ads7846.c

linux 内核源代码

/*
 * ADS7846 based touchscreen and sensor driver
 *
 * Copyright (c) 2005 David Brownell
 * Copyright (c) 2006 Nokia Corporation
 * Various changes: Imre Deak <[e-mail]>
 *
 * 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 {