HID: i2c-hid: Introduce goodix-i2c-hid using i2c-hid core

Goodix i2c-hid touchscreens are mostly i2c-hid compliant but have some
special power sequencing requirements, including the need to drive a
reset line during the sequencing.

Let's use the new rejiggering of i2c-hid to support this with a thin
wrapper driver to support the first Goodix i2c-hid touchscreen:
GT7375P

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/i2c-hid/Kconfig

@@ -32,10 +32,25 @@ config I2C_HID_OF
 	  will be called i2c-hid-of.  It will also build/depend on the
 	  module i2c-hid.
 
+config I2C_HID_OF_GOODIX
+	tristate "Driver for Goodix hid-i2c based devices on OF systems"
+	default n
+	depends on I2C && INPUT && OF
+	help
+	  Say Y here if you want support for Goodix i2c devices that use
+	  the i2c-hid protocol on Open Firmware (Device Tree)-based
+	  systems.
+
+	  If unsure, say N.
+
+	  This support is also available as a module.  If so, the module
+	  will be called i2c-hid-of-goodix.  It will also build/depend on
+	  the module i2c-hid.
+
 endmenu
 
 config I2C_HID_CORE
 	tristate
-	default y if I2C_HID_ACPI=y || I2C_HID_OF=y
-	default m if I2C_HID_ACPI=m || I2C_HID_OF=m
+	default y if I2C_HID_ACPI=y || I2C_HID_OF=y || I2C_HID_OF_GOODIX=y
+	default m if I2C_HID_ACPI=m || I2C_HID_OF=m || I2C_HID_OF_GOODIX=m
 	select HID

drivers/hid/i2c-hid/Makefile

@@ -10,3 +10,4 @@ i2c-hid-$(CONFIG_DMI)				+= i2c-hid-dmi-quirks.o
 
 obj-$(CONFIG_I2C_HID_ACPI)			+= i2c-hid-acpi.o
 obj-$(CONFIG_I2C_HID_OF)			+= i2c-hid-of.o
+obj-$(CONFIG_I2C_HID_OF_GOODIX)			+= i2c-hid-of-goodix.o

drivers/hid/i2c-hid/i2c-hid-of-goodix.c

@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Goodix touchscreens that use the i2c-hid protocol.
+ *
+ * Copyright 2020 Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
+
+#include "i2c-hid.h"
+
+struct goodix_i2c_hid_timing_data {
+	unsigned int post_gpio_reset_delay_ms;
+	unsigned int post_power_delay_ms;
+};
+
+struct i2c_hid_of_goodix {
+	struct i2chid_ops ops;
+
+	struct regulator *vdd;
+	struct gpio_desc *reset_gpio;
+	const struct goodix_i2c_hid_timing_data *timings;
+};
+
+static int goodix_i2c_hid_power_up(struct i2chid_ops *ops)
+{
+	struct i2c_hid_of_goodix *ihid_goodix =
+		container_of(ops, struct i2c_hid_of_goodix, ops);
+	int ret;
+
+	ret = regulator_enable(ihid_goodix->vdd);
+	if (ret)
+		return ret;
+
+	if (ihid_goodix->timings->post_power_delay_ms)
+		msleep(ihid_goodix->timings->post_power_delay_ms);
+
+	gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 0);
+	if (ihid_goodix->timings->post_gpio_reset_delay_ms)
+		msleep(ihid_goodix->timings->post_gpio_reset_delay_ms);
+
+	return 0;
+}
+
+static void goodix_i2c_hid_power_down(struct i2chid_ops *ops)
+{
+	struct i2c_hid_of_goodix *ihid_goodix =
+		container_of(ops, struct i2c_hid_of_goodix, ops);
+
+	gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
+	regulator_disable(ihid_goodix->vdd);
+}
+
+static int i2c_hid_of_goodix_probe(struct i2c_client *client,
+				   const struct i2c_device_id *id)
+{
+	struct i2c_hid_of_goodix *ihid_goodix;
+
+	ihid_goodix = devm_kzalloc(&client->dev, sizeof(*ihid_goodix),
+				   GFP_KERNEL);
+	if (!ihid_goodix)
+		return -ENOMEM;
+
+	ihid_goodix->ops.power_up = goodix_i2c_hid_power_up;
+	ihid_goodix->ops.power_down = goodix_i2c_hid_power_down;
+
+	/* Start out with reset asserted */
+	ihid_goodix->reset_gpio =
+		devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ihid_goodix->reset_gpio))
+		return PTR_ERR(ihid_goodix->reset_gpio);
+
+	ihid_goodix->vdd = devm_regulator_get(&client->dev, "vdd");
+	if (IS_ERR(ihid_goodix->vdd))
+		return PTR_ERR(ihid_goodix->vdd);
+
+	ihid_goodix->timings = device_get_match_data(&client->dev);
+
+	return i2c_hid_core_probe(client, &ihid_goodix->ops, 0x0001);
+}
+
+static const struct goodix_i2c_hid_timing_data goodix_gt7375p_timing_data = {
+	.post_power_delay_ms = 10,
+	.post_gpio_reset_delay_ms = 180,
+};
+
+static const struct of_device_id goodix_i2c_hid_of_match[] = {
+	{ .compatible = "goodix,gt7375p", .data = &goodix_gt7375p_timing_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, goodix_i2c_hid_of_match);
+
+static struct i2c_driver goodix_i2c_hid_ts_driver = {
+	.driver = {
+		.name	= "i2c_hid_of_goodix",
+		.pm	= &i2c_hid_core_pm,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(goodix_i2c_hid_of_match),
+	},
+	.probe		= i2c_hid_of_goodix_probe,
+	.remove		= i2c_hid_core_remove,
+	.shutdown	= i2c_hid_core_shutdown,
+};
+module_i2c_driver(goodix_i2c_hid_ts_driver);
+
+MODULE_AUTHOR("Douglas Anderson <dianders@chromium.org>");
+MODULE_DESCRIPTION("Goodix i2c-hid touchscreen driver");
+MODULE_LICENSE("GPL v2");