1 = packet->tc.z1;
  	z2 = packet->tc.z2;

  
  	/* range filtering */
  	if (x == MAX_12BIT)
  		x = 0;

  	if (ts->model == 7843) {
  		Rt = ts->pressure_max / 2;
  	} else 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;

  	}

  	/* 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 (packet->tc.ignore || Rt > ts->pressure_max) {

  		dev_vdbg(&ts->spi->dev, "ignored %d pressure %d
  ",
  			 packet->tc.ignore, Rt);

  		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 (!get_pendown_state(ts))

  			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;

  			dev_vdbg(&ts->spi->dev, "DOWN
  ");

  		}

  
  		if (ts->swap_xy)
  			swap(x, y);

  		input_report_abs(input, ABS_X, x);
  		input_report_abs(input, ABS_Y, y);

  		input_report_abs(input, ABS_PRESSURE, ts->pressure_max - Rt);

  		input_sync(input);

  		dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d
  ", x, y, Rt);

  	}

  	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 ads7846_packet *packet = ts->packet;

  	struct spi_message *m;
  	struct spi_transfer *t;

  	int val;
  	int action;
  	int status;
  
  	m = &ts->msg[ts->msg_idx];
  	t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

  
  	/* 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_cpup((__be16 *)t->rx_buf) >> 3;

  
  	action = ts->filter(ts->filter_data, ts->msg_idx, &val);
  	switch (action) {
  	case ADS7846_FILTER_REPEAT:
  		break;
  	case ADS7846_FILTER_IGNORE:

  		packet->tc.ignore = 1;

  		/* Last message will contain ads7846_rx() as the
  		 * completion function.
  		 */
  		m = ts->last_msg;
  		break;
  	case ADS7846_FILTER_OK:

  		*(u16 *)t->rx_buf = val;

  		packet->tc.ignore = 0;

  		m = &ts->msg[++ts->msg_idx];
  		break;
  	default:
  		BUG();

  	}

  	ts->wait_for_sync();

  	status = spi_async(ts->spi, m);
  	if (status)
  		dev_err(&ts->spi->dev, "spi_async --> %d
  ",
  				status);
  }

  static enum hrtimer_restart ads7846_timer(struct hrtimer *handle)

  {

  	struct ads7846	*ts = container_of(handle, struct ads7846, timer);

  	int		status = 0;

  	spin_lock(&ts->lock);

  	if (unlikely(!get_pendown_state(ts) ||

  		     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;

  			dev_vdbg(&ts->spi->dev, "UP
  ");

  		}

  		/* 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;

  		ts->wait_for_sync();

  		status = spi_async(ts->spi, &ts->msg[0]);
  		if (status)
  			dev_err(&ts->spi->dev, "spi_async --> %d
  ", status);
  	}

  	spin_unlock(&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(get_pendown_state(ts))) {

  		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_nosync(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);

  	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);

  	spin_lock_irq(&ts->lock);

  	ts->is_suspended = 0;

  	ads7846_enable(ts);
  
  	spin_unlock_irq(&ts->lock);

  	return 0;
  }

  static int __devinit setup_pendown(struct spi_device *spi, struct ads7846 *ts)
  {
  	struct ads7846_platform_data *pdata = spi->dev.platform_data;
  	int err;
  
  	/* 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 && !gpio_is_valid(pdata->gpio_pendown)) {
  		dev_err(&spi->dev, "no get_pendown_state nor gpio_pendown?
  ");
  		return -EINVAL;
  	}
  
  	if (pdata->get_pendown_state) {
  		ts->get_pendown_state = pdata->get_pendown_state;
  		return 0;
  	}
  
  	err = gpio_request(pdata->gpio_pendown, "ads7846_pendown");
  	if (err) {
  		dev_err(&spi->dev, "failed to request pendown GPIO%d
  ",
  				pdata->gpio_pendown);
  		return err;
  	}
  
  	ts->gpio_pendown = pdata->gpio_pendown;
  	return 0;
  }

  static int __devinit ads7846_probe(struct spi_device *spi)

  {

  	struct ads7846			*ts;

  	struct ads7846_packet		*packet;

  	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?
  ");

  		return -ENODEV;
  	}
  
  	if (!pdata) {

  		dev_dbg(&spi->dev, "no platform data?
  ");

  		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?
  ",

  				(spi->max_speed_hz/SAMPLE_BITS)/1000);

  		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);

  	packet = kzalloc(sizeof(struct ads7846_packet), GFP_KERNEL);

  	input_dev = input_allocate_device();

  	if (!ts || !packet || !input_dev) {

  		err = -ENOMEM;
  		goto err_free_mem;
  	}

  	dev_set_drvdata(&spi->dev, ts);

  	ts->packet = packet;

  	ts->spi = spi;

  	ts->input = input_dev;

  	ts->vref_mv = pdata->vref_mv;

  	ts->swap_xy = pdata->swap_xy;

  	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;

  
  	err = setup_pendown(spi, ts);
  	if (err)
  		goto err_cleanup_filter;

  	if (pdata->penirq_recheck_delay_usecs)
  		ts->penirq_recheck_delay_usecs =
  				pdata->penirq_recheck_delay_usecs;

  	ts->wait_for_sync = pdata->wait_for_sync ? : null_wait_for_sync;

  	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&spi->dev));

  	snprintf(ts->name, sizeof(ts->name), "ADS%d Touchscreen", ts->model);

  	input_dev->name = ts->name;

  	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) */

  	packet->read_y = READ_Y(vref);
  	x->tx_buf = &packet->read_y;

  	x->len = 1;

  	spi_message_add_tail(x, m);

  	x++;

  	x->rx_buf = &packet->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 = &packet->read_y;

  		x->len = 1;
  		spi_message_add_tail(x, m);
  
  		x++;

  		x->rx_buf = &packet->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++;

  	packet->read_x = READ_X(vref);
  	x->tx_buf = &packet->read_x;

  	x->len = 1;
  	spi_message_add_tail(x, m);
  
  	x++;

  	x->rx_buf = &packet->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 = &packet->read_x;

  		x->len = 1;
  		spi_message_add_tail(x, m);
  
  		x++;

  		x->rx_buf = &packet->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++;

  		packet->read_z1 = READ_Z1(vref);
  		x->tx_buf = &packet->read_z1;

  		x->len = 1;

  		spi_message_add_tail(x, m);

  		x++;

  		x->rx_buf = &packet->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 = &packet->read_z1;

  			x->len = 1;
  			spi_message_add_tail(x, m);
  
  			x++;

  			x->rx_buf = &packet->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++;

  		packet->read_z2 = READ_Z2(vref);
  		x->tx_buf = &packet->read_z2;

  		x->len = 1;

  		spi_message_add_tail(x, m);

  		x++;

  		x->rx_buf = &packet->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 = &packet->read_z2;

  			x->len = 1;
  			spi_message_add_tail(x, m);
  
  			x++;

  			x->rx_buf = &packet->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++;

  	packet->pwrdown = PWRDOWN;
  	x->tx_buf = &packet->pwrdown;

  	x->len = 1;

  	spi_message_add_tail(x, m);

  
  	x++;

  	x->rx_buf = &packet->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_info(&spi->dev,
  			"trying pin change workaround on irq %d
  ", spi->irq);
  		err = request_irq(spi->irq, ads7846_irq,
  				  IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
  				  spi->dev.driver->name, ts);
  		if (err) {
  			dev_dbg(&spi->dev, "irq %d busy?
  ", spi->irq);
  			goto err_free_gpio;
  		}

  	}

  	err = ads784x_hwmon_register(spi, ts);
  	if (err)
  		goto err_free_irq;

  	dev_info(&spi->dev, "touchscreen, irq %d
  ", 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_free_gpio:
  	if (ts->gpio_pendown != -1)
  		gpio_free(ts->gpio_pendown);

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

   err_free_mem:
  	input_free_device(input_dev);

  	kfree(packet);

  	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->gpio_pendown != -1)
  		gpio_free(ts->gpio_pendown);

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

  	kfree(ts->packet);

  	kfree(ts);

  	dev_dbg(&spi->dev, "unregistered touchscreen
  ");

  	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)
  {

  	return spi_register_driver(&ads7846_driver);

  }
  module_init(ads7846_init);
  
  static void __exit ads7846_exit(void)
  {

  	spi_unregister_driver(&ads7846_driver);

  }
  module_exit(ads7846_exit);
  
  MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("spi:ads7846");