regulator: Add a regulator for the new LCD panels

The newer Raspberry Pi 5" and 7" panels have a slightly different
register map to the original one.
Add a new driver for this regulator.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

drivers/regulator/Kconfig

@@ -1117,6 +1117,16 @@ config REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY
 	  touchscreen unit. The regulator is used to enable power to the
 	  TC358762, display and to control backlight.
 
+config REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2
+	tristate "Raspberry Pi 7-inch touchscreen panel V2 regulator"
+	depends on BACKLIGHT_CLASS_DEVICE
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  This driver supports regulator on the V2 Raspberry Pi
+	  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

drivers/regulator/Makefile

@@ -132,6 +132,7 @@ obj-$(CONFIG_REGULATOR_PCAP) += pcap-regulator.o
 obj-$(CONFIG_REGULATOR_PCF50633) += pcf50633-regulator.o
 obj-$(CONFIG_REGULATOR_RAA215300) += raa215300.o
 obj-$(CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY)  += rpi-panel-attiny-regulator.o
+obj-$(CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2)  += rpi-panel-v2-regulator.o
 obj-$(CONFIG_REGULATOR_RC5T583)  += rc5t583-regulator.o
 obj-$(CONFIG_REGULATOR_RK808)   += rk808-regulator.o
 obj-$(CONFIG_REGULATOR_RN5T618) += rn5t618-regulator.o

drivers/regulator/rpi-panel-v2-regulator.c

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Raspberry Pi Ltd.
+ *
+ * Based on rpi-panel-attiny-regulator.c by Marek Vasut <marex@denx.de>
+ */
+
+#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>
+
+/* I2C registers of the microcontroller. */
+#define REG_ID		0x01
+#define REG_POWERON	0x02
+#define REG_PWM		0x03
+
+// bits for poweron register
+#define LCD_RESET_BIT	BIT(0)
+#define CTP_RESET_BIT	BIT(1)
+
+//bits for the PWM register
+#define PWM_BL_ENABLE	BIT(7)
+#define PWM_VALUE	GENMASK(4, 0)
+
+#define NUM_GPIO	2	/* Treat LCD_RESET and CTP_RESET as GPIOs */
+
+struct rpi_panel_v2_lcd {
+	/* lock to serialise overall accesses to the Atmel */
+	struct mutex	lock;
+	struct regmap	*regmap;
+	u8 poweron_state;
+
+	struct gpio_chip gc;
+};
+
+static const struct regmap_config rpi_panel_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = REG_PWM,
+};
+
+static int rpi_panel_v2_gpio_get_direction(struct gpio_chip *gc, unsigned int off)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void rpi_panel_v2_gpio_set(struct gpio_chip *gc, unsigned int off, int val)
+{
+	struct rpi_panel_v2_lcd *state = gpiochip_get_data(gc);
+	u8 last_val;
+
+	if (off >= NUM_GPIO)
+		return;
+
+	mutex_lock(&state->lock);
+
+	last_val = state->poweron_state;
+	if (val)
+		last_val |= (1 << off);
+	else
+		last_val &= ~(1 << off);
+
+	state->poweron_state = last_val;
+
+	regmap_write(state->regmap, REG_POWERON, last_val);
+
+	mutex_unlock(&state->lock);
+}
+
+static int rpi_panel_v2_update_status(struct backlight_device *bl)
+{
+	struct regmap *regmap = bl_get_data(bl);
+	int brightness = bl->props.brightness;
+
+	if (bl->props.power != FB_BLANK_UNBLANK ||
+	    bl->props.fb_blank != FB_BLANK_UNBLANK)
+		brightness = 0;
+
+	return regmap_write(regmap, REG_PWM, brightness | PWM_BL_ENABLE);
+}
+
+static const struct backlight_ops rpi_panel_v2_bl = {
+	.update_status	= rpi_panel_v2_update_status,
+};
+
+/*
+ * I2C driver interface functions
+ */
+static int rpi_panel_v2_i2c_probe(struct i2c_client *i2c)
+{
+	struct backlight_properties props = { };
+	struct backlight_device *bl;
+	struct rpi_panel_v2_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->lock);
+
+	regmap = devm_regmap_init_i2c(i2c, &rpi_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 = regmap_read(regmap, REG_ID, &data);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Failed to read REG_ID reg: %d\n", ret);
+		goto error;
+	}
+
+	switch (data & 0x0f) {
+	case 0x01: /* 7 inch */
+	case 0x04: /* 7 inch - old */
+	case 0x08: /* 5 inch - old */
+	case 0x09: /* 5 inch */
+		break;
+	default:
+		dev_err(&i2c->dev, "Unknown revision: 0x%02x\n",
+			data & 0x0f);
+		ret = -ENODEV;
+		goto error;
+	}
+
+	regmap_write(regmap, REG_POWERON, 0);
+
+	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.set = rpi_panel_v2_gpio_set;
+	state->gc.get_direction = rpi_panel_v2_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;
+	}
+
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = PWM_VALUE;
+	bl = devm_backlight_device_register(&i2c->dev, dev_name(&i2c->dev),
+					    &i2c->dev, regmap, &rpi_panel_v2_bl,
+					    &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	bl->props.brightness = PWM_VALUE;
+
+	return 0;
+
+error:
+	mutex_destroy(&state->lock);
+	return ret;
+}
+
+static const struct of_device_id rpi_panel_v2_dt_ids[] = {
+	{ .compatible = "raspberrypi,v2-touchscreen-panel-regulator" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, rpi_panel_v2_dt_ids);
+
+static struct i2c_driver rpi_panel_v2_regulator_driver = {
+	.driver = {
+		.name = "rpi_touchscreen_v2",
+		.of_match_table = of_match_ptr(rpi_panel_v2_dt_ids),
+	},
+	.probe = rpi_panel_v2_i2c_probe,
+};
+
+module_i2c_driver(rpi_panel_v2_regulator_driver);
+
+MODULE_AUTHOR("Dave Stevenson <dave.stevenson@raspberrypi.com>");
+MODULE_DESCRIPTION("Regulator device driver for Raspberry Pi 7-inch V2 touchscreen");
+MODULE_LICENSE("GPL");