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Release 4.11 drivers/input/touchscreen/ads7846.c

Directory: drivers/input/touchscreen
/*
 * 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/types.h>
#include <linux/hwmon.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/of_device.h>
#include <linux/gpio.h>
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
#include <linux/regulator/consumer.h>
#include <linux/module.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.
 * Support for Analog Devices AD7873 and AD7843 tested.
 *
 * 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	
/* ms delay before the first sample */

#define TS_POLL_PERIOD	5	
/* ms 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 byte order 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;
	
bool	ignore;
	
u8	x_buf[3];
	
u8	y_buf[3];
};

/*
 * 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;
	/* for ads7845 with mpc5121 psc spi we use 3-byte buffers */
	


u8			read_x_cmd[3], read_y_cmd[3], pwrdown_cmd[3];
};


struct ads7846 {
	
struct input_dev	*input;
	
char			phys[32];
	
char			name[32];

	
struct spi_device	*spi;
	
struct regulator	*reg;

#if IS_ENABLED(CONFIG_HWMON)
	
struct device		*hwmon;
#endif

	
u16			model;
	
u16			vref_mv;
	
u16			vref_delay_usecs;
	
u16			x_plate_ohms;
	
u16			pressure_max;

	
bool			swap_xy;
	
bool			use_internal;

	
struct ads7846_packet	*packet;

	
struct spi_transfer	xfer[18];
	
struct spi_message	msg[5];
	
int			msg_count;
	
wait_queue_head_t	wait;

	
bool			pendown;

	
int			read_cnt;
	
int			read_rep;
	
int			last_read;

	
u16			debounce_max;
	
u16			debounce_tol;
	
u16			debounce_rep;

	
u16			penirq_recheck_delay_usecs;

	
struct mutex		lock;
	
bool			stopped;	/* P: lock */
	
bool			disabled;	/* P: lock */
	
bool			suspended;	/* P: lock */

	
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)	
/* low power 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))

/* Must be called with ts->lock held */



static void ads7846_stop(struct ads7846 *ts)
{
	if (!ts->disabled && !ts->suspended) {
		/* Signal IRQ thread to stop polling and disable the handler. */
		ts->stopped = true;
		mb();
		wake_up(&ts->wait);
		disable_irq(ts->spi->irq);
	}
}


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/* Must be called with ts->lock held */



static void ads7846_restart(struct ads7846 *ts)
{
	if (!ts->disabled && !ts->suspended) {
		/* Tell IRQ thread that it may poll the device. */
		ts->stopped = false;
		mb();
		enable_irq(ts->spi->irq);
	}
}


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/* Must be called with ts->lock held */



static void __ads7846_disable(struct ads7846 *ts)
{
	ads7846_stop(ts);
	regulator_disable(ts->reg);

	/*
         * We know the chip's in low power mode since we always
         * leave it that way after every request
         */
}


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/* Must be called with ts->lock held */



static void __ads7846_enable(struct ads7846 *ts)
{
	int error;

	error = regulator_enable(ts->reg);
	if (error != 0)
		dev_err(&ts->spi->dev, "Failed to enable supply: %d\n", error);

	ads7846_restart(ts);
}


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static void ads7846_disable(struct ads7846 *ts)
{
	mutex_lock(&ts->lock);

	if (!ts->disabled) {

		if  (!ts->suspended)
			__ads7846_disable(ts);

		ts->disabled = true;
	}

	mutex_unlock(&ts->lock);
}


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static void ads7846_enable(struct ads7846 *ts)
{
	mutex_lock(&ts->lock);

	if (ts->disabled) {

		ts->disabled = false;

		if (!ts->suspended)
			__ads7846_enable(ts);
	}

	mutex_unlock(&ts->lock);
}


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

/*
 * 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;
	
struct spi_message	msg;
	
struct spi_transfer	xfer[6];
	/*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
         */
	
__be16 sample ____cacheline_aligned;
};


struct ads7845_ser_req {
	
u8			command[3];
	
struct spi_message	msg;
	
struct spi_transfer	xfer[2];
	/*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
         */
	
u8 sample[3] ____cacheline_aligned;
};




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;
	int status;

	req = kzalloc(sizeof *req, GFP_KERNEL);
	if (!req)
		return -ENOMEM;

	spi_message_init(&req->msg);

	/* maybe turn on internal vREF, and let it settle */
	if (ts->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);

		/* Enable reference voltage */
		command |= ADS_PD10_REF_ON;
	}

	/* Enable ADC in every case */
	command |= ADS_PD10_ADC_ON;

	/* 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);

	mutex_lock(&ts->lock);
	ads7846_stop(ts);
	status = spi_sync(spi, &req->msg);
	ads7846_restart(ts);
	mutex_unlock(&ts->lock);

	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;
}


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static int ads7845_read12_ser(struct device *dev, unsigned command)
{
	struct spi_device *spi = to_spi_device(dev);
	struct ads7846 *ts = dev_get_drvdata(dev);
	struct ads7845_ser_req *req;
	int status;

	req = kzalloc(sizeof *req, GFP_KERNEL);
	if (!req)
		return -ENOMEM;

	spi_message_init(&req->msg);

	req->command[0] = (u8) command;
	req->xfer[0].tx_buf = req->command;
	req->xfer[0].rx_buf = req->sample;
	req->xfer[0].len = 3;
	spi_message_add_tail(&req->xfer[0], &req->msg);

	mutex_lock(&ts->lock);
	ads7846_stop(ts);
	status = spi_sync(spi, &req->msg);
	ads7846_restart(ts);
	mutex_unlock(&ts->lock);

	if (status == 0) {
		/* BE12 value, then padding */
		status = be16_to_cpu(*((u16 *)&req->sample[1]));
		status = status >> 3;
		status &= 0x0fff;
	}

	kfree(req);
	return status;
}


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#if IS_ENABLED(CONFIG_HWMON)


#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(&ts->spi->dev, \
                        READ_12BIT_SER(var)); \
        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 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;
}


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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;
}


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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;
}


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SHOW(in0_input, vaux, vaux_adjust)
SHOW(in1_input, vbatt, vbatt_adjust)




static umode_t ads7846_is_visible(struct kobject *kobj, struct attribute *attr,
				  int index)
{
	struct device *dev = container_of(kobj, struct device, kobj);
	struct ads7846 *ts = dev_get_drvdata(dev);

	if (ts->model == 7843 && index < 2)	/* in0, in1 */
		return 0;
	if (ts->model == 7845 && index != 2)	/* in0 */
		return 0;

	return attr->mode;
}


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static struct attribute *ads7846_attributes[] = {
	&dev_attr_temp0.attr,		/* 0 */
	&dev_attr_temp1.attr,		/* 1 */
	&dev_attr_in0_input.attr,	/* 2 */
	&dev_attr_in1_input.attr,	/* 3 */
	NULL,
};


static struct attribute_group ads7846_attr_group = {
	.attrs = ads7846_attributes,
	.is_visible = ads7846_is_visible,
};

__ATTRIBUTE_GROUPS(ads7846_attr);




static int ads784x_hwmon_register(struct spi_device *spi, struct ads7846 *ts)
{
	/* hwmon sensors need a reference voltage */
	switch (ts->model) {
	case 7846:
		if (!ts->vref_mv) {
			dev_dbg(&spi->dev, "assuming 2.5V internal vREF\n");
			ts->vref_mv = 2500;
			ts->use_internal = true;
		}
		break;
	case 7845:
	case 7843:
		if (!ts->vref_mv) {
			dev_warn(&spi->dev,
				"external vREF for ADS%d not specified\n",
				ts->model);
			return 0;
		}
		break;
	}

	ts->hwmon = hwmon_device_register_with_groups(&spi->dev, spi->modalias,
						      ts, ads7846_attr_groups);

	return PTR_ERR_OR_ZERO(ts->hwmon);
}


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static void ads784x_hwmon_unregister(struct spi_device *spi,
				     struct ads7846 *ts)
{
	if (ts->hwmon)
		hwmon_device_unregister(ts->hwmon);
}


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#else



static inline int ads784x_hwmon_register(struct spi_device *spi,
					 struct ads7846 *ts)
{
	return 0;
}


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static inline void ads784x_hwmon_unregister(struct spi_device *spi,
					    struct ads7846 *ts)
{
}

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#endif




static ssize_t ads7846_pen_down_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	struct ads7846 *ts = dev_get_drvdata(dev);

	return sprintf(buf, "%u\n", ts->pendown);
}


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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);
}


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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 int i;
	int err;

	err = kstrtouint(buf, 10, &i);
	if (err)
		return err;

	if (i)
		ads7846_disable(ts);
	else
		ads7846_enable(ts);

	return count;
}


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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);
}


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static void null_wait_for_sync(void)
{
}


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static int ads7846_debounce_filter(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;
		}
	}
}


Contributors
PersonTokensPropCommitsCommitProp
Imre Deak5236.88%342.86%


Jason (Hui) Wang4834.04%114.29%


David Brownell2316.31%114.29%


Hans-Christian Noren Egtvedt96.38%114.29%


Anatolij Gustschin96.38%114.29%


Total141100.00%7100.00%






static int ads7846_no_filter(void *ads, int data_idx, int *val)
{
	return ADS7846_FILTER_OK;
}


Contributors
PersonTokensPropCommitsCommitProp
Imre Deak20100.00%1100.00%


Total20100.00%1100.00%






static int ads7846_get_value(struct ads7846 *ts, struct spi_message *m)
{
	int value;
	struct spi_transfer *t =
		list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

	if (ts->model == 7845) {
		value = be16_to_cpup((__be16 *)&(((char *)t->rx_buf)[1]));
	} else {
		/*
                 * adjust:  on-wire is a must-ignore bit, a BE12 value, then
                 * padding; built from two 8 bit values written msb-first.
                 */
		value = be16_to_cpup((__be16 *)t->rx_buf);
	}

	/* enforce ADC output is 12 bits width */
	return (value >> 3) & 0xfff;
}


Contributors
PersonTokensPropCommitsCommitProp
Anatolij Gustschin4545.00%116.67%


Imre Deak2020.00%116.67%


Andrey Gelman1717.00%116.67%


Jason (Hui) Wang1010.00%116.67%


Harvey Harrison77.00%116.67%


Dmitry Torokhov11.00%116.67%


Total100100.00%6100.00%






static void ads7846_update_value(struct spi_message *m, int val)
{
	struct spi_transfer *t =
		list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

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


Contributors
PersonTokensPropCommitsCommitProp
Jason (Hui) Wang4295.45%133.33%


Imre Deak12.27%133.33%


Anatolij Gustschin12.27%133.33%


Total44100.00%3100.00%






static void ads7846_read_state(struct ads7846 *ts)
{
	struct ads7846_packet *packet = ts->packet;
	struct spi_message *m;
	int msg_idx = 0;
	int val;
	int action;
	int error;

	while (msg_idx < ts->msg_count) {

		ts->wait_for_sync();

		m = &ts->msg[msg_idx];
		error = spi_sync(ts->spi, m);
		if (error) {
			dev_err(&ts->spi->dev, "spi_sync --> %d\n", error);
			packet->tc.ignore = true;
			return;
		}

		/*
                 * Last message is power down request, no need to convert
                 * or filter the value.
                 */
		if (msg_idx < ts->msg_count - 1) {

			val = ads7846_get_value(ts, m);

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

			case ADS7846_FILTER_IGNORE:
				packet->tc.ignore = true;
				msg_idx = ts->msg_count - 1;
				continue;

			case ADS7846_FILTER_OK:
				ads7846_update_value(m, val);
				packet->tc.ignore = false;
				msg_idx++;
				break;

			default:
				BUG();
			}
		} else {
			msg_idx++;
		}
	}
}


Contributors
PersonTokensPropCommitsCommitProp
Jason (Hui) Wang14370.10%114.29%


Imre Deak5325.98%342.86%


David Brownell52.45%114.29%


Dmitry Torokhov20.98%114.29%


Mark Brown10.49%114.29%


Total204100.00%7100.00%






static void ads7846_report_state(struct ads7846 *ts)
{
	struct ads7846_packet *packet = ts->packet;
	unsigned int Rt;
	u16 x, y, z1, z2;

	/*
         * ads7846_get_value() does in-place conversion (including byte swap)
         * from on-the-wire format as part of debouncing to get stable
         * readings.
         */
	if (ts->model == 7845) {
		x = *(u16 *)packet->tc.x_buf;
		y = *(u16 *)packet->tc.y_buf;
		z1 = 0;
		z2 = 0;
	} else {
		x = packet->tc.x;
		y = packet->tc.y;
		z1 = packet->tc.z1;
		z2 = packet->tc.z2;
	}

	/* range filtering */