Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1435 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
new file mode 100644
index 000000000..bed68a68f
--- /dev/null
+++ b/drivers/input/touchscreen/ads7846.c
@@ -0,0 +1,1435 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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
+ */
+#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/input/touchscreen.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/unaligned.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 ads7846_buf {
+	u8 cmd;
+	__be16 data;
+} __packed;
+
+struct ads7846_buf_layout {
+	unsigned int offset;
+	unsigned int count;
+	unsigned int skip;
+};
+
+/*
+ * 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 {
+	unsigned int count;
+	unsigned int count_skip;
+	unsigned int cmds;
+	unsigned int last_cmd_idx;
+	struct ads7846_buf_layout l[5];
+	struct ads7846_buf *rx;
+	struct ads7846_buf *tx;
+
+	struct ads7846_buf pwrdown_cmd;
+
+	bool ignore;
+	u16 x, y, z1, z2;
+};
+
+struct ads7846 {
+	struct input_dev	*input;
+	char			phys[32];
+	char			name[32];
+
+	struct spi_device	*spi;
+	struct regulator	*reg;
+
+	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 touchscreen_properties core_prop;
+
+	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;
+	int			(*get_pendown_state)(void);
+	int			gpio_pendown;
+
+	void			(*wait_for_sync)(void);
+};
+
+enum ads7846_filter {
+	ADS7846_FILTER_OK,
+	ADS7846_FILTER_REPEAT,
+	ADS7846_FILTER_IGNORE,
+};
+
+/* 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))
+
+/* Order commands in the most optimal way to reduce Vref switching and
+ * settling time:
+ * Measure:  X; Vref: X+, X-; IN: Y+
+ * Measure:  Y; Vref: Y+, Y-; IN: X+
+ * Measure: Z1; Vref: Y+, X-; IN: X+
+ * Measure: Z2; Vref: Y+, X-; IN: Y-
+ */
+enum ads7846_cmds {
+	ADS7846_X,
+	ADS7846_Y,
+	ADS7846_Z1,
+	ADS7846_Z2,
+	ADS7846_PWDOWN,
+};
+
+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 ads7846_report_pen_up(struct ads7846 *ts)
+{
+	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 = false;
+	dev_vdbg(&ts->spi->dev, "UP\n");
+}
+
+/* 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);
+	}
+}
+
+/* Must be called with ts->lock held */
+static void ads7846_restart(struct ads7846 *ts)
+{
+	if (!ts->disabled && !ts->suspended) {
+		/* Check if pen was released since last stop */
+		if (ts->pendown && !get_pendown_state(ts))
+			ads7846_report_pen_up(ts);
+
+		/* Tell IRQ thread that it may poll the device. */
+		ts->stopped = false;
+		mb();
+		enable_irq(ts->spi->irq);
+	}
+}
+
+/* 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
+	 */
+}
+
+/* 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);
+}
+
+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);
+}
+
+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);
+}
+
+/*--------------------------------------------------------------------------*/
+
+/*
+ * 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.value = ts->vref_delay_usecs;
+		req->xfer[1].delay.unit = SPI_DELAY_UNIT_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;
+}
+
+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 = get_unaligned_be16(&req->sample[1]);
+		status = status >> 3;
+		status &= 0x0fff;
+	}
+
+	kfree(req);
+	return status;
+}
+
+#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;
+}
+
+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 umode_t ads7846_is_visible(struct kobject *kobj, struct attribute *attr,
+				  int index)
+{
+	struct device *dev = kobj_to_dev(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;
+}
+
+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 const 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)
+{
+	struct device *hwmon;
+
+	/* 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;
+	}
+
+	hwmon = devm_hwmon_device_register_with_groups(&spi->dev,
+						       spi->modalias, ts,
+						       ads7846_attr_groups);
+
+	return PTR_ERR_OR_ZERO(hwmon);
+}
+
+#else
+static inline int ads784x_hwmon_register(struct spi_device *spi,
+					 struct ads7846 *ts)
+{
+	return 0;
+}
+#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);
+}
+
+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);
+	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;
+}
+
+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 const struct attribute_group ads784x_attr_group = {
+	.attrs = ads784x_attributes,
+};
+
+/*--------------------------------------------------------------------------*/
+
+static void null_wait_for_sync(void)
+{
+}
+
+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;
+		}
+	}
+}
+
+static int ads7846_no_filter(void *ads, int data_idx, int *val)
+{
+	return ADS7846_FILTER_OK;
+}
+
+static int ads7846_get_value(struct ads7846_buf *buf)
+{
+	int value;
+
+	value = be16_to_cpup(&buf->data);
+
+	/* enforce ADC output is 12 bits width */
+	return (value >> 3) & 0xfff;
+}
+
+static void ads7846_set_cmd_val(struct ads7846 *ts, enum ads7846_cmds cmd_idx,
+				u16 val)
+{
+	struct ads7846_packet *packet = ts->packet;
+
+	switch (cmd_idx) {
+	case ADS7846_Y:
+		packet->y = val;
+		break;
+	case ADS7846_X:
+		packet->x = val;
+		break;
+	case ADS7846_Z1:
+		packet->z1 = val;
+		break;
+	case ADS7846_Z2:
+		packet->z2 = val;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+	}
+}
+
+static u8 ads7846_get_cmd(enum ads7846_cmds cmd_idx, int vref)
+{
+	switch (cmd_idx) {
+	case ADS7846_Y:
+		return READ_Y(vref);
+	case ADS7846_X:
+		return READ_X(vref);
+
+	/* 7846 specific commands  */
+	case ADS7846_Z1:
+		return READ_Z1(vref);
+	case ADS7846_Z2:
+		return READ_Z2(vref);
+	case ADS7846_PWDOWN:
+		return PWRDOWN;
+	default:
+		WARN_ON_ONCE(1);
+	}
+
+	return 0;
+}
+
+static bool ads7846_cmd_need_settle(enum ads7846_cmds cmd_idx)
+{
+	switch (cmd_idx) {
+	case ADS7846_X:
+	case ADS7846_Y:
+	case ADS7846_Z1:
+	case ADS7846_Z2:
+		return true;
+	case ADS7846_PWDOWN:
+		return false;
+	default:
+		WARN_ON_ONCE(1);
+	}
+
+	return false;
+}
+
+static int ads7846_filter(struct ads7846 *ts)
+{
+	struct ads7846_packet *packet = ts->packet;
+	int action;
+	int val;
+	unsigned int cmd_idx, b;
+
+	packet->ignore = false;
+	for (cmd_idx = packet->last_cmd_idx; cmd_idx < packet->cmds - 1; cmd_idx++) {
+		struct ads7846_buf_layout *l = &packet->l[cmd_idx];
+
+		packet->last_cmd_idx = cmd_idx;
+
+		for (b = l->skip; b < l->count; b++) {
+			val = ads7846_get_value(&packet->rx[l->offset + b]);
+
+			action = ts->filter(ts->filter_data, cmd_idx, &val);
+			if (action == ADS7846_FILTER_REPEAT) {
+				if (b == l->count - 1)
+					return -EAGAIN;
+			} else if (action == ADS7846_FILTER_OK) {
+				ads7846_set_cmd_val(ts, cmd_idx, val);
+				break;
+			} else {
+				packet->ignore = true;
+				return 0;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static void ads7846_read_state(struct ads7846 *ts)
+{
+	struct ads7846_packet *packet = ts->packet;
+	struct spi_message *m;
+	int msg_idx = 0;
+	int error;
+
+	packet->last_cmd_idx = 0;
+
+	while (true) {
+		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->ignore = true;
+			return;
+		}
+
+		error = ads7846_filter(ts);
+		if (error)
+			continue;
+
+		return;
+	}
+}
+
+static void ads7846_report_state(struct ads7846 *ts)
+{
+	struct ads7846_packet *packet = ts->packet;
+	unsigned int Rt;
+	u16 x, y, z1, z2;
+
+	x = packet->x;
+	y = packet->y;
+	if (ts->model == 7845) {
+		z1 = 0;
+		z2 = 0;
+	} else {
+		z1 = packet->z1;
+		z2 = packet->z2;
+	}
+
+	/* range filtering */
+	if (x == MAX_12BIT)
+		x = 0;
+
+	if (ts->model == 7843) {
+		Rt = ts->pressure_max / 2;
+	} else if (ts->model == 7845) {
+		if (get_pendown_state(ts))
+			Rt = ts->pressure_max / 2;
+		else
+			Rt = 0;
+		dev_vdbg(&ts->spi->dev, "x/y: %d/%d, PD %d\n", x, y, Rt);
+	} else if (likely(x && z1)) {
+		/* compute touch pressure resistance using equation #2 */
+		Rt = z2;
+		Rt -= z1;
+		Rt *= ts->x_plate_ohms;
+		Rt = DIV_ROUND_CLOSEST(Rt, 16);
+		Rt *= x;
+		Rt /= z1;
+		Rt = DIV_ROUND_CLOSEST(Rt, 256);
+	} 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->ignore || Rt > ts->pressure_max) {
+		dev_vdbg(&ts->spi->dev, "ignored %d pressure %d\n",
+			 packet->ignore, Rt);
+		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 = true;
+			dev_vdbg(&ts->spi->dev, "DOWN\n");
+		}
+
+		touchscreen_report_pos(input, &ts->core_prop, x, y, false);
+		input_report_abs(input, ABS_PRESSURE, ts->pressure_max - Rt);
+
+		input_sync(input);
+		dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
+	}
+}
+
+static irqreturn_t ads7846_hard_irq(int irq, void *handle)
+{
+	struct ads7846 *ts = handle;
+
+	return get_pendown_state(ts) ? IRQ_WAKE_THREAD : IRQ_HANDLED;
+}
+
+
+static irqreturn_t ads7846_irq(int irq, void *handle)
+{
+	struct ads7846 *ts = handle;
+
+	/* Start with a small delay before checking pendown state */
+	msleep(TS_POLL_DELAY);
+
+	while (!ts->stopped && get_pendown_state(ts)) {
+
+		/* pen is down, continue with the measurement */
+		ads7846_read_state(ts);
+
+		if (!ts->stopped)
+			ads7846_report_state(ts);
+
+		wait_event_timeout(ts->wait, ts->stopped,
+				   msecs_to_jiffies(TS_POLL_PERIOD));
+	}
+
+	if (ts->pendown && !ts->stopped)
+		ads7846_report_pen_up(ts);
+
+	return IRQ_HANDLED;
+}
+
+static int __maybe_unused ads7846_suspend(struct device *dev)
+{
+	struct ads7846 *ts = dev_get_drvdata(dev);
+
+	mutex_lock(&ts->lock);
+
+	if (!ts->suspended) {
+
+		if (!ts->disabled)
+			__ads7846_disable(ts);
+
+		if (device_may_wakeup(&ts->spi->dev))
+			enable_irq_wake(ts->spi->irq);
+
+		ts->suspended = true;
+	}
+
+	mutex_unlock(&ts->lock);
+
+	return 0;
+}
+
+static int __maybe_unused ads7846_resume(struct device *dev)
+{
+	struct ads7846 *ts = dev_get_drvdata(dev);
+
+	mutex_lock(&ts->lock);
+
+	if (ts->suspended) {
+
+		ts->suspended = false;
+
+		if (device_may_wakeup(&ts->spi->dev))
+			disable_irq_wake(ts->spi->irq);
+
+		if (!ts->disabled)
+			__ads7846_enable(ts);
+	}
+
+	mutex_unlock(&ts->lock);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(ads7846_pm, ads7846_suspend, ads7846_resume);
+
+static int ads7846_setup_pendown(struct spi_device *spi,
+				 struct ads7846 *ts,
+				 const struct ads7846_platform_data *pdata)
+{
+	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) {
+		ts->get_pendown_state = pdata->get_pendown_state;
+	} else if (gpio_is_valid(pdata->gpio_pendown)) {
+
+		err = devm_gpio_request_one(&spi->dev, pdata->gpio_pendown,
+					    GPIOF_IN, "ads7846_pendown");
+		if (err) {
+			dev_err(&spi->dev,
+				"failed to request/setup pendown GPIO%d: %d\n",
+				pdata->gpio_pendown, err);
+			return err;
+		}
+
+		ts->gpio_pendown = pdata->gpio_pendown;
+
+		if (pdata->gpio_pendown_debounce)
+			gpio_set_debounce(pdata->gpio_pendown,
+					  pdata->gpio_pendown_debounce);
+	} else {
+		dev_err(&spi->dev, "no get_pendown_state nor gpio_pendown?\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * Set up the transfers to read touchscreen state; this assumes we
+ * use formula #2 for pressure, not #3.
+ */
+static int ads7846_setup_spi_msg(struct ads7846 *ts,
+				  const struct ads7846_platform_data *pdata)
+{
+	struct spi_message *m = &ts->msg[0];
+	struct spi_transfer *x = ts->xfer;
+	struct ads7846_packet *packet = ts->packet;
+	int vref = pdata->keep_vref_on;
+	unsigned int count, offset = 0;
+	unsigned int cmd_idx, b;
+	unsigned long time;
+	size_t size = 0;
+
+	/* time per bit */
+	time = NSEC_PER_SEC / ts->spi->max_speed_hz;
+
+	count = pdata->settle_delay_usecs * NSEC_PER_USEC / time;
+	packet->count_skip = DIV_ROUND_UP(count, 24);
+
+	if (ts->debounce_max && ts->debounce_rep)
+		/* ads7846_debounce_filter() is making ts->debounce_rep + 2
+		 * reads. So we need to get all samples for normal case. */
+		packet->count = ts->debounce_rep + 2;
+	else
+		packet->count = 1;
+
+	if (ts->model == 7846)
+		packet->cmds = 5; /* x, y, z1, z2, pwdown */
+	else
+		packet->cmds = 3; /* x, y, pwdown */
+
+	for (cmd_idx = 0; cmd_idx < packet->cmds; cmd_idx++) {
+		struct ads7846_buf_layout *l = &packet->l[cmd_idx];
+		unsigned int max_count;
+
+		if (ads7846_cmd_need_settle(cmd_idx))
+			max_count = packet->count + packet->count_skip;
+		else
+			max_count = packet->count;
+
+		l->offset = offset;
+		offset += max_count;
+		l->count = max_count;
+		l->skip = packet->count_skip;
+		size += sizeof(*packet->tx) * max_count;
+	}
+
+	packet->tx = devm_kzalloc(&ts->spi->dev, size, GFP_KERNEL);
+	if (!packet->tx)
+		return -ENOMEM;
+
+	packet->rx = devm_kzalloc(&ts->spi->dev, size, GFP_KERNEL);
+	if (!packet->rx)
+		return -ENOMEM;
+
+	if (ts->model == 7873) {
+		/*
+		 * The AD7873 is almost identical to the ADS7846
+		 * keep VREF off during differential/ratiometric
+		 * conversion modes.
+		 */
+		ts->model = 7846;
+		vref = 0;
+	}
+
+	ts->msg_count = 1;
+	spi_message_init(m);
+	m->context = ts;
+
+	for (cmd_idx = 0; cmd_idx < packet->cmds; cmd_idx++) {
+		struct ads7846_buf_layout *l = &packet->l[cmd_idx];
+		u8 cmd = ads7846_get_cmd(cmd_idx, vref);
+
+		for (b = 0; b < l->count; b++)
+			packet->tx[l->offset + b].cmd = cmd;
+	}
+
+	x->tx_buf = packet->tx;
+	x->rx_buf = packet->rx;
+	x->len = size;
+	spi_message_add_tail(x, m);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ads7846_dt_ids[] = {
+	{ .compatible = "ti,tsc2046",	.data = (void *) 7846 },
+	{ .compatible = "ti,ads7843",	.data = (void *) 7843 },
+	{ .compatible = "ti,ads7845",	.data = (void *) 7845 },
+	{ .compatible = "ti,ads7846",	.data = (void *) 7846 },
+	{ .compatible = "ti,ads7873",	.data = (void *) 7873 },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ads7846_dt_ids);
+
+static const struct ads7846_platform_data *ads7846_probe_dt(struct device *dev)
+{
+	struct ads7846_platform_data *pdata;
+	struct device_node *node = dev->of_node;
+	const struct of_device_id *match;
+	u32 value;
+
+	if (!node) {
+		dev_err(dev, "Device does not have associated DT data\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	match = of_match_device(ads7846_dt_ids, dev);
+	if (!match) {
+		dev_err(dev, "Unknown device model\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return ERR_PTR(-ENOMEM);
+
+	pdata->model = (unsigned long)match->data;
+
+	of_property_read_u16(node, "ti,vref-delay-usecs",
+			     &pdata->vref_delay_usecs);
+	of_property_read_u16(node, "ti,vref-mv", &pdata->vref_mv);
+	pdata->keep_vref_on = of_property_read_bool(node, "ti,keep-vref-on");
+
+	pdata->swap_xy = of_property_read_bool(node, "ti,swap-xy");
+
+	of_property_read_u16(node, "ti,settle-delay-usec",
+			     &pdata->settle_delay_usecs);
+	of_property_read_u16(node, "ti,penirq-recheck-delay-usecs",
+			     &pdata->penirq_recheck_delay_usecs);
+
+	of_property_read_u16(node, "ti,x-plate-ohms", &pdata->x_plate_ohms);
+	of_property_read_u16(node, "ti,y-plate-ohms", &pdata->y_plate_ohms);
+
+	of_property_read_u16(node, "ti,x-min", &pdata->x_min);
+	of_property_read_u16(node, "ti,y-min", &pdata->y_min);
+	of_property_read_u16(node, "ti,x-max", &pdata->x_max);
+	of_property_read_u16(node, "ti,y-max", &pdata->y_max);
+
+	/*
+	 * touchscreen-max-pressure gets parsed during
+	 * touchscreen_parse_properties()
+	 */
+	of_property_read_u16(node, "ti,pressure-min", &pdata->pressure_min);
+	if (!of_property_read_u32(node, "touchscreen-min-pressure", &value))
+		pdata->pressure_min = (u16) value;
+	of_property_read_u16(node, "ti,pressure-max", &pdata->pressure_max);
+
+	of_property_read_u16(node, "ti,debounce-max", &pdata->debounce_max);
+	if (!of_property_read_u32(node, "touchscreen-average-samples", &value))
+		pdata->debounce_max = (u16) value;
+	of_property_read_u16(node, "ti,debounce-tol", &pdata->debounce_tol);
+	of_property_read_u16(node, "ti,debounce-rep", &pdata->debounce_rep);
+
+	of_property_read_u32(node, "ti,pendown-gpio-debounce",
+			     &pdata->gpio_pendown_debounce);
+
+	pdata->wakeup = of_property_read_bool(node, "wakeup-source") ||
+			of_property_read_bool(node, "linux,wakeup");
+
+	pdata->gpio_pendown = of_get_named_gpio(dev->of_node, "pendown-gpio", 0);
+
+	return pdata;
+}
+#else
+static const struct ads7846_platform_data *ads7846_probe_dt(struct device *dev)
+{
+	dev_err(dev, "no platform data defined\n");
+	return ERR_PTR(-EINVAL);
+}
+#endif
+
+static void ads7846_regulator_disable(void *regulator)
+{
+	regulator_disable(regulator);
+}
+
+static int ads7846_probe(struct spi_device *spi)
+{
+	const struct ads7846_platform_data *pdata;
+	struct ads7846 *ts;
+	struct device *dev = &spi->dev;
+	struct ads7846_packet *packet;
+	struct input_dev *input_dev;
+	unsigned long irq_flags;
+	int err;
+
+	if (!spi->irq) {
+		dev_dbg(dev, "no IRQ?\n");
+		return -EINVAL;
+	}
+
+	/* don't exceed max specified sample rate */
+	if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
+		dev_err(dev, "f(sample) %d KHz?\n",
+			(spi->max_speed_hz/SAMPLE_BITS)/1000);
+		return -EINVAL;
+	}
+
+	/*
+	 * We'd set TX word size 8 bits and RX word size 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_X_MASK;
+	spi->mode |= SPI_MODE_0;
+	err = spi_setup(spi);
+	if (err < 0)
+		return err;
+
+	ts = devm_kzalloc(dev, sizeof(struct ads7846), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	packet = devm_kzalloc(dev, sizeof(struct ads7846_packet), GFP_KERNEL);
+	if (!packet)
+		return -ENOMEM;
+
+	input_dev = devm_input_allocate_device(dev);
+	if (!input_dev)
+		return -ENOMEM;
+
+	spi_set_drvdata(spi, ts);
+
+	ts->packet = packet;
+	ts->spi = spi;
+	ts->input = input_dev;
+
+	mutex_init(&ts->lock);
+	init_waitqueue_head(&ts->wait);
+
+	pdata = dev_get_platdata(dev);
+	if (!pdata) {
+		pdata = ads7846_probe_dt(dev);
+		if (IS_ERR(pdata))
+			return PTR_ERR(pdata);
+	}
+
+	ts->model = pdata->model ? : 7846;
+	ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
+	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
+	ts->vref_mv = pdata->vref_mv;
+
+	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_filter;
+		ts->filter_data = ts;
+	} else {
+		ts->filter = ads7846_no_filter;
+	}
+
+	err = ads7846_setup_pendown(spi, ts, pdata);
+	if (err)
+		return err;
+
+	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(dev));
+	snprintf(ts->name, sizeof(ts->name), "ADS%d Touchscreen", ts->model);
+
+	input_dev->name = ts->name;
+	input_dev->phys = ts->phys;
+
+	input_dev->id.bustype = BUS_SPI;
+	input_dev->id.product = pdata->model;
+
+	input_set_capability(input_dev, EV_KEY, 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);
+
+	/*
+	 * Parse common framework properties. Must be done here to ensure the
+	 * correct behaviour in case of using the legacy vendor bindings. The
+	 * general binding value overrides the vendor specific one.
+	 */
+	touchscreen_parse_properties(ts->input, false, &ts->core_prop);
+	ts->pressure_max = input_abs_get_max(input_dev, ABS_PRESSURE) ? : ~0;
+
+	/*
+	 * Check if legacy ti,swap-xy binding is used instead of
+	 * touchscreen-swapped-x-y
+	 */
+	if (!ts->core_prop.swap_x_y && pdata->swap_xy) {
+		swap(input_dev->absinfo[ABS_X], input_dev->absinfo[ABS_Y]);
+		ts->core_prop.swap_x_y = true;
+	}
+
+	ads7846_setup_spi_msg(ts, pdata);
+
+	ts->reg = devm_regulator_get(dev, "vcc");
+	if (IS_ERR(ts->reg)) {
+		err = PTR_ERR(ts->reg);
+		dev_err(dev, "unable to get regulator: %d\n", err);
+		return err;
+	}
+
+	err = regulator_enable(ts->reg);
+	if (err) {
+		dev_err(dev, "unable to enable regulator: %d\n", err);
+		return err;
+	}
+
+	err = devm_add_action_or_reset(dev, ads7846_regulator_disable, ts->reg);
+	if (err)
+		return err;
+
+	irq_flags = pdata->irq_flags ? : IRQF_TRIGGER_FALLING;
+	irq_flags |= IRQF_ONESHOT;
+
+	err = devm_request_threaded_irq(dev, spi->irq,
+					ads7846_hard_irq, ads7846_irq,
+					irq_flags, dev->driver->name, ts);
+	if (err && err != -EPROBE_DEFER && !pdata->irq_flags) {
+		dev_info(dev,
+			"trying pin change workaround on irq %d\n", spi->irq);
+		irq_flags |= IRQF_TRIGGER_RISING;
+		err = devm_request_threaded_irq(dev, spi->irq,
+						ads7846_hard_irq, ads7846_irq,
+						irq_flags, dev->driver->name,
+						ts);
+	}
+
+	if (err) {
+		dev_dbg(dev, "irq %d busy?\n", spi->irq);
+		return err;
+	}
+
+	err = ads784x_hwmon_register(spi, ts);
+	if (err)
+		return err;
+
+	dev_info(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.
+	 */
+	if (ts->model == 7845)
+		ads7845_read12_ser(dev, PWRDOWN);
+	else
+		(void) ads7846_read12_ser(dev, READ_12BIT_SER(vaux));
+
+	err = devm_device_add_group(dev, &ads784x_attr_group);
+	if (err)
+		return err;
+
+	err = input_register_device(input_dev);
+	if (err)
+		return err;
+
+	device_init_wakeup(dev, pdata->wakeup);
+
+	/*
+	 * If device does not carry platform data we must have allocated it
+	 * when parsing DT data.
+	 */
+	if (!dev_get_platdata(dev))
+		devm_kfree(dev, (void *)pdata);
+
+	return 0;
+}
+
+static void ads7846_remove(struct spi_device *spi)
+{
+	struct ads7846 *ts = spi_get_drvdata(spi);
+
+	ads7846_stop(ts);
+}
+
+static struct spi_driver ads7846_driver = {
+	.driver = {
+		.name	= "ads7846",
+		.pm	= &ads7846_pm,
+		.of_match_table = of_match_ptr(ads7846_dt_ids),
+	},
+	.probe		= ads7846_probe,
+	.remove		= ads7846_remove,
+};
+
+module_spi_driver(ads7846_driver);
+
+MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:ads7846");