// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Himax hx83112b touchscreens
 *
 * Copyright (C) 2022 Job Noorman <job@noorman.info>
 *
 * This code is based on "Himax Android Driver Sample Code for QCT platform":
 *
 * Copyright (C) 2017 Himax Corporation.
 */

#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

#define HIMAX_INVALID_COORD		0xffff

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;

	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;

	error = regmap_read(ts->regmap, HIMAX_REG_CFG_READ_VALUE, dst);
	if (error)
		return error;

	return 0;
}

static void himax_reset(struct himax_ts_data *ts)
{
	gpiod_set_value_cansleep(ts->gpiod_rst, 1);

	/* Delay copied from downstream driver */
	msleep(20);
	gpiod_set_value_cansleep(ts->gpiod_rst, 0);

	/*
	 * The downstream driver doesn't contain this delay but is seems safer
	 * to include it. The range is just a guess that seems to work well.
	 */
	usleep_range(1000, 1100);
}

static int himax_read_product_id(struct himax_ts_data *ts, u32 *product_id)
{
	int error;

	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:
		dev_err(&ts->client->dev,
			"Unknown product id: %x\n", product_id);
		return -EINVAL;
	}
}

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) {
		dev_err(&ts->client->dev, "Failed to allocate input device\n");
		return -ENOMEM;
	}

	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) {
		dev_err(&ts->client->dev,
			"Failed to initialize MT slots: %d\n", error);
		return error;
	}

	error = input_register_device(ts->input_dev);
	if (error) {
		dev_err(&ts->client->dev,
			"Failed to register input device: %d\n", error);
		return error;
	}

	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_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 = be16_to_cpu(point->x);
	u16 y = be16_to_cpu(point->y);
	u8 w = event->majors[point_index];

	if (x == HIMAX_INVALID_COORD || y == HIMAX_INVALID_COORD)
		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 int himax_handle_input(struct himax_ts_data *ts)
{
	int error;
	struct himax_event event;

	error = regmap_raw_read(ts->regmap, HIMAX_REG_READ_EVENT, &event,
				sizeof(event));
	if (error) {
		dev_err(&ts->client->dev, "Failed to read input event: %d\n",
			error);
		return error;
	}

	/*
	 * Only process the current event when it has a valid checksum but
	 * don't consider it a fatal error when it doesn't.
	 */
	if (himax_verify_checksum(ts, &event))
		himax_process_event(ts, &event);

	return 0;
}

static irqreturn_t himax_irq_handler(int irq, void *dev_id)
{
	int error;
	struct himax_ts_data *ts = dev_id;

	error = himax_handle_input(ts);
	if (error)
		return IRQ_NONE;

	return IRQ_HANDLED;
}

static int himax_probe(struct i2c_client *client)
{
	int error;
	struct device *dev = &client->dev;
	struct himax_ts_data *ts;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
		dev_err(dev, "I2C check functionality failed\n");
		return -ENXIO;
	}

	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);
	error = PTR_ERR_OR_ZERO(ts->regmap);
	if (error) {
		dev_err(dev, "Failed to initialize regmap: %d\n", error);
		return error;
	}

	ts->gpiod_rst = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
	error = PTR_ERR_OR_ZERO(ts->gpiod_rst);
	if (error) {
		dev_err(dev, "Failed to get reset GPIO: %d\n", 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 = devm_request_threaded_irq(dev, client->irq, NULL,
					  himax_irq_handler, IRQF_ONESHOT,
					  client->name, 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 DEFINE_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_new = himax_probe,
	.id_table = himax_ts_id,
	.driver = {
		.name = "Himax-hx83112b-TS",
		.of_match_table = of_match_ptr(himax_of_match),
		.pm = pm_sleep_ptr(&himax_pm_ops),
	},
};
module_i2c_driver(himax_ts_driver);

MODULE_AUTHOR("Job Noorman <job@noorman.info>");
MODULE_DESCRIPTION("Himax hx83112b touchscreen driver");
MODULE_LICENSE("GPL");