video: backlight: Add support for Richtek RT8555 Backlight

The Richtek RT8555 is a 6 channel LED driver that supports
up to 35mA/LED. This is a backlight driver that drives ILED1.

Signed-off-by: Michael Abood <[email protected]>

Author: person4268

drivers/video/backlight/Kconfig

@@ -297,6 +297,15 @@ config BACKLIGHT_RT4831
 	  It's commonly used to drive the display WLED. There're four channels
 	  inisde, and each channel can provide up to 30mA current.
 
+config BACKLIGHT_RT8555
+	tristate "Richtek RT8555 Backlight Driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  This enables support for Richtek RT8555 Backlight driver.
+	  It's commonly used to drive the display WLED. There are six channels
+	  inisde, and each channel can provide up to 35mA current.
+
 config BACKLIGHT_SAHARA
 	tristate "Tabletkiosk Sahara Touch-iT Backlight Driver"
 	depends on X86

drivers/video/backlight/Makefile

@@ -50,6 +50,7 @@ obj-$(CONFIG_BACKLIGHT_PCF50633)	+= pcf50633-backlight.o
 obj-$(CONFIG_BACKLIGHT_PWM)		+= pwm_bl.o
 obj-$(CONFIG_BACKLIGHT_QCOM_WLED)	+= qcom-wled.o
 obj-$(CONFIG_BACKLIGHT_RT4831)		+= rt4831-backlight.o
+obj-$(CONFIG_BACKLIGHT_RT8555)		+= rt8555-backlight.o
 obj-$(CONFIG_BACKLIGHT_SAHARA)		+= kb3886_bl.o
 obj-$(CONFIG_BACKLIGHT_SKY81452)	+= sky81452-backlight.o
 obj-$(CONFIG_BACKLIGHT_TOSA)		+= tosa_bl.o

drivers/video/backlight/rt8555-backlight.c

@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <dt-bindings/leds/rt4831-backlight.h>
+#include <linux/backlight.h>
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/gpio/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define RT8555_MAX_BRIGHTNESS 1023
+
+#define RT8555_REG_CFG1 0x01
+#define RT8555_REG_ILED1_LSB 0x04
+#define RT8555_REG_ILED1_MSB 0x05
+
+#define RT8555_EN10BIT_MASK BIT(7)
+#define RT8555_LSB_MASK GENMASK(7, 0)
+
+struct rt8555_priv {
+	struct device *dev;
+	struct regmap *regmap;
+	struct backlight_device *bl;
+	struct gpio_desc *enable;
+};
+
+static int rt8555_bl_update_status(struct backlight_device *bl_dev)
+{
+	struct rt8555_priv *priv = bl_get_data(bl_dev);
+	unsigned int brightness = min(backlight_get_brightness(bl_dev), RT8555_MAX_BRIGHTNESS);
+	int ret;
+
+	/* Enable the IC before setting the brightness */
+	if (brightness)
+			if (!IS_ERR(priv->enable))
+				gpiod_set_value(priv->enable, 1);
+
+
+	ret = regmap_write(priv->regmap, RT8555_REG_ILED1_LSB, (brightness & RT8555_LSB_MASK));
+	if (ret)
+		return ret;
+
+	ret = regmap_write(priv->regmap, RT8555_REG_ILED1_MSB, (brightness >> 8));
+	if (ret)
+		return ret;
+
+	/* Disable the IC after setting it to 0 */
+	if (brightness == 0)
+			if (!IS_ERR(priv->enable))
+				gpiod_set_value(priv->enable, 0);
+
+	return 0;
+}
+
+static int rt8555_bl_get_brightness(struct backlight_device *bl_dev)
+{
+	struct rt8555_priv *priv = bl_get_data(bl_dev);
+	int ret, msb, lsb;
+
+	/* If the RT8555 is disabled, there's no reason to turn it on just to read
+	 * it back */
+	if (!IS_ERR(priv->enable))
+		if (gpiod_get_value(priv->enable) == 0)
+			return 0;
+
+	ret = regmap_read(priv->regmap, RT8555_REG_ILED1_MSB, &msb);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(priv->regmap, RT8555_REG_ILED1_LSB, &lsb);
+	if (ret)
+		return ret;
+
+	ret = (lsb >> 8) & msb;
+	return ret;
+}
+
+static const struct backlight_ops rt8555_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = rt8555_bl_update_status,
+	.get_brightness = rt8555_bl_get_brightness,
+};
+
+static const struct regmap_config rt8555_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+};
+
+static int rt8555_bl_probe(struct i2c_client *client)
+{
+	struct rt8555_priv *priv;
+	struct backlight_properties bl_props = { .type = BACKLIGHT_RAW,
+						 .scale = BACKLIGHT_SCALE_LINEAR };
+	int ret;
+	u32 brightness;
+
+	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = &client->dev;
+
+	priv->enable = devm_gpiod_get_optional(&client->dev, NULL, GPIOD_OUT_HIGH);
+	if (!IS_ERR(priv->enable))
+		gpiod_set_value(priv->enable, 1);
+
+	ret = device_property_read_u32(&client->dev, "max-brightness", &brightness);
+	if (ret)
+		brightness = RT8555_MAX_BRIGHTNESS;
+
+	bl_props.max_brightness = min_t(u32, brightness, RT8555_MAX_BRIGHTNESS);
+
+	ret = device_property_read_u32(&client->dev, "default-brightness", &brightness);
+	if (ret)
+		brightness = bl_props.max_brightness;
+
+	bl_props.brightness = min_t(u32, brightness, bl_props.max_brightness);
+
+	priv->bl = devm_backlight_device_register(&client->dev, client->name, &client->dev, priv,
+						  &rt8555_bl_ops, &bl_props);
+	if (IS_ERR(priv->bl)) {
+		dev_err(&client->dev, "Failed to register backlight\n");
+		return PTR_ERR(priv->bl);
+	}
+
+	/* Set 10 bit mode */
+	ret = regmap_update_bits(priv->regmap, RT8555_REG_CFG1, RT8555_EN10BIT_MASK, BIT(7));
+	if (ret)
+		return ret;
+
+	backlight_update_status(priv->bl);
+	i2c_set_clientdata(client, priv);
+
+	return 0;
+}
+
+static void rt8555_bl_remove(struct i2c_client *client)
+{
+	struct rt8555_priv *priv = i2c_get_clientdata(client);
+	struct backlight_device *bl_dev = priv->bl;
+
+	bl_dev->props.brightness = 0;
+	backlight_update_status(priv->bl);
+
+	if (!IS_ERR(priv->enable))
+		gpiod_set_value(priv->enable, 0);
+}
+
+static const struct of_device_id __maybe_unused rt8555_bl_of_match[] = {
+	{ .compatible = "richtek,rt8555-backlight", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, rt8555_bl_of_match);
+
+static struct i2c_driver rt8555_bl_driver = {
+	.driver = {
+		.name = "rt8555-backlight",
+		.of_match_table = rt8555_bl_of_match
+	},
+	.probe_new = rt8555_bl_probe,
+	.shutdown = rt8555_bl_remove
+};
+module_i2c_driver(rt8555_bl_driver);
+MODULE_AUTHOR("Michael Abood <[email protected]>");
+MODULE_LICENSE("GPL v2");