[PATCH v1] regulator: Add Waveshare panel regulator driver

[Sudarshan Shetty <tessolveupstream@gmail.com>]

This patch adds a regulator driver for Waveshare panels.
The regulator provides controlled power sequencing and is also used
to enable or disable the display backlight.

Features:
 - I2C interface to control panel-specific regulator registers
 - GPIO-based enable/disable support
 - Integration with the Linux regulator framework

This driver is required for proper initialization of Waveshare
MIPI-DSI panels supported by the companion DRM panel driver.

Signed-off-by: Sudarshan Shetty <tessolveupstream@gmail.com>
---
 arch/arm64/configs/defconfig                  |   1 +
 drivers/regulator/Kconfig                     |  11 +
 drivers/regulator/Makefile                    |   1 +
 drivers/regulator/waveshare-panel-regulator.c | 294 ++++++++++++++++++
 4 files changed, 307 insertions(+)
 create mode 100644 drivers/regulator/waveshare-panel-regulator.c

diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index e3a2d37bd104..a1e564024be2 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -1823,3 +1823,4 @@ CONFIG_CORESIGHT_STM=m
 CONFIG_CORESIGHT_CPU_DEBUG=m
 CONFIG_CORESIGHT_CTI=m
 CONFIG_MEMTEST=y
+CONFIG_REGULATOR_WAVESHARE_TOUCHSCREEN=y
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index e6ea2d6f46a4..287ec02220f2 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -1184,6 +1184,17 @@ config REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2
 	  unit. The regulator is used to enable power to the display and to
 	  control backlight PWM.
 
+config REGULATOR_WAVESHARE_TOUCHSCREEN
+	tristate "Waveshare touchscreen panel regulator"
+	depends on BACKLIGHT_CLASS_DEVICE
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Enable support for Waveshare DSI touchscreen panels,
+	  This driver supports regulator on the waveshare
+	  touchscreen unit. The regulator is used to enable power to the
+	  display and to control backlight.
+
 config REGULATOR_RC5T583
 	tristate "RICOH RC5T583 Power regulators"
 	depends on MFD_RC5T583
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index b5befee45379..4c4011be74cd 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -138,6 +138,7 @@ obj-$(CONFIG_REGULATOR_PBIAS) += pbias-regulator.o
 obj-$(CONFIG_REGULATOR_PCAP) += pcap-regulator.o
 obj-$(CONFIG_REGULATOR_RAA215300) += raa215300.o
 obj-$(CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY)  += rpi-panel-attiny-regulator.o
+obj-$(CONFIG_REGULATOR_WAVESHARE_TOUCHSCREEN)  += waveshare-panel-regulator.o
 obj-$(CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2)  += rpi-panel-v2-regulator.o
 obj-$(CONFIG_REGULATOR_RC5T583)  += rc5t583-regulator.o
 obj-$(CONFIG_REGULATOR_RK808)   += rk808-regulator.o
diff --git a/drivers/regulator/waveshare-panel-regulator.c b/drivers/regulator/waveshare-panel-regulator.c
new file mode 100644
index 000000000000..eba068e9592a
--- /dev/null
+++ b/drivers/regulator/waveshare-panel-regulator.c
@@ -0,0 +1,294 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Waveshare International Limited
+ *
+ * Based on rpi-panel-v2-regulator.c by Dave Stevenson <dave.stevenson@raspberrypi.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/of.h>
+
+/* I2C registers of the microcontroller. */
+#define REG_TP 0x94
+#define REG_LCD 0x95
+#define REG_PWM 0x96
+#define REG_SIZE 0x97
+#define REG_ID 0x98
+#define REG_VERSION 0x99
+
+#define NUM_GPIO 16 /* Treat BL_ENABLE, LCD_RESET, TP_RESET as GPIOs */
+
+struct waveshare_panel_lcd {
+	struct mutex dir_lock;
+	struct mutex pwr_lock;
+	struct regmap *regmap;
+	u16 poweron_state;
+	u16 direction_state;
+
+	struct gpio_chip gc;
+	struct gpio_desc *enable;
+};
+
+static const struct regmap_config waveshare_panel_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = REG_PWM,
+};
+
+static int waveshare_panel_gpio_direction_in(struct gpio_chip *gc,
+					     unsigned int offset)
+{
+	struct waveshare_panel_lcd *state = gpiochip_get_data(gc);
+
+	mutex_lock(&state->dir_lock);
+	state->direction_state |= BIT(offset);
+	mutex_unlock(&state->dir_lock);
+
+	return 0;
+}
+
+static int waveshare_panel_gpio_direction_out(struct gpio_chip *gc,
+					      unsigned int offset, int val)
+{
+	struct waveshare_panel_lcd *state = gpiochip_get_data(gc);
+	u16 last_val;
+
+	mutex_lock(&state->dir_lock);
+	state->direction_state &= ~BIT(offset);
+	mutex_unlock(&state->dir_lock);
+
+	mutex_lock(&state->pwr_lock);
+	last_val = state->poweron_state;
+	if (val)
+		last_val |= BIT(offset);
+	else
+		last_val &= ~BIT(offset);
+
+	state->poweron_state = last_val;
+	mutex_unlock(&state->pwr_lock);
+
+	regmap_write(state->regmap, REG_TP, last_val >> 8);
+	regmap_write(state->regmap, REG_LCD, last_val & 0xff);
+
+	return 0;
+}
+
+static int waveshare_panel_gpio_get_direction(struct gpio_chip *gc,
+					      unsigned int offset)
+{
+	struct waveshare_panel_lcd *state = gpiochip_get_data(gc);
+	u16 last_val;
+
+	mutex_lock(&state->dir_lock);
+	last_val = state->direction_state;
+	mutex_unlock(&state->dir_lock);
+
+	if (last_val & BIT(offset))
+		return GPIO_LINE_DIRECTION_IN;
+	else
+		return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int waveshare_panel_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	struct waveshare_panel_lcd *state = gpiochip_get_data(gc);
+	u16 pwr_state;
+
+	mutex_lock(&state->pwr_lock);
+	pwr_state = state->poweron_state & BIT(offset);
+	mutex_unlock(&state->pwr_lock);
+
+	return !!pwr_state;
+}
+
+static int waveshare_panel_gpio_set(struct gpio_chip *gc, unsigned int offset,
+				     int value)
+{
+	struct waveshare_panel_lcd *state = gpiochip_get_data(gc);
+	u16 last_val;
+
+	if (offset >= NUM_GPIO)
+		return 0;
+
+	mutex_lock(&state->pwr_lock);
+
+	last_val = state->poweron_state;
+	if (value)
+		last_val |= BIT(offset);
+	else
+		last_val &= ~BIT(offset);
+
+	state->poweron_state = last_val;
+
+	regmap_write(state->regmap, REG_TP, last_val >> 8);
+	regmap_write(state->regmap, REG_LCD, last_val & 0xff);
+
+	mutex_unlock(&state->pwr_lock);
+
+	return 0;
+}
+
+static int waveshare_panel_update_status(struct backlight_device *bl)
+{
+	struct waveshare_panel_lcd *state = bl_get_data(bl);
+	int brightness = bl->props.brightness;
+
+	if (bl->props.power != FB_BLANK_UNBLANK ||
+	    bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+		brightness = 0;
+
+	if (state->enable)
+		gpiod_set_value_cansleep(state->enable, !!brightness);
+
+	return regmap_write(state->regmap, REG_PWM, brightness);
+}
+
+static const struct backlight_ops waveshare_panel_bl = {
+	.update_status = waveshare_panel_update_status,
+};
+
+static int waveshare_panel_i2c_read(struct i2c_client *client, u8 reg,
+				    unsigned int *buf)
+{
+	int val;
+
+	val = i2c_smbus_read_byte_data(client, reg);
+	if (val < 0)
+		return val;
+
+	*buf = val;
+
+	return 0;
+}
+
+static int waveshare_panel_i2c_probe(struct i2c_client *i2c)
+{
+	struct backlight_properties props = {};
+	struct backlight_device *bl;
+	struct waveshare_panel_lcd *state;
+	struct regmap *regmap;
+	unsigned int data;
+	int ret;
+
+	state = devm_kzalloc(&i2c->dev, sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	mutex_init(&state->dir_lock);
+	mutex_init(&state->pwr_lock);
+
+	i2c_set_clientdata(i2c, state);
+
+	regmap = devm_regmap_init_i2c(i2c, &waveshare_panel_regmap_config);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(&i2c->dev, "Failed to allocate register map: %d\n",
+			ret);
+		goto error;
+	}
+
+	ret = waveshare_panel_i2c_read(i2c, REG_ID, &data);
+	if (ret == 0)
+		dev_info(&i2c->dev, "waveshare panel hw id = 0x%x\n", data);
+
+	ret = waveshare_panel_i2c_read(i2c, REG_SIZE, &data);
+	if (ret == 0)
+		dev_info(&i2c->dev, "waveshare panel size = %d\n", data);
+
+	ret = waveshare_panel_i2c_read(i2c, REG_VERSION, &data);
+	if (ret == 0)
+		dev_info(&i2c->dev, "waveshare panel mcu version = 0x%x\n",
+			 data);
+
+	state->direction_state = 0;
+	state->poweron_state = BIT(9) | BIT(8); // Enable VCC
+	regmap_write(regmap, REG_TP, state->poweron_state >> 8);
+	regmap_write(regmap, REG_LCD, state->poweron_state & 0xff);
+	msleep(20);
+
+	state->regmap = regmap;
+	state->gc.parent = &i2c->dev;
+	state->gc.label = i2c->name;
+	state->gc.owner = THIS_MODULE;
+	state->gc.base = -1;
+	state->gc.ngpio = NUM_GPIO;
+
+	state->gc.get = waveshare_panel_gpio_get;
+	state->gc.set = waveshare_panel_gpio_set;
+	state->gc.direction_input = waveshare_panel_gpio_direction_in;
+	state->gc.direction_output = waveshare_panel_gpio_direction_out;
+	state->gc.get_direction = waveshare_panel_gpio_get_direction;
+	state->gc.can_sleep = true;
+
+	ret = devm_gpiochip_add_data(&i2c->dev, &state->gc, state);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to create gpiochip: %d\n", ret);
+		goto error;
+	}
+
+	state->enable =
+		devm_gpiod_get_optional(&i2c->dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(state->enable))
+		return dev_err_probe(&i2c->dev, PTR_ERR(state->enable),
+				     "Couldn't get enable GPIO\n");
+
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 255;
+	bl = devm_backlight_device_register(&i2c->dev, dev_name(&i2c->dev),
+					    &i2c->dev, state,
+					    &waveshare_panel_bl, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	bl->props.brightness = 255;
+
+	return 0;
+
+error:
+	mutex_destroy(&state->dir_lock);
+	mutex_destroy(&state->pwr_lock);
+	return ret;
+}
+
+static void waveshare_panel_i2c_remove(struct i2c_client *client)
+{
+	struct waveshare_panel_lcd *state = i2c_get_clientdata(client);
+
+	mutex_destroy(&state->dir_lock);
+	mutex_destroy(&state->pwr_lock);
+}
+
+static void waveshare_panel_i2c_shutdown(struct i2c_client *client)
+{
+	struct waveshare_panel_lcd *state = i2c_get_clientdata(client);
+
+	regmap_write(state->regmap, REG_PWM, 0);
+}
+
+static const struct of_device_id waveshare_panel_dt_ids[] = {
+	{ .compatible = "waveshare,touchscreen-panel-regulator" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, waveshare_panel_dt_ids);
+
+static struct i2c_driver waveshare_panel_regulator_driver = {
+	.driver = {
+		.name = "waveshare_touchscreen",
+		.of_match_table = of_match_ptr(waveshare_panel_dt_ids),
+	},
+	.probe = waveshare_panel_i2c_probe,
+	.remove	= waveshare_panel_i2c_remove,
+	.shutdown = waveshare_panel_i2c_shutdown,
+};
+
+module_i2c_driver(waveshare_panel_regulator_driver);
+
+MODULE_AUTHOR("Waveshare Team <support@waveshare.com>");
+MODULE_DESCRIPTION("Regulator device driver for Waveshare touchscreen");
+MODULE_LICENSE("GPL");
-- 
2.34.1