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 <hns@goldelico.com>
Reviewed-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 457 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/tsc2007_core.c b/drivers/input/touchscreen/tsc2007_core.c
new file mode 100644
index 000000000000..fdf81a2b989a
--- /dev/null
+++ b/drivers/input/touchscreen/tsc2007_core.c
@@ -0,0 +1,457 @@
+/*
+ * drivers/input/touchscreen/tsc2007.c
+ *
+ * Copyright (c) 2008 MtekVision Co., Ltd.
+ *	Kwangwoo Lee <kwlee@mtekvision.com>
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/i2c/tsc2007.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include "tsc2007.h"
+
+int tsc2007_xfer(struct tsc2007 *tsc, u8 cmd)
+{
+	s32 data;
+	u16 val;
+
+	data = i2c_smbus_read_word_data(tsc->client, cmd);
+	if (data < 0) {
+		dev_err(&tsc->client->dev, "i2c io error: %d\n", data);
+		return data;
+	}
+
+	/* The protocol and raw data format from i2c interface:
+	 * S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
+	 * Where DataLow has [D11-D4], DataHigh has [D3-D0 << 4 | Dummy 4bit].
+	 */
+	val = swab16(data) >> 4;
+
+	dev_dbg(&tsc->client->dev, "data: 0x%x, val: 0x%x\n", data, val);
+
+	return val;
+}
+
+static void tsc2007_read_values(struct tsc2007 *tsc, struct ts_event *tc)
+{
+	/* y- still on; turn on only y+ (and ADC) */
+	tc->y = tsc2007_xfer(tsc, READ_Y);
+
+	/* turn y- off, x+ on, then leave in lowpower */
+	tc->x = tsc2007_xfer(tsc, READ_X);
+
+	/* turn y+ off, x- on; we'll use formula #1 */
+	tc->z1 = tsc2007_xfer(tsc, READ_Z1);
+	tc->z2 = tsc2007_xfer(tsc, READ_Z2);
+
+	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
+	tsc2007_xfer(tsc, PWRDOWN);
+}
+
+u32 tsc2007_calculate_pressure(struct tsc2007 *tsc, struct ts_event *tc)
+{
+	u32 rt = 0;
+
+	/* range filtering */
+	if (tc->x == MAX_12BIT)
+		tc->x = 0;
+
+	if (likely(tc->x && tc->z1)) {
+		/* compute touch pressure resistance using equation #1 */
+		rt = tc->z2 - tc->z1;
+		rt *= tc->x;
+		rt *= tsc->x_plate_ohms;
+		rt /= tc->z1;
+		rt = (rt + 2047) >> 12;
+	}
+
+	return rt;
+}
+
+bool tsc2007_is_pen_down(struct tsc2007 *ts)
+{
+	/*
+	 * NOTE: We can't rely on the pressure to determine the pen down
+	 * state, even though 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
+	 * work function by reading the pen signal state (it's a GPIO
+	 * and IRQ). Unfortunately such callback is not always available,
+	 * in that case we assume that the pen is down and expect caller
+	 * to fall back on the pressure reading.
+	 */
+
+	if (!ts->get_pendown_state)
+		return true;
+
+	return ts->get_pendown_state(&ts->client->dev);
+}
+
+static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
+{
+	struct tsc2007 *ts = handle;
+	struct input_dev *input = ts->input;
+	struct ts_event tc;
+	u32 rt;
+
+	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);
+
+		if (!rt && !ts->get_pendown_state) {
+			/*
+			 * If pressure reported is 0 and we don't have
+			 * callback to check pendown state, we have to
+			 * assume that pen was lifted up.
+			 */
+			break;
+		}
+
+		if (rt <= ts->max_rt) {
+			dev_dbg(&ts->client->dev,
+				"DOWN point(%4d,%4d), pressure (%4u)\n",
+				tc.x, tc.y, rt);
+
+			input_report_key(input, BTN_TOUCH, 1);
+			input_report_abs(input, ABS_X, tc.x);
+			input_report_abs(input, ABS_Y, tc.y);
+			input_report_abs(input, ABS_PRESSURE, rt);
+
+			input_sync(input);
+
+		} else {
+			/*
+			 * 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.
+			 */
+			dev_dbg(&ts->client->dev, "ignored pressure %d\n", rt);
+		}
+
+		wait_event_timeout(ts->wait, ts->stopped, ts->poll_period);
+	}
+
+	dev_dbg(&ts->client->dev, "UP\n");
+
+	input_report_key(input, BTN_TOUCH, 0);
+	input_report_abs(input, ABS_PRESSURE, 0);
+	input_sync(input);
+
+	if (ts->clear_penirq)
+		ts->clear_penirq();
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t tsc2007_hard_irq(int irq, void *handle)
+{
+	struct tsc2007 *ts = handle;
+
+	if (tsc2007_is_pen_down(ts))
+		return IRQ_WAKE_THREAD;
+
+	if (ts->clear_penirq)
+		ts->clear_penirq();
+
+	return IRQ_HANDLED;
+}
+
+static void tsc2007_stop(struct tsc2007 *ts)
+{
+	ts->stopped = true;
+	mb();
+	wake_up(&ts->wait);
+
+	disable_irq(ts->irq);
+}
+
+static int tsc2007_open(struct input_dev *input_dev)
+{
+	struct tsc2007 *ts = input_get_drvdata(input_dev);
+	int err;
+
+	ts->stopped = false;
+	mb();
+
+	enable_irq(ts->irq);
+
+	/* Prepare for touch readings - power down ADC and enable PENIRQ */
+	err = tsc2007_xfer(ts, PWRDOWN);
+	if (err < 0) {
+		tsc2007_stop(ts);
+		return err;
+	}
+
+	return 0;
+}
+
+static void tsc2007_close(struct input_dev *input_dev)
+{
+	struct tsc2007 *ts = input_get_drvdata(input_dev);
+
+	tsc2007_stop(ts);
+}
+
+#ifdef CONFIG_OF
+static int tsc2007_get_pendown_state_gpio(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct tsc2007 *ts = i2c_get_clientdata(client);
+
+	return !gpio_get_value(ts->gpio);
+}
+
+static int tsc2007_probe_dt(struct i2c_client *client, struct tsc2007 *ts)
+{
+	struct device_node *np = client->dev.of_node;
+	u32 val32;
+	u64 val64;
+
+	if (!np) {
+		dev_err(&client->dev, "missing device tree data\n");
+		return -EINVAL;
+	}
+
+	if (!of_property_read_u32(np, "ti,max-rt", &val32))
+		ts->max_rt = val32;
+	else
+		ts->max_rt = MAX_12BIT;
+
+	if (!of_property_read_u32(np, "ti,fuzzx", &val32))
+		ts->fuzzx = val32;
+
+	if (!of_property_read_u32(np, "ti,fuzzy", &val32))
+		ts->fuzzy = val32;
+
+	if (!of_property_read_u32(np, "ti,fuzzz", &val32))
+		ts->fuzzz = val32;
+
+	if (!of_property_read_u64(np, "ti,poll-period", &val64))
+		ts->poll_period = msecs_to_jiffies(val64);
+	else
+		ts->poll_period = msecs_to_jiffies(1);
+
+	if (!of_property_read_u32(np, "ti,x-plate-ohms", &val32)) {
+		ts->x_plate_ohms = val32;
+	} else {
+		dev_err(&client->dev, "missing ti,x-plate-ohms devicetree property.");
+		return -EINVAL;
+	}
+
+	ts->gpio = of_get_gpio(np, 0);
+	if (gpio_is_valid(ts->gpio))
+		ts->get_pendown_state = tsc2007_get_pendown_state_gpio;
+	else
+		dev_warn(&client->dev,
+			 "GPIO not specified in DT (of_get_gpio returned %d)\n",
+			 ts->gpio);
+
+	return 0;
+}
+#else
+static int tsc2007_probe_dt(struct i2c_client *client, struct tsc2007 *ts)
+{
+	dev_err(&client->dev, "platform data is required!\n");
+	return -EINVAL;
+}
+#endif
+
+static int tsc2007_probe_pdev(struct i2c_client *client, struct tsc2007 *ts,
+			      const struct tsc2007_platform_data *pdata,
+			      const struct i2c_device_id *id)
+{
+	ts->model             = pdata->model;
+	ts->x_plate_ohms      = pdata->x_plate_ohms;
+	ts->max_rt            = pdata->max_rt ? : MAX_12BIT;
+	ts->poll_period       = msecs_to_jiffies(pdata->poll_period ? : 1);
+	ts->get_pendown_state = pdata->get_pendown_state;
+	ts->clear_penirq      = pdata->clear_penirq;
+	ts->fuzzx             = pdata->fuzzx;
+	ts->fuzzy             = pdata->fuzzy;
+	ts->fuzzz             = pdata->fuzzz;
+
+	if (pdata->x_plate_ohms == 0) {
+		dev_err(&client->dev, "x_plate_ohms is not set up in platform data");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void tsc2007_call_exit_platform_hw(void *data)
+{
+	struct device *dev = data;
+	const struct tsc2007_platform_data *pdata = dev_get_platdata(dev);
+
+	pdata->exit_platform_hw();
+}
+
+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);
+	struct tsc2007 *ts;
+	struct input_dev *input_dev;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -EIO;
+
+	ts = devm_kzalloc(&client->dev, sizeof(struct tsc2007), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	if (pdata)
+		err = tsc2007_probe_pdev(client, ts, pdata, id);
+	else
+		err = tsc2007_probe_dt(client, ts);
+	if (err)
+		return err;
+
+	input_dev = devm_input_allocate_device(&client->dev);
+	if (!input_dev)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, ts);
+
+	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));
+
+	input_dev->name = "TSC2007 Touchscreen";
+	input_dev->phys = ts->phys;
+	input_dev->id.bustype = BUS_I2C;
+
+	input_dev->open = tsc2007_open;
+	input_dev->close = tsc2007_close;
+
+	input_set_drvdata(input_dev, ts);
+
+	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, 0, MAX_12BIT, ts->fuzzx, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, MAX_12BIT, ts->fuzzy, 0);
+	input_set_abs_params(input_dev, ABS_PRESSURE, 0, MAX_12BIT,
+			     ts->fuzzz, 0);
+
+	if (pdata) {
+		if (pdata->exit_platform_hw) {
+			err = devm_add_action(&client->dev,
+					      tsc2007_call_exit_platform_hw,
+					      &client->dev);
+			if (err) {
+				dev_err(&client->dev,
+					"Failed to register exit_platform_hw action, %d\n",
+					err);
+				return err;
+			}
+		}
+
+		if (pdata->init_platform_hw)
+			pdata->init_platform_hw();
+	}
+
+	err = devm_request_threaded_irq(&client->dev, ts->irq,
+					tsc2007_hard_irq, tsc2007_soft_irq,
+					IRQF_ONESHOT,
+					client->dev.driver->name, ts);
+	if (err) {
+		dev_err(&client->dev, "Failed to request irq %d: %d\n",
+			ts->irq, err);
+		return err;
+	}
+
+	tsc2007_stop(ts);
+
+	/* power down the chip (TSC2007_SETUP does not ACK on I2C) */
+	err = tsc2007_xfer(ts, PWRDOWN);
+	if (err < 0) {
+		dev_err(&client->dev,
+			"Failed to setup chip: %d\n", err);
+		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;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id tsc2007_idtable[] = {
+	{ "tsc2007", 0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, tsc2007_idtable);
+
+#ifdef CONFIG_OF
+static const struct of_device_id tsc2007_of_match[] = {
+	{ .compatible = "ti,tsc2007" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, tsc2007_of_match);
+#endif
+
+static struct i2c_driver tsc2007_driver = {
+	.driver = {
+		.name	= "tsc2007",
+		.of_match_table = of_match_ptr(tsc2007_of_match),
+	},
+	.id_table	= tsc2007_idtable,
+	.probe		= tsc2007_probe,
+};
+
+module_i2c_driver(tsc2007_driver);
+
+MODULE_AUTHOR("Kwangwoo Lee <kwlee@mtekvision.com>");
+MODULE_DESCRIPTION("TSC2007 TouchScreen Driver");
+MODULE_LICENSE("GPL");