Input: Add touchscreen support for Colibri VF50

The Colibri Vybrid VF50 module supports 4-wire touchscreens using
FETs and ADC inputs. This driver uses the IIO consumer interface
and relies on the vf610_adc driver based on the IIO framework.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

4 files changed, 435 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt b/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt
new file mode 100644
index 000000000000..9d9e930f3251
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt
@@ -0,0 +1,36 @@
+* Toradex Colibri VF50 Touchscreen driver
+
+Required Properties:
+- compatible must be toradex,vf50-touchscreen
+- io-channels: adc channels being used by the Colibri VF50 module
+- xp-gpios: FET gate driver for input of X+
+- xm-gpios: FET gate driver for input of X-
+- yp-gpios: FET gate driver for input of Y+
+- ym-gpios: FET gate driver for input of Y-
+- interrupt-parent: phandle for the interrupt controller
+- interrupts: pen irq interrupt for touch detection
+- pinctrl-names: "idle", "default", "gpios"
+- pinctrl-0: pinctrl node for pen/touch detection state pinmux
+- pinctrl-1: pinctrl node for X/Y and pressure measurement (ADC) state pinmux
+- pinctrl-2: pinctrl node for gpios functioning as FET gate drivers
+- vf50-ts-min-pressure: pressure level at which to stop measuring X/Y values
+
+Example:
+
+        touchctrl: vf50_touchctrl {
+                compatible = "toradex,vf50-touchscreen";
+                io-channels = <&adc1 0>,<&adc0 0>,
+                                <&adc0 1>,<&adc1 2>;
+                xp-gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;
+                xm-gpios = <&gpio2 29 GPIO_ACTIVE_HIGH>;
+                yp-gpios = <&gpio0 12 GPIO_ACTIVE_LOW>;
+                ym-gpios = <&gpio0 4 GPIO_ACTIVE_HIGH>;
+                interrupt-parent = <&gpio0>;
+                interrupts = <8 IRQ_TYPE_LEVEL_LOW>;
+                pinctrl-names = "idle","default","gpios";
+                pinctrl-0 = <&pinctrl_touchctrl_idle>;
+                pinctrl-1 = <&pinctrl_touchctrl_default>;
+                pinctrl-2 = <&pinctrl_touchctrl_gpios>;
+                vf50-ts-min-pressure = <200>;
+                status = "disabled";
+        };
diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index 059edeb7f04a..a6d7a4d8dbb7 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -1040,4 +1040,16 @@ config TOUCHSCREEN_ZFORCE
           To compile this driver as a module, choose M here: the
           module will be called zforce_ts.
 
+config TOUCHSCREEN_COLIBRI_VF50
+        tristate "Toradex Colibri on board touchscreen driver"
+        depends on GPIOLIB && IIO && VF610_ADC
+        help
+          Say Y here if you have a Colibri VF50 and plan to use
+          the on-board provided 4-wire touchscreen driver.
+
+          If unsure, say N.
+
+          To compile this driver as a module, choose M here: the
+          module will be called colibri_vf50_ts.
+
 endif
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index c85aae23e7f8..fb27f7e36070 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -85,3 +85,4 @@ obj-$(CONFIG_TOUCHSCREEN_W90X900)	+= w90p910_ts.o
 obj-$(CONFIG_TOUCHSCREEN_SX8654)        += sx8654.o
 obj-$(CONFIG_TOUCHSCREEN_TPS6507X)      += tps6507x-ts.o
 obj-$(CONFIG_TOUCHSCREEN_ZFORCE)        += zforce_ts.o
+obj-$(CONFIG_TOUCHSCREEN_COLIBRI_VF50)  += colibri-vf50-ts.o
diff --git a/drivers/input/touchscreen/colibri-vf50-ts.c b/drivers/input/touchscreen/colibri-vf50-ts.c
new file mode 100644
index 000000000000..5d4903a402cc
--- /dev/null
+++ b/drivers/input/touchscreen/colibri-vf50-ts.c
@@ -0,0 +1,386 @@
+/*
+ * Toradex Colibri VF50 Touchscreen driver
+ *
+ * Copyright 2015 Toradex AG
+ *
+ * Originally authored by Stefan Agner for 3.0 kernel
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/types.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define DRIVER_NAME                     "colibri-vf50-ts"
+#define DRV_VERSION                     "1.0"
+
+#define VF_ADC_MAX                      ((1 << 12) - 1)
+
+#define COLI_TOUCH_MIN_DELAY_US         1000
+#define COLI_TOUCH_MAX_DELAY_US         2000
+#define COLI_PULLUP_MIN_DELAY_US        10000
+#define COLI_PULLUP_MAX_DELAY_US        11000
+#define COLI_TOUCH_NO_OF_AVGS           5
+#define COLI_TOUCH_REQ_ADC_CHAN         4
+
+struct vf50_touch_device {
+        struct platform_device *pdev;
+        struct input_dev *ts_input;
+        struct iio_channel *channels;
+        struct gpio_desc *gpio_xp;
+        struct gpio_desc *gpio_xm;
+        struct gpio_desc *gpio_yp;
+        struct gpio_desc *gpio_ym;
+        int pen_irq;
+        int min_pressure;
+        bool stop_touchscreen;
+};
+
+/*
+ * Enables given plates and measures touch parameters using ADC
+ */
+static int adc_ts_measure(struct iio_channel *channel,
+                          struct gpio_desc *plate_p, struct gpio_desc *plate_m)
+{
+        int i, value = 0, val = 0;
+        int error;
+
+        gpiod_set_value(plate_p, 1);
+        gpiod_set_value(plate_m, 1);
+
+        usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
+
+        for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
+                error = iio_read_channel_raw(channel, &val);
+                if (error < 0) {
+                        value = error;
+                        goto error_iio_read;
+                }
+
+                value += val;
+        }
+
+        value /= COLI_TOUCH_NO_OF_AVGS;
+
+error_iio_read:
+        gpiod_set_value(plate_p, 0);
+        gpiod_set_value(plate_m, 0);
+
+        return value;
+}
+
+/*
+ * Enable touch detection using falling edge detection on XM
+ */
+static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
+{
+        /* Enable plate YM (needs to be strong GND, high active) */
+        gpiod_set_value(vf50_ts->gpio_ym, 1);
+
+        /*
+         * Let the platform mux to idle state in order to enable
+         * Pull-Up on GPIO
+         */
+        pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
+
+        /* Wait for the pull-up to be stable on high */
+        usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
+}
+
+/*
+ * ADC touch screen sampling bottom half irq handler
+ */
+static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
+{
+        struct vf50_touch_device *vf50_ts = private;
+        struct device *dev = &vf50_ts->pdev->dev;
+        int val_x, val_y, val_z1, val_z2, val_p = 0;
+        bool discard_val_on_start = true;
+
+        /* Disable the touch detection plates */
+        gpiod_set_value(vf50_ts->gpio_ym, 0);
+
+        /* Let the platform mux to default state in order to mux as ADC */
+        pinctrl_pm_select_default_state(dev);
+
+        while (!vf50_ts->stop_touchscreen) {
+                /* X-Direction */
+                val_x = adc_ts_measure(&vf50_ts->channels[0],
+                                vf50_ts->gpio_xp, vf50_ts->gpio_xm);
+                if (val_x < 0)
+                        break;
+
+                /* Y-Direction */
+                val_y = adc_ts_measure(&vf50_ts->channels[1],
+                                vf50_ts->gpio_yp, vf50_ts->gpio_ym);
+                if (val_y < 0)
+                        break;
+
+                /*
+                 * Touch pressure
+                 * Measure on XP/YM
+                 */
+                val_z1 = adc_ts_measure(&vf50_ts->channels[2],
+                                vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+                if (val_z1 < 0)
+                        break;
+                val_z2 = adc_ts_measure(&vf50_ts->channels[3],
+                                vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+                if (val_z2 < 0)
+                        break;
+
+                /* Validate signal (avoid calculation using noise) */
+                if (val_z1 > 64 && val_x > 64) {
+                        /*
+                         * Calculate resistance between the plates
+                         * lower resistance means higher pressure
+                         */
+                        int r_x = (1000 * val_x) / VF_ADC_MAX;
+
+                        val_p = (r_x * val_z2) / val_z1 - r_x;
+
+                } else {
+                        val_p = 2000;
+                }
+
+                val_p = 2000 - val_p;
+                dev_dbg(dev,
+                        "Measured values: x: %d, y: %d, z1: %d, z2: %d, p: %d\n",
+                        val_x, val_y, val_z1, val_z2, val_p);
+
+                /*
+                 * If touch pressure is too low, stop measuring and reenable
+                 * touch detection
+                 */
+                if (val_p < vf50_ts->min_pressure || val_p > 2000)
+                        break;
+
+                /*
+                 * The pressure may not be enough for the first x and the
+                 * second y measurement, but, the pressure is ok when the
+                 * driver is doing the third and fourth measurement. To
+                 * take care of this, we drop the first measurement always.
+                 */
+                if (discard_val_on_start) {
+                        discard_val_on_start = false;
+                } else {
+                        /*
+                         * Report touch position and sleep for
+                         * the next measurement.
+                         */
+                        input_report_abs(vf50_ts->ts_input,
+                                        ABS_X, VF_ADC_MAX - val_x);
+                        input_report_abs(vf50_ts->ts_input,
+                                        ABS_Y, VF_ADC_MAX - val_y);
+                        input_report_abs(vf50_ts->ts_input,
+                                        ABS_PRESSURE, val_p);
+                        input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
+                        input_sync(vf50_ts->ts_input);
+                }
+
+                usleep_range(COLI_PULLUP_MIN_DELAY_US,
+                             COLI_PULLUP_MAX_DELAY_US);
+        }
+
+        /* Report no more touch, re-enable touch detection */
+        input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
+        input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
+        input_sync(vf50_ts->ts_input);
+
+        vf50_ts_enable_touch_detection(vf50_ts);
+
+        return IRQ_HANDLED;
+}
+
+static int vf50_ts_open(struct input_dev *dev_input)
+{
+        struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
+        struct device *dev = &touchdev->pdev->dev;
+
+        dev_dbg(dev, "Input device %s opened, starting touch detection\n",
+                dev_input->name);
+
+        touchdev->stop_touchscreen = false;
+
+        /* Mux detection before request IRQ, wait for pull-up to settle */
+        vf50_ts_enable_touch_detection(touchdev);
+
+        return 0;
+}
+
+static void vf50_ts_close(struct input_dev *dev_input)
+{
+        struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
+        struct device *dev = &touchdev->pdev->dev;
+
+        touchdev->stop_touchscreen = true;
+
+        /* Make sure IRQ is not running past close */
+        mb();
+        synchronize_irq(touchdev->pen_irq);
+
+        gpiod_set_value(touchdev->gpio_ym, 0);
+        pinctrl_pm_select_default_state(dev);
+
+        dev_dbg(dev, "Input device %s closed, disable touch detection\n",
+                dev_input->name);
+}
+
+static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
+                             const char *con_id, enum gpiod_flags flags)
+{
+        int error;
+
+        *gpio_d = devm_gpiod_get(dev, con_id, flags);
+        if (IS_ERR(*gpio_d)) {
+                error = PTR_ERR(*gpio_d);
+                dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
+                return error;
+        }
+
+        return 0;
+}
+
+static void vf50_ts_channel_release(void *data)
+{
+        struct iio_channel *channels = data;
+
+        iio_channel_release_all(channels);
+}
+
+static int vf50_ts_probe(struct platform_device *pdev)
+{
+        struct input_dev *input;
+        struct iio_channel *channels;
+        struct device *dev = &pdev->dev;
+        struct vf50_touch_device *touchdev;
+        int num_adc_channels;
+        int error;
+
+        channels = iio_channel_get_all(dev);
+        if (IS_ERR(channels))
+                return PTR_ERR(channels);
+
+        error = devm_add_action(dev, vf50_ts_channel_release, channels);
+        if (error) {
+                iio_channel_release_all(channels);
+                dev_err(dev, "Failed to register iio channel release action");
+                return error;
+        }
+
+        num_adc_channels = 0;
+        while (channels[num_adc_channels].indio_dev)
+                num_adc_channels++;
+
+        if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
+                dev_err(dev, "Inadequate ADC channels specified\n");
+                return -EINVAL;
+        }
+
+        touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
+        if (!touchdev)
+                return -ENOMEM;
+
+        touchdev->pdev = pdev;
+        touchdev->channels = channels;
+
+        error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
+                                 &touchdev->min_pressure);
+        if (error)
+                return error;
+
+        input = devm_input_allocate_device(dev);
+        if (!input) {
+                dev_err(dev, "Failed to allocate TS input device\n");
+                return -ENOMEM;
+        }
+
+        platform_set_drvdata(pdev, touchdev);
+
+        input->name = DRIVER_NAME;
+        input->id.bustype = BUS_HOST;
+        input->dev.parent = dev;
+        input->open = vf50_ts_open;
+        input->close = vf50_ts_close;
+
+        input_set_capability(input, EV_KEY, BTN_TOUCH);
+        input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
+        input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
+        input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
+
+        touchdev->ts_input = input;
+        input_set_drvdata(input, touchdev);
+
+        error = input_register_device(input);
+        if (error) {
+                dev_err(dev, "Failed to register input device\n");
+                return error;
+        }
+
+        error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
+        if (error)
+                return error;
+
+        error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
+                                "xm", GPIOD_OUT_LOW);
+        if (error)
+                return error;
+
+        error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
+        if (error)
+                return error;
+
+        error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
+        if (error)
+                return error;
+
+        touchdev->pen_irq = platform_get_irq(pdev, 0);
+        if (touchdev->pen_irq < 0)
+                return touchdev->pen_irq;
+
+        error = devm_request_threaded_irq(dev, touchdev->pen_irq,
+                                          NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
+                                          "vf50 touch", touchdev);
+        if (error) {
+                dev_err(dev, "Failed to request IRQ %d: %d\n",
+                        touchdev->pen_irq, error);
+                return error;
+        }
+
+        return 0;
+}
+
+static const struct of_device_id vf50_touch_of_match[] = {
+        { .compatible = "toradex,vf50-touchscreen", },
+        { }
+};
+MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
+
+static struct platform_driver vf50_touch_driver = {
+        .driver = {
+                .name = "toradex,vf50_touchctrl",
+                .of_match_table = vf50_touch_of_match,
+        },
+        .probe = vf50_ts_probe,
+};
+module_platform_driver(vf50_touch_driver);
+
+MODULE_AUTHOR("Sanchayan Maity");
+MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);