Kernel driver implementation for LTC3208 Multidisplay LED Driver

Signed-off-by: Jan Carlo Roleda <jancarlo.roleda@analog.com>
---
 MAINTAINERS                 |   1 +
 drivers/leds/Kconfig        |  11 ++
 drivers/leds/Makefile       |   1 +
 drivers/leds/leds-ltc3208.c | 298 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 311 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 3f3331d7272a..48bae02057d5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15131,6 +15131,7 @@ M:	Jan Carlo Roleda <jancarlo.roleda@analog.com>
 L:	linux-leds@vger.kernel.org
 S:	Maintained
 W:	https://ez.analog.com/linux-software-drivers
+F:	drivers/leds/leds-ltc3208.c
 
 LTC4282 HARDWARE MONITOR DRIVER
 M:	Nuno Sa <nuno.sa@analog.com>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 597d7a79c988..867b120ea8ba 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -1029,6 +1029,17 @@ config LEDS_ACER_A500
 	  This option enables support for the Power Button LED of
 	  Acer Iconia Tab A500.
 
+config LEDS_LTC3208
+	tristate "LED Driver for Analog Devices LTC3208"
+	depends on LEDS_CLASS && I2C
+	select REGMAP_I2C
+	help
+	  Say Y to enable the LTC3208 LED driver.
+	  This supports the LED device LTC3208.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called ltc3208.
+
 source "drivers/leds/blink/Kconfig"
 
 comment "Flash and Torch LED drivers"
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 8fdb45d5b439..b08b539112b6 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_LEDS_LP8788)		+= leds-lp8788.o
 obj-$(CONFIG_LEDS_LP8860)		+= leds-lp8860.o
 obj-$(CONFIG_LEDS_LP8864)		+= leds-lp8864.o
 obj-$(CONFIG_LEDS_LT3593)		+= leds-lt3593.o
+obj-$(CONFIG_LEDS_LTC3208)		+= leds-ltc3208.o
 obj-$(CONFIG_LEDS_MAX5970)		+= leds-max5970.o
 obj-$(CONFIG_LEDS_MAX77650)		+= leds-max77650.o
 obj-$(CONFIG_LEDS_MAX77705)		+= leds-max77705.o
diff --git a/drivers/leds/leds-ltc3208.c b/drivers/leds/leds-ltc3208.c
new file mode 100644
index 000000000000..65e65cd73d73
--- /dev/null
+++ b/drivers/leds/leds-ltc3208.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LED driver for Analog Devices LTC3208 Multi-Display Driver
+ *
+ * Copyright 2026 Analog Devices Inc.
+ *
+ * Author: Jan Carlo Roleda <jancarlo.roleda@analog.com>
+ */
+#include <linux/bitfield.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#define LTC3208_SET_HIGH_BYTE_DATA(x)	FIELD_PREP(GENMASK(7, 4), (x))
+
+/* Registers */
+#define LTC3208_REG_A_GRNRED	0x1 /* Green (High half-byte) and Red (Low half-byte) current DAC*/
+#define LTC3208_REG_B_AUXBLU	0x2 /* AUX (High half-byte) and Blue (Low half-byte) current DAC*/
+#define LTC3208_REG_C_MAIN	0x3 /* Main current DAC */
+#define LTC3208_REG_D_SUB	0x4 /* Sub current DAC */
+#define LTC3208_REG_E_AUX	0x5 /* AUX DAC Select */
+#define LTC3208_REG_F_CAM	0x6 /* CAM (High half-byte and Low half-byte) current DAC*/
+#define LTC3208_REG_G_OPT	0x7 /* Device Options */
+
+/* Device Options register */
+#define LTC3208_OPT_CPO_MASK	GENMASK(7, 6)
+#define LTC3208_OPT_DIS_RGBDROP	BIT(3)
+#define LTC3208_OPT_DIS_CAMHILO	BIT(2)
+#define LTC3208_OPT_EN_RGBS	BIT(1)
+
+/* Auxiliary DAC select masks */
+#define LTC3208_AUX1_MASK	GENMASK(1, 0)
+#define LTC3208_AUX2_MASK	GENMASK(3, 2)
+#define LTC3208_AUX3_MASK	GENMASK(5, 4)
+#define LTC3208_AUX4_MASK	GENMASK(7, 6)
+
+#define LTC3208_MAX_BRIGHTNESS_4BIT 0xF
+#define LTC3208_MAX_BRIGHTNESS_8BIT 0xFF
+
+#define LTC3208_NUM_LED_GRPS	8
+#define LTC3208_NUM_AUX_LEDS	4
+
+#define LTC3208_NUM_AUX_OPT	4
+#define LTC3208_MAX_CPO_OPT	3
+
+enum ltc3208_aux_channel {
+	LTC3208_AUX_CHAN_AUX = 0,
+	LTC3208_AUX_CHAN_MAIN,
+	LTC3208_AUX_CHAN_SUB,
+	LTC3208_AUX_CHAN_CAM
+};
+
+enum ltc3208_channel {
+	LTC3208_CHAN_MAIN = 0,
+	LTC3208_CHAN_SUB,
+	LTC3208_CHAN_AUX,
+	LTC3208_CHAN_CAML,
+	LTC3208_CHAN_CAMH,
+	LTC3208_CHAN_RED,
+	LTC3208_CHAN_BLUE,
+	LTC3208_CHAN_GREEN
+};
+
+static const char * const ltc3208_dt_aux_channels[] = {
+	"adi,aux1-channel", "adi,aux2-channel",
+	"adi,aux3-channel", "adi,aux4-channel"
+};
+
+static const char * const ltc3208_aux_opt[] = {
+	"aux", "main", "sub", "cam"
+};
+
+
+struct ltc3208_led {
+	struct led_classdev cdev;
+	struct i2c_client *client;
+	enum ltc3208_channel channel;
+};
+
+struct ltc3208_dev {
+	struct i2c_client *client;
+	struct regmap *map;
+	struct ltc3208_led *leds;
+};
+
+static const struct regmap_config ltc3208_regmap_cfg = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int ltc3208_led_set_brightness(struct led_classdev *led_cdev,
+				      enum led_brightness brightness)
+{
+	struct ltc3208_led *led = container_of(led_cdev,
+					struct ltc3208_led, cdev);
+	struct i2c_client *client = led->client;
+	struct ltc3208_dev *dev = i2c_get_clientdata(client);
+	struct regmap *map = dev->map;
+	u8 current_level = brightness;
+
+	/*
+	 * For registers with 4-bit splits (CAM, AUX/BLUE, GREEN/RED), the other
+	 * half of the byte will be retrieved from the stored DAC value before
+	 * updating the register.
+	 */
+	switch (led->channel) {
+	case LTC3208_CHAN_MAIN:
+		return regmap_write(map, LTC3208_REG_C_MAIN, current_level);
+	case LTC3208_CHAN_SUB:
+		return regmap_write(map, LTC3208_REG_D_SUB, current_level);
+	case LTC3208_CHAN_AUX:
+		/* combine both low and high halves of byte */
+		current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+		current_level |= dev->leds[LTC3208_CHAN_BLUE].cdev.brightness;
+		return regmap_write(map, LTC3208_REG_B_AUXBLU, current_level);
+	case LTC3208_CHAN_BLUE:
+		/* apply high bits stored in other led */
+		current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+			dev->leds[LTC3208_CHAN_AUX].cdev.brightness);
+		return regmap_write(map, LTC3208_REG_B_AUXBLU, current_level);
+	case LTC3208_CHAN_CAMH:
+		current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+		current_level |= dev->leds[LTC3208_CHAN_CAML].cdev.brightness;
+		return regmap_write(map, LTC3208_REG_F_CAM, current_level);
+	case LTC3208_CHAN_CAML:
+		current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+			dev->leds[LTC3208_CHAN_CAMH].cdev.brightness);
+		return regmap_write(map, LTC3208_REG_F_CAM, current_level);
+	case LTC3208_CHAN_GREEN:
+		current_level = LTC3208_SET_HIGH_BYTE_DATA(current_level);
+		current_level |= dev->leds[LTC3208_CHAN_RED].cdev.brightness;
+		return regmap_write(map, LTC3208_REG_A_GRNRED, current_level);
+	case LTC3208_CHAN_RED:
+		current_level |= LTC3208_SET_HIGH_BYTE_DATA(
+			dev->leds[LTC3208_CHAN_GREEN].cdev.brightness);
+		return regmap_write(map, LTC3208_REG_A_GRNRED, current_level);
+	default:
+		dev_err(&client->dev, "Invalid LED Channel\n");
+		return -EINVAL;
+	}
+}
+
+static int ltc3208_update_options(struct ltc3208_dev *dev,
+				  bool is_sub, bool is_cam_hi, bool is_rgb_drop)
+{
+	struct regmap *map = dev->map;
+	u8 val =	FIELD_PREP(LTC3208_OPT_EN_RGBS, is_sub) |
+			FIELD_PREP(LTC3208_OPT_DIS_CAMHILO, is_cam_hi) |
+			FIELD_PREP(LTC3208_OPT_DIS_RGBDROP, is_rgb_drop);
+
+	return regmap_write(map, LTC3208_REG_G_OPT, val);
+}
+
+static int ltc3208_update_aux_dac(struct ltc3208_dev *dev,
+	enum ltc3208_aux_channel aux_1, enum ltc3208_aux_channel aux_2,
+	enum ltc3208_aux_channel aux_3, enum ltc3208_aux_channel aux_4)
+{
+	struct regmap *map = dev->map;
+	u8 val =	FIELD_PREP(LTC3208_AUX1_MASK, aux_1) |
+			FIELD_PREP(LTC3208_AUX2_MASK, aux_2) |
+			FIELD_PREP(LTC3208_AUX3_MASK, aux_3) |
+			FIELD_PREP(LTC3208_AUX4_MASK, aux_4);
+
+	return regmap_write(map, LTC3208_REG_E_AUX, val);
+}
+
+static int ltc3208_probe(struct i2c_client *client)
+{
+	enum ltc3208_aux_channel aux_channels[LTC3208_NUM_AUX_LEDS];
+	struct ltc3208_dev *data;
+	struct ltc3208_led *leds;
+	struct regmap *map;
+	int ret, i;
+	u32 val;
+	bool dropdis_rgb_aux4;
+	bool dis_camhl;
+	bool en_rgbs;
+
+	map = devm_regmap_init_i2c(client, &ltc3208_regmap_cfg);
+	if (IS_ERR(map))
+		return dev_err_probe(&client->dev, PTR_ERR(map),
+				     "Failed to initialize regmap\n");
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	leds = devm_kcalloc(&client->dev, LTC3208_NUM_LED_GRPS,
+			    sizeof(struct ltc3208_led), GFP_KERNEL);
+	if (!leds)
+		return -ENOMEM;
+
+	data->client = client;
+	data->map = map;
+
+	/* initialize options from devicetree */
+	dis_camhl = device_property_read_bool(&client->dev,
+					      "adi,disable-camhl-pin");
+	en_rgbs = device_property_read_bool(&client->dev,
+					    "adi,cfg-enrgbs-pin");
+	dropdis_rgb_aux4 = device_property_read_bool(&client->dev,
+						     "adi,disable-rgb-aux4-dropout");
+
+	ret = ltc3208_update_options(data, en_rgbs, dis_camhl,
+				     dropdis_rgb_aux4);
+	if (ret)
+		return dev_err_probe(&client->dev, ret,
+				     "error writing to options register\n");
+
+	/* initialize aux channel configurations from devicetree */
+	for (i = 0; i < LTC3208_NUM_AUX_LEDS; i++) {
+		ret = device_property_match_property_string(&client->dev,
+							    ltc3208_dt_aux_channels[i],
+							    ltc3208_aux_opt,
+							    LTC3208_NUM_AUX_OPT);
+		/* use default value if absent in devicetree */
+		if (ret == -EINVAL)
+			aux_channels[i] = LTC3208_AUX_CHAN_AUX;
+		else if (ret >= 0)
+			aux_channels[i] = ret;
+		else
+			return dev_err_probe(&client->dev, ret,
+					     "Failed getting aux-channel.\n");
+	}
+
+	ret = ltc3208_update_aux_dac(data, aux_channels[0], aux_channels[1],
+				     aux_channels[2], aux_channels[3]);
+	if (ret)
+		return dev_err_probe(&client->dev, ret,
+				     "error writing to aux %u channel register.\n", i);
+
+	i2c_set_clientdata(client, data);
+
+	device_for_each_child_node_scoped(&client->dev, child) {
+		struct ltc3208_led *led;
+		struct led_init_data init_data = {};
+
+		ret = fwnode_property_read_u32(child, "reg", &val);
+		if (ret || val >= LTC3208_NUM_LED_GRPS)
+			return dev_err_probe(&client->dev, -EINVAL,
+					     "Invalid reg property for LED\n");
+
+		led = &leds[val];
+		led->client = client;
+		led->channel = val;
+		led->cdev.brightness_set_blocking = ltc3208_led_set_brightness;
+		led->cdev.max_brightness = LTC3208_MAX_BRIGHTNESS_4BIT;
+		if (val == LTC3208_CHAN_MAIN || val == LTC3208_CHAN_SUB)
+			led->cdev.max_brightness = LTC3208_MAX_BRIGHTNESS_8BIT;
+
+		init_data.fwnode = child;
+
+		ret = devm_led_classdev_register_ext(&client->dev, &led->cdev,
+			&init_data);
+		if (ret)
+			return dev_err_probe(&client->dev, ret,
+					     "Failed to register LED %u\n", val);
+	}
+
+	data->leds = leds;
+
+	return 0;
+}
+
+static const struct of_device_id ltc3208_match_table[] = {
+	{.compatible = "adi,ltc3208"},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ltc3208_match_table);
+
+static const struct i2c_device_id ltc3208_idtable[] = {
+	{ "ltc3208" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc3208_idtable);
+
+static struct i2c_driver ltc3208_driver = {
+	.driver = {
+		.name = "ltc3208",
+		.of_match_table = ltc3208_match_table,
+	},
+	.id_table = ltc3208_idtable,
+	.probe = ltc3208_probe,
+};
+module_i2c_driver(ltc3208_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jan Carlo Roleda <jancarlo.roleda@analog.com>");
+MODULE_DESCRIPTION("LTC3208 LED Driver");

-- 
2.43.0