[PATCH 2/3] Input: add driver for Himax hx83112b touchscreen devices

[Job Noorman]

This patch adds support for Himax hx83112b touchscreen devices. As there
are no publicly available data sheets for these devices, the
implementation is based on the driver of the downstream Android kernel
used in the Fairphone 3. This patch is a complete rewrite, though, and
the code bears no resemblence to the original implementation.

The driver has been tested on the aforementioned phone.

Signed-off-by: Job Noorman <job@xxxxxxxxxxxx>
---
 MAINTAINERS                                |   1 +
 drivers/input/touchscreen/Kconfig          |  11 +
 drivers/input/touchscreen/Makefile         |   1 +
 drivers/input/touchscreen/himax_hx83112b.c | 376 +++++++++++++++++++++
 4 files changed, 389 insertions(+)
 create mode 100644 drivers/input/touchscreen/himax_hx83112b.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 2418bffe9187..51a03f9586f1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9099,6 +9099,7 @@ M:	Job Noorman <job@xxxxxxxxxxxx>
 L:	linux-input@xxxxxxxxxxxxxxx
 S:	Maintained
 F:	Documentation/devicetree/bindings/input/touchscreen/himax,hx83112b.yaml
+F:	drivers/input/touchscreen/himax_hx83112b.c

 HIPPI
 M:	Jes Sorensen <jes@xxxxxxxxxxxxxxxxxx>
diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index dc90a3ea51ee..fd710fd8cd53 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -1379,4 +1379,15 @@ config TOUCHSCREEN_ZINITIX
 	  To compile this driver as a module, choose M here: the
 	  module will be called zinitix.

+config TOUCHSCREEN_HIMAX_HX83112B
+	tristate "Himax hx83112b touchscreen driver"
+	depends on I2C
+	help
+	  Say Y here to enable support for Himax hx83112b touchscreens.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called himax_hx83112b.
+
 endif
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index 557f84fd2075..0f8bf79e01fe 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -116,3 +116,4 @@ obj-$(CONFIG_TOUCHSCREEN_ROHM_BU21023)	+= rohm_bu21023.o
 obj-$(CONFIG_TOUCHSCREEN_RASPBERRYPI_FW)	+= raspberrypi-ts.o
 obj-$(CONFIG_TOUCHSCREEN_IQS5XX)	+= iqs5xx.o
 obj-$(CONFIG_TOUCHSCREEN_ZINITIX)	+= zinitix.o
+obj-$(CONFIG_TOUCHSCREEN_HIMAX_HX83112B)	+= himax_hx83112b.o
diff --git a/drivers/input/touchscreen/himax_hx83112b.c b/drivers/input/touchscreen/himax_hx83112b.c
new file mode 100644
index 000000000000..04494bf1eb2d
--- /dev/null
+++ b/drivers/input/touchscreen/himax_hx83112b.c
@@ -0,0 +1,376 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Himax hx83112b touchscreens
+ *
+ * Copyright (C) 2022 Job Noorman <job@xxxxxxxxxxxx>
+ *
+ * This code is based on "Himax Android Driver Sample Code for QCT platform":
+ *
+ * Copyright (C) 2017 Himax Corporation.
+ */
+
+#include <asm/byteorder.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/regmap.h>
+
+#define HIMAX_ID_83112B 0x83112b
+
+#define HIMAX_MAX_POINTS 10
+
+#define HIMAX_REG_CFG_SET_ADDR 0x00
+#define HIMAX_REG_CFG_INIT_READ 0x0c
+#define HIMAX_REG_CFG_READ_VALUE 0x08
+#define HIMAX_REG_READ_EVENT 0x30
+
+#define HIMAX_CFG_PRODUCT_ID 0x900000d0
+
+struct himax_event_point {
+	__be16 x;
+	__be16 y;
+} __packed;
+
+struct himax_event {
+	struct himax_event_point points[HIMAX_MAX_POINTS];
+	u8 majors[HIMAX_MAX_POINTS];
+	u8 pad0[2];
+	u8 num_points;
+	u8 pad1[2];
+	u8 checksum_fix;
+} __packed;
+
+static_assert(sizeof(struct himax_event) == 56);
+
+struct himax_ts_data {
+	struct gpio_desc *gpiod_rst;
+	struct input_dev *input_dev;
+	struct i2c_client *client;
+	struct regmap *regmap;
+	struct touchscreen_properties props;
+};
+
+static const struct regmap_config himax_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 32,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static int himax_read_config(struct himax_ts_data *ts, u32 address, u32 *dst)
+{
+	int error = 0;
+
+	error = regmap_write(ts->regmap, HIMAX_REG_CFG_SET_ADDR, address);
+	if (error)
+		return error;
+
+	error = regmap_write(ts->regmap, HIMAX_REG_CFG_INIT_READ, 0x0);
+	if (error)
+		return error;
+
+	return regmap_read(ts->regmap, HIMAX_REG_CFG_READ_VALUE, dst);
+}
+
+static int himax_read_input_event(struct himax_ts_data *ts,
+				  struct himax_event *event)
+{
+	return regmap_raw_read(ts->regmap, HIMAX_REG_READ_EVENT, event,
+			       sizeof(*event));
+}
+
+static void himax_reset(struct himax_ts_data *ts)
+{
+	gpiod_set_value(ts->gpiod_rst, 1);
+	msleep(20);
+	gpiod_set_value(ts->gpiod_rst, 0);
+}
+
+static int himax_read_product_id(struct himax_ts_data *ts, u32 *product_id)
+{
+	int error = himax_read_config(ts, HIMAX_CFG_PRODUCT_ID, product_id);
+
+	if (error)
+		return error;
+
+	*product_id >>= 8;
+	return 0;
+}
+
+static int himax_check_product_id(struct himax_ts_data *ts)
+{
+	int error;
+	u32 product_id;
+
+	error = himax_read_product_id(ts, &product_id);
+	if (error)
+		return error;
+
+	dev_dbg(&ts->client->dev, "Product id: %x\n", product_id);
+
+	switch (product_id) {
+	case HIMAX_ID_83112B:
+		return 0;
+
+	default:
+		return dev_err_probe(&ts->client->dev, -ENODEV,
+				     "Unknown product id: %x\n", product_id);
+	}
+}
+
+static int himax_setup_gpio(struct himax_ts_data *ts)
+{
+	ts->gpiod_rst =
+		devm_gpiod_get(&ts->client->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ts->gpiod_rst)) {
+		return dev_err_probe(&ts->client->dev, PTR_ERR(ts->gpiod_rst),
+				     "Failed to get reset GPIO\n");
+	}
+
+	return 0;
+}
+
+static int himax_input_register(struct himax_ts_data *ts)
+{
+	int error;
+
+	ts->input_dev = devm_input_allocate_device(&ts->client->dev);
+	if (!ts->input_dev) {
+		return dev_err_probe(&ts->client->dev, -ENOMEM,
+				     "Failed to allocate input device\n");
+	}
+
+	ts->input_dev->name = "Himax Touchscreen";
+
+	input_set_capability(ts->input_dev, EV_ABS, ABS_MT_POSITION_X);
+	input_set_capability(ts->input_dev, EV_ABS, ABS_MT_POSITION_Y);
+	input_set_abs_params(ts->input_dev, ABS_MT_WIDTH_MAJOR, 0, 200, 0, 0);
+	input_set_abs_params(ts->input_dev, ABS_MT_TOUCH_MAJOR, 0, 200, 0, 0);
+
+	touchscreen_parse_properties(ts->input_dev, true, &ts->props);
+
+	error = input_mt_init_slots(ts->input_dev, HIMAX_MAX_POINTS,
+				    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
+	if (error) {
+		return dev_err_probe(&ts->client->dev, error,
+				     "Failed to initialize MT slots");
+	}
+
+	error = input_register_device(ts->input_dev);
+	if (error) {
+		return dev_err_probe(&ts->client->dev, error,
+				     "Failed to register input device");
+	}
+
+	return 0;
+}
+
+static u8 himax_event_get_num_points(const struct himax_event *event)
+{
+	if (event->num_points == 0xff)
+		return 0;
+	else
+		return event->num_points & 0x0f;
+}
+
+static bool himax_event_point_is_valid(const struct himax_event_point *point)
+{
+	return point->x != 0xffff && point->y != 0xffff;
+}
+
+static u16 himax_event_point_get_x(const struct himax_event_point *point)
+{
+	return be16_to_cpu(point->x);
+}
+
+static u16 himax_event_point_get_y(const struct himax_event_point *point)
+{
+	return be16_to_cpu(point->y);
+}
+
+static bool himax_process_event_point(struct himax_ts_data *ts,
+				      const struct himax_event *event,
+				      int point_index)
+{
+	const struct himax_event_point *point = &event->points[point_index];
+	u16 x = himax_event_point_get_x(point);
+	u16 y = himax_event_point_get_y(point);
+	u8 w = event->majors[point_index];
+
+	if (!himax_event_point_is_valid(point))
+		return false;
+
+	input_mt_slot(ts->input_dev, point_index);
+	input_mt_report_slot_state(ts->input_dev, MT_TOOL_FINGER, true);
+	touchscreen_report_pos(ts->input_dev, &ts->props, x, y, true);
+	input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR, w);
+	input_report_abs(ts->input_dev, ABS_MT_WIDTH_MAJOR, w);
+	return true;
+}
+
+static void himax_process_event(struct himax_ts_data *ts,
+				const struct himax_event *event)
+{
+	int i;
+	int num_points_left = himax_event_get_num_points(event);
+
+	for (i = 0; i < HIMAX_MAX_POINTS && num_points_left > 0; i++) {
+		if (himax_process_event_point(ts, event, i))
+			num_points_left--;
+	}
+
+	input_mt_sync_frame(ts->input_dev);
+	input_sync(ts->input_dev);
+}
+
+static bool himax_verify_checksum(struct himax_ts_data *ts,
+				  const struct himax_event *event)
+{
+	u8 *data = (u8 *)event;
+	int i;
+	u16 checksum = 0;
+
+	for (i = 0; i < sizeof(*event); i++)
+		checksum += data[i];
+
+	if ((checksum & 0x00ff) != 0) {
+		dev_err(&ts->client->dev, "Wrong event checksum: %04x\n",
+			checksum);
+		return false;
+	}
+
+	return true;
+}
+
+static void himax_handle_input(struct himax_ts_data *ts)
+{
+	int error;
+	struct himax_event event;
+
+	error = himax_read_input_event(ts, &event);
+	if (error) {
+		dev_err(&ts->client->dev, "Failed to read input event: %d\n",
+			error);
+		return;
+	}
+
+	if (!himax_verify_checksum(ts, &event))
+		return;
+
+	himax_process_event(ts, &event);
+}
+
+static irqreturn_t himax_irq_handler(int irq, void *dev_id)
+{
+	struct himax_ts_data *ts = dev_id;
+
+	himax_handle_input(ts);
+	return IRQ_HANDLED;
+}
+
+static int himax_request_irq(struct himax_ts_data *ts)
+{
+	struct i2c_client *client = ts->client;
+
+	return devm_request_threaded_irq(&client->dev, client->irq, NULL,
+					 himax_irq_handler, IRQF_ONESHOT,
+					 client->name, ts);
+}
+
+static int himax_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	int error;
+	struct device *dev = &client->dev;
+	struct himax_ts_data *ts;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		return dev_err_probe(dev, -ENODEV,
+				     "I2C check functionality failed\n");
+	}
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, ts);
+	ts->client = client;
+
+	ts->regmap = devm_regmap_init_i2c(client, &himax_regmap_config);
+	if (IS_ERR(ts->regmap)) {
+		return dev_err_probe(&client->dev, PTR_ERR(ts->regmap),
+				     "Failed to initialize regmap");
+	}
+
+	error = himax_setup_gpio(ts);
+	if (error)
+		return error;
+
+	himax_reset(ts);
+
+	error = himax_check_product_id(ts);
+	if (error)
+		return error;
+
+	error = himax_input_register(ts);
+	if (error)
+		return error;
+
+	error = himax_request_irq(ts);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static int himax_suspend(struct device *dev)
+{
+	struct himax_ts_data *ts = dev_get_drvdata(dev);
+
+	disable_irq(ts->client->irq);
+	return 0;
+}
+
+static int himax_resume(struct device *dev)
+{
+	struct himax_ts_data *ts = dev_get_drvdata(dev);
+
+	enable_irq(ts->client->irq);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(himax_pm_ops, himax_suspend, himax_resume);
+
+static const struct i2c_device_id himax_ts_id[] = {
+	{ "hx83112b", 0 },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(i2c, himax_ts_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id himax_of_match[] = {
+	{ .compatible = "himax,hx83112b" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, himax_of_match);
+#endif
+
+static struct i2c_driver himax_ts_driver = {
+	.probe = himax_probe,
+	.id_table = himax_ts_id,
+	.driver = {
+		.name = "Himax-hx83112b-TS",
+		.of_match_table = of_match_ptr(himax_of_match),
+		.pm = &himax_pm_ops,
+	},
+};
+module_i2c_driver(himax_ts_driver);
+
+MODULE_AUTHOR("Job Noorman <job@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Himax hx83112b touchscreen driver");
+MODULE_LICENSE("GPL");
--
2.38.0