Input: tsc2007 - add iio interface to read external ADC input and temperature

The tsc2007 chip not only has a resistive touch screen controller but
also an external AUX adc imput which can be used for an ambient
light sensor, battery voltage monitoring or any general purpose.

Additionally it can measure the chip temperature.

This extension provides an iio interface for these adc channels.

Since it is not wasting much resources and is very straightforward,
we simply provide all other adc channels as optional iio interfaces
as weel. This can be used for debugging or special applications.

This patch also splits the tsc2007 driver in several source files:
tsc2007.h -- constants, structs and stubs
tsc2007_core.c -- functional parts of the original driver
tsc2007_iio.c -- the optional iio stuff

Makefile magic allows to conditionally link the iio stuff
if CONFIG_IIO=y or =m in a way that it works with
CONFIG_TOUCHSCREEN_TSC2007=m.

Signed-off-by: H. Nikolaus Schaller <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/touchscreen/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called tsc2007.
 
+config TOUCHSCREEN_TSC2007_IIO
+	bool "IIO interface for external ADC input and temperature"
+	depends on TOUCHSCREEN_TSC2007
+	depends on IIO=y || IIO=TOUCHSCREEN_TSC2007
+	help
+	  Saying Y here adds an iio interface to the tsc2007 which
+	  provides values for the AUX input (used for e.g. battery
+	  or ambient light monitoring), temperature and raw input
+	  values.
+
 config TOUCHSCREEN_W90X900
 	tristate "W90P910 touchscreen driver"
 	depends on ARCH_W90X900

drivers/input/touchscreen/Makefile

···
 obj-$(CONFIG_TOUCHSCREEN_TSC200X_CORE)	+= tsc200x-core.o
 obj-$(CONFIG_TOUCHSCREEN_TSC2004)	+= tsc2004.o
 obj-$(CONFIG_TOUCHSCREEN_TSC2005)	+= tsc2005.o
+tsc2007-y := tsc2007_core.o
+tsc2007-$(CONFIG_TOUCHSCREEN_TSC2007_IIO)	+= tsc2007_iio.o
 obj-$(CONFIG_TOUCHSCREEN_TSC2007)	+= tsc2007.o
 obj-$(CONFIG_TOUCHSCREEN_UCB1400)	+= ucb1400_ts.o
 obj-$(CONFIG_TOUCHSCREEN_WACOM_W8001)	+= wacom_w8001.o

drivers/input/touchscreen/tsc2007.c drivers/input/touchscreen/tsc2007_core.c

···
 #include <linux/i2c.h>
 #include <linux/i2c/tsc2007.h>
 #include <linux/of_device.h>
-#include <linux/of.h>
 #include <linux/of_gpio.h>
+#include "tsc2007.h"
 
-#define TSC2007_MEASURE_TEMP0		(0x0 << 4)
-#define TSC2007_MEASURE_AUX		(0x2 << 4)
-#define TSC2007_MEASURE_TEMP1		(0x4 << 4)
-#define TSC2007_ACTIVATE_XN		(0x8 << 4)
-#define TSC2007_ACTIVATE_YN		(0x9 << 4)
-#define TSC2007_ACTIVATE_YP_XN		(0xa << 4)
-#define TSC2007_SETUP			(0xb << 4)
-#define TSC2007_MEASURE_X		(0xc << 4)
-#define TSC2007_MEASURE_Y		(0xd << 4)
-#define TSC2007_MEASURE_Z1		(0xe << 4)
-#define TSC2007_MEASURE_Z2		(0xf << 4)
-
-#define TSC2007_POWER_OFF_IRQ_EN	(0x0 << 2)
-#define TSC2007_ADC_ON_IRQ_DIS0		(0x1 << 2)
-#define TSC2007_ADC_OFF_IRQ_EN		(0x2 << 2)
-#define TSC2007_ADC_ON_IRQ_DIS1		(0x3 << 2)
-
-#define TSC2007_12BIT			(0x0 << 1)
-#define TSC2007_8BIT			(0x1 << 1)
-
-#define	MAX_12BIT			((1 << 12) - 1)
-
-#define ADC_ON_12BIT	(TSC2007_12BIT | TSC2007_ADC_ON_IRQ_DIS0)
-
-#define READ_Y		(ADC_ON_12BIT | TSC2007_MEASURE_Y)
-#define READ_Z1		(ADC_ON_12BIT | TSC2007_MEASURE_Z1)
-#define READ_Z2		(ADC_ON_12BIT | TSC2007_MEASURE_Z2)
-#define READ_X		(ADC_ON_12BIT | TSC2007_MEASURE_X)
-#define PWRDOWN		(TSC2007_12BIT | TSC2007_POWER_OFF_IRQ_EN)
-
-struct ts_event {
-	u16	x;
-	u16	y;
-	u16	z1, z2;
-};
-
-struct tsc2007 {
-	struct input_dev	*input;
-	char			phys[32];
-
-	struct i2c_client	*client;
-
-	u16			model;
-	u16			x_plate_ohms;
-	u16			max_rt;
-	unsigned long		poll_period; /* in jiffies */
-	int			fuzzx;
-	int			fuzzy;
-	int			fuzzz;
-
-	unsigned		gpio;
-	int			irq;
-
-	wait_queue_head_t	wait;
-	bool			stopped;
-
-	int			(*get_pendown_state)(struct device *);
-	void			(*clear_penirq)(void);
-};
-
-static inline int tsc2007_xfer(struct tsc2007 *tsc, u8 cmd)
+int tsc2007_xfer(struct tsc2007 *tsc, u8 cmd)
 {
 	s32 data;
 	u16 val;
···
 	tsc2007_xfer(tsc, PWRDOWN);
 }
 
-static u32 tsc2007_calculate_pressure(struct tsc2007 *tsc, struct ts_event *tc)
+u32 tsc2007_calculate_pressure(struct tsc2007 *tsc, struct ts_event *tc)
 {
 	u32 rt = 0;
 
···
 	return rt;
 }
 
-static bool tsc2007_is_pen_down(struct tsc2007 *ts)
+bool tsc2007_is_pen_down(struct tsc2007 *ts)
 {
 	/*
 	 * NOTE: We can't rely on the pressure to determine the pen down
···
 	while (!ts->stopped && tsc2007_is_pen_down(ts)) {
 
 		/* pen is down, continue with the measurement */
+
+		mutex_lock(&ts->mlock);
 		tsc2007_read_values(ts, &tc);
+		mutex_unlock(&ts->mlock);
 
 		rt = tsc2007_calculate_pressure(ts, &tc);
 
···
 static int tsc2007_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
-	const struct tsc2007_platform_data *pdata = dev_get_platdata(&client->dev);
+	const struct tsc2007_platform_data *pdata =
+		dev_get_platdata(&client->dev);
 	struct tsc2007 *ts;
 	struct input_dev *input_dev;
 	int err;
···
 	ts->client = client;
 	ts->irq = client->irq;
 	ts->input = input_dev;
+
 	init_waitqueue_head(&ts->wait);
+	mutex_init(&ts->mlock);
 
 	snprintf(ts->phys, sizeof(ts->phys),
 		 "%s/input0", dev_name(&client->dev));
···
 	if (err < 0) {
 		dev_err(&client->dev,
 			"Failed to setup chip: %d\n", err);
-		return err;	/* usually, chip does not respond */
+		return err;	/* chip does not respond */
 	}
 
 	err = input_register_device(input_dev);
 	if (err) {
 		dev_err(&client->dev,
 			"Failed to register input device: %d\n", err);
+		return err;
+	}
+
+	err =  tsc2007_iio_configure(ts);
+	if (err) {
+		dev_err(&client->dev,
+			"Failed to register with IIO: %d\n", err);
 		return err;
 	}
 

drivers/input/touchscreen/tsc2007.h

···
+
+/*
+ * Copyright (c) 2008 MtekVision Co., Ltd.
+ *	Kwangwoo Lee <[e-mail]>
+ *
+ * Using code from:
+ *  - ads7846.c
+ *	Copyright (c) 2005 David Brownell
+ *	Copyright (c) 2006 Nokia Corporation
+ *  - 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.
+ */
+
+#ifndef _TSC2007_H
+#define _TSC2007_H
+
+#define TSC2007_MEASURE_TEMP0		(0x0 << 4)
+#define TSC2007_MEASURE_AUX		(0x2 << 4)
+#define TSC2007_MEASURE_TEMP1		(0x4 << 4)
+#define TSC2007_ACTIVATE_XN		(0x8 << 4)
+#define TSC2007_ACTIVATE_YN		(0x9 << 4)
+#define TSC2007_ACTIVATE_YP_XN		(0xa << 4)
+#define TSC2007_SETUP			(0xb << 4)
+#define TSC2007_MEASURE_X		(0xc << 4)
+#define TSC2007_MEASURE_Y		(0xd << 4)
+#define TSC2007_MEASURE_Z1		(0xe << 4)
+#define TSC2007_MEASURE_Z2		(0xf << 4)
+
+#define TSC2007_POWER_OFF_IRQ_EN	(0x0 << 2)
+#define TSC2007_ADC_ON_IRQ_DIS0		(0x1 << 2)
+#define TSC2007_ADC_OFF_IRQ_EN		(0x2 << 2)
+#define TSC2007_ADC_ON_IRQ_DIS1		(0x3 << 2)
+
+#define TSC2007_12BIT			(0x0 << 1)
+#define TSC2007_8BIT			(0x1 << 1)
+
+#define MAX_12BIT			((1 << 12) - 1)
+
+#define ADC_ON_12BIT	(TSC2007_12BIT | TSC2007_ADC_ON_IRQ_DIS0)
+
+#define READ_Y		(ADC_ON_12BIT | TSC2007_MEASURE_Y)
+#define READ_Z1		(ADC_ON_12BIT | TSC2007_MEASURE_Z1)
+#define READ_Z2		(ADC_ON_12BIT | TSC2007_MEASURE_Z2)
+#define READ_X		(ADC_ON_12BIT | TSC2007_MEASURE_X)
+#define PWRDOWN		(TSC2007_12BIT | TSC2007_POWER_OFF_IRQ_EN)
+
+struct ts_event {
+	u16	x;
+	u16	y;
+	u16	z1, z2;
+};
+
+struct tsc2007 {
+	struct input_dev	*input;
+	char			phys[32];
+
+	struct i2c_client	*client;
+
+	u16			model;
+	u16			x_plate_ohms;
+	u16			max_rt;
+	unsigned long		poll_period; /* in jiffies */
+	int			fuzzx;
+	int			fuzzy;
+	int			fuzzz;
+
+	unsigned int		gpio;
+	int			irq;
+
+	wait_queue_head_t	wait;
+	bool			stopped;
+
+	int			(*get_pendown_state)(struct device *);
+	void			(*clear_penirq)(void);
+
+	struct mutex		mlock;
+};
+
+int tsc2007_xfer(struct tsc2007 *tsc, u8 cmd);
+u32 tsc2007_calculate_pressure(struct tsc2007 *tsc,
+					struct ts_event *tc);
+bool tsc2007_is_pen_down(struct tsc2007 *ts);
+
+#if IS_ENABLED(CONFIG_TOUCHSCREEN_TSC2007_IIO)
+/* defined in tsc2007_iio.c */
+int tsc2007_iio_configure(struct tsc2007 *ts);
+#else
+static inline int tsc2007_iio_configure(struct tsc2007 *ts)
+{
+	return 0;
+}
+#endif /* CONFIG_TOUCHSCREEN_TSC2007_IIO */
+
+#endif /* _TSC2007_H */

drivers/input/touchscreen/tsc2007_iio.c

···
+/*
+ * Copyright (c) 2016 Golden Delicious Comp. GmbH&Co. KG
+ *	Nikolaus Schaller <[e-mail]>
+ *
+ *  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/i2c.h>
+#include <linux/iio/iio.h>
+#include "tsc2007.h"
+
+struct tsc2007_iio {
+	struct tsc2007 *ts;
+};
+
+#define TSC2007_CHAN_IIO(_chan, _name, _type, _chan_info) \
+{ \
+	.datasheet_name = _name, \
+	.type = _type, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
+			BIT(_chan_info), \
+	.indexed = 1, \
+	.channel = _chan, \
+}
+
+static const struct iio_chan_spec tsc2007_iio_channel[] = {
+	TSC2007_CHAN_IIO(0, "x", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(1, "y", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(2, "z1", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(3, "z2", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(4, "adc", IIO_VOLTAGE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(5, "rt", IIO_VOLTAGE, IIO_CHAN_INFO_RAW), /* Ohms? */
+	TSC2007_CHAN_IIO(6, "pen", IIO_PRESSURE, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(7, "temp0", IIO_TEMP, IIO_CHAN_INFO_RAW),
+	TSC2007_CHAN_IIO(8, "temp1", IIO_TEMP, IIO_CHAN_INFO_RAW),
+};
+
+static int tsc2007_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct tsc2007_iio *iio = iio_priv(indio_dev);
+	struct tsc2007 *tsc = iio->ts;
+	int adc_chan = chan->channel;
+	int ret = 0;
+
+	if (adc_chan >= ARRAY_SIZE(tsc2007_iio_channel))
+		return -EINVAL;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	mutex_lock(&tsc->mlock);
+
+	switch (chan->channel) {
+	case 0:
+		*val = tsc2007_xfer(tsc, READ_X);
+		break;
+	case 1:
+		*val = tsc2007_xfer(tsc, READ_Y);
+		break;
+	case 2:
+		*val = tsc2007_xfer(tsc, READ_Z1);
+		break;
+	case 3:
+		*val = tsc2007_xfer(tsc, READ_Z2);
+		break;
+	case 4:
+		*val = tsc2007_xfer(tsc, (ADC_ON_12BIT | TSC2007_MEASURE_AUX));
+		break;
+	case 5: {
+		struct ts_event tc;
+
+		tc.x = tsc2007_xfer(tsc, READ_X);
+		tc.z1 = tsc2007_xfer(tsc, READ_Z1);
+		tc.z2 = tsc2007_xfer(tsc, READ_Z2);
+		*val = tsc2007_calculate_pressure(tsc, &tc);
+		break;
+	}
+	case 6:
+		*val = tsc2007_is_pen_down(tsc);
+		break;
+	case 7:
+		*val = tsc2007_xfer(tsc,
+				    (ADC_ON_12BIT | TSC2007_MEASURE_TEMP0));
+		break;
+	case 8:
+		*val = tsc2007_xfer(tsc,
+				    (ADC_ON_12BIT | TSC2007_MEASURE_TEMP1));
+		break;
+	}
+
+	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
+	tsc2007_xfer(tsc, PWRDOWN);
+
+	mutex_unlock(&tsc->mlock);
+
+	ret = IIO_VAL_INT;
+
+	return ret;
+}
+
+static const struct iio_info tsc2007_iio_info = {
+	.read_raw = tsc2007_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+int tsc2007_iio_configure(struct tsc2007 *ts)
+{
+	struct iio_dev *indio_dev;
+	struct tsc2007_iio *iio;
+	int error;
+
+	indio_dev = devm_iio_device_alloc(&ts->client->dev, sizeof(*iio));
+	if (!indio_dev) {
+		dev_err(&ts->client->dev, "iio_device_alloc failed\n");
+		return -ENOMEM;
+	}
+
+	iio = iio_priv(indio_dev);
+	iio->ts = ts;
+
+	indio_dev->name = "tsc2007";
+	indio_dev->dev.parent = &ts->client->dev;
+	indio_dev->info = &tsc2007_iio_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = tsc2007_iio_channel;
+	indio_dev->num_channels = ARRAY_SIZE(tsc2007_iio_channel);
+
+	error = devm_iio_device_register(&ts->client->dev, indio_dev);
+	if (error) {
+		dev_err(&ts->client->dev,
+			"iio_device_register() failed: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}