[PATCH v1 5/5] video: backlight: add Samsung CMC623 backlight PWM driver

[Ion Agorria]

Add support for PWM backlight found in Samsung CMC623 image converter.

Signed-off-by: Ion Agorria <ion at agorria.com>
---
 drivers/video/Kconfig            |   7 ++
 drivers/video/Makefile           |   1 +
 drivers/video/cmc623_backlight.c | 124 +++++++++++++++++++++++++++++++
 3 files changed, 132 insertions(+)
 create mode 100644 drivers/video/cmc623_backlight.c

diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index a02501583eb..b5777da5218 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -838,6 +838,13 @@ config BACKLIGHT_LP855x
 	  supported for now, PWM mode can be added if there will be any need in
 	  it. Supported backlight level range is from 0 to 255 with step of 1.
 
+config BACKLIGHT_SAMSUNG_CMC623
+	bool "Backlight Driver for Samsung CMC623"
+	depends on VIDEO_BRIDGE_SAMSUNG_CMC623
+	help
+	  Say Y to enable the backlight driver for Samsung CMC623 image converter
+	  chip's PWM output to control backlight brightness.
+
 source "drivers/video/ti/Kconfig"
 
 source "drivers/video/exynos/Kconfig"
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 040333fb3a6..96c7ce7bb09 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_BACKLIGHT_AAT2870) += aat2870_backlight.o
 obj-$(CONFIG_BACKLIGHT_LM3532) += lm3532_backlight.o
 obj-$(CONFIG_BACKLIGHT_LM3533) += lm3533_backlight.o
 obj-$(CONFIG_BACKLIGHT_LP855x) += lp855x_backlight.o
+obj-$(CONFIG_BACKLIGHT_SAMSUNG_CMC623) += cmc623_backlight.o
 obj-${CONFIG_EXYNOS_FB} += exynos/
 obj-${CONFIG_VIDEO_ROCKCHIP} += rockchip/
 obj-${CONFIG_VIDEO_STM32} += stm32/
diff --git a/drivers/video/cmc623_backlight.c b/drivers/video/cmc623_backlight.c
new file mode 100644
index 00000000000..84b01724a07
--- /dev/null
+++ b/drivers/video/cmc623_backlight.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2025 Ion Agorria <ion at agorria.com>
+ */
+
+#define LOG_CATEGORY UCLASS_PANEL_BACKLIGHT
+
+#include <backlight.h>
+#include <dm.h>
+#include <i2c.h>
+#include <log.h>
+#include <linux/err.h>
+#include <asm/gpio.h>
+#include <power/regulator.h>
+
+#define CMC623_I2C_REG_SELBANK		0x00
+#define CMC623_I2C_REG_PWMCTRL		0xb4
+#define CMC623_I2C_REG_REGMASK		0x28
+
+#define CMC623_BL_MIN_BRIGHTNESS	0
+#define CMC623_BL_DEF_BRIGHTNESS	50
+#define CMC623_BL_MAX_BRIGHTNESS	100
+
+struct cmc623_backlight_priv {
+	struct gpio_desc enable_gpio;
+};
+
+static int cmc623_backlight_enable(struct udevice *dev)
+{
+	struct cmc623_backlight_priv *priv = dev_get_priv(dev);
+
+	if (dm_gpio_is_valid(&priv->enable_gpio))
+		dm_gpio_set_value(&priv->enable_gpio, 1);
+
+	return 0;
+}
+
+static int cmc623_i2c_write(struct udevice *dev, u8 reg, u16 value)
+{
+	u8 data[2];
+
+	data[0] = (value >> 8) & 0xff;
+	data[1] = value & 0xff;
+
+	return dm_i2c_write(dev->parent, reg, data, 2);
+}
+
+static int cmc623_backlight_set_brightness(struct udevice *dev, int percent)
+{
+	int ret;
+	u16 brightness;
+
+	if (percent == BACKLIGHT_DEFAULT)
+		percent = CMC623_BL_DEF_BRIGHTNESS;
+
+	if (percent < CMC623_BL_MIN_BRIGHTNESS)
+		percent = CMC623_BL_MIN_BRIGHTNESS;
+
+	if (percent > CMC623_BL_MAX_BRIGHTNESS)
+		percent = CMC623_BL_MAX_BRIGHTNESS;
+
+	brightness = 0x4000 | (percent << 4);
+
+	ret = cmc623_i2c_write(dev, CMC623_I2C_REG_SELBANK, 0x0000);
+	if (ret) {
+		log_debug("%s: error at CMC623_I2C_REG_SELBANK (%d)\n",
+			  __func__, ret);
+		return ret;
+	}
+
+	ret = cmc623_i2c_write(dev, CMC623_I2C_REG_PWMCTRL, brightness);
+	if (ret) {
+		log_debug("%s: error at CMC623_I2C_REG_PWMCTRL (%d)\n",
+			  __func__, ret);
+		return ret;
+	}
+
+	ret = cmc623_i2c_write(dev, CMC623_I2C_REG_REGMASK, 0x0000);
+	if (ret) {
+		log_debug("%s: error at CMC623_I2C_REG_REGMASK (%d)\n",
+			  __func__, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int cmc623_backlight_of_to_plat(struct udevice *dev)
+{
+	struct cmc623_backlight_priv *priv = dev_get_priv(dev);
+
+	gpio_request_by_name(dev, "enable-gpios", 0,
+			     &priv->enable_gpio, GPIOD_IS_OUT);
+
+	return 0;
+}
+
+static int cmc623_backlight_probe(struct udevice *dev)
+{
+	if (device_get_uclass_id(dev->parent) != UCLASS_VIDEO_BRIDGE)
+		return -EPROTONOSUPPORT;
+
+	return 0;
+}
+
+static const struct backlight_ops cmc623_backlight_ops = {
+	.enable = cmc623_backlight_enable,
+	.set_brightness = cmc623_backlight_set_brightness,
+};
+
+static const struct udevice_id cmc623_backlight_ids[] = {
+	{ .compatible = "samsung,cmc623-backlight" },
+	{ }
+};
+
+U_BOOT_DRIVER(cmc623_backlight) = {
+	.name		= "cmc623_backlight",
+	.id		= UCLASS_PANEL_BACKLIGHT,
+	.of_match	= cmc623_backlight_ids,
+	.of_to_plat	= cmc623_backlight_of_to_plat,
+	.probe		= cmc623_backlight_probe,
+	.ops		= &cmc623_backlight_ops,
+	.priv_auto	= sizeof(struct cmc623_backlight_priv),
+};
-- 
2.50.0