@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2025-2026 Roman Vivchar <rva333@protonmail.com>
+ *
+ * Backlight driver for the Kinetic KTD3137
+ */
+
+#include <linux/backlight.h>
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+
+#define KTD3137_REG_DEV_ID 0x00
+#define KTD3137_REG_SW_RESET 0x01
+#define KTD3137_REG_MODE 0x02
+#define KTD3137_REG_CONTROL 0x03
+#define KTD3137_REG_RATIO_LSB 0x04
+#define KTD3137_REG_RATIO_MSB 0x05
+#define KTD3137_REG_PWM 0x06
+#define KTD3137_REG_RAMP_ON 0x07
+#define KTD3137_REG_TRANS_RAMP 0x08
+#define KTD3137_REG_FLASH_SETTING 0x09
+#define KTD3137_REG_STATUS 0x0a
+#define KTD3137_REG_MAX 0x0a
+
+/* KTD3137_REG_DEV_ID */
+#define KTD3137_DEV_ID_A 0x12
+#define KTD3137_DEV_ID_B 0x18
+
+/* KTD3137_REG_MODE */
+#define KTD3137_MODE_BL_EN BIT(0)
+#define KTD3137_MODE_CURRENT_MASK GENMASK(7, 3)
+
+/* KTD3137_REG_CONTROL */
+#define KTD3137_CONTROL_LINEAR (BIT(1) | BIT(2))
+#define KTD3137_CONTROL_IND_2P6A BIT(3)
+#define KTD3137_CONTROL_OVP_32V BIT(5)
+#define KTD3137_CONTROL_FREQ_1000KHZ BIT(6)
+#define KTD3137_CONTROL_DEFAULT (KTD3137_CONTROL_IND_2P6A | \
+ KTD3137_CONTROL_OVP_32V | \
+ KTD3137_CONTROL_FREQ_1000KHZ)
+
+/* KTD3137_REG_RATIO_LSB */
+#define KTD3137_RATIO_LSB_MASK GENMASK(2, 0)
+
+/* KTD3137_REG_PWM */
+#define KTD3137_PWM_CH1_EN BIT(0)
+#define KTD3137_PWM_CH2_EN BIT(1)
+#define KTD3137_PWM_FILTER_6LSB (BIT(3) | BIT(4))
+#define KTD3137_PWM_DISABLE BIT(7)
+#define KTD3137_PWM_DEFAULT (KTD3137_PWM_CH1_EN | \
+ KTD3137_PWM_CH2_EN | \
+ KTD3137_PWM_FILTER_6LSB | \
+ KTD3137_PWM_DISABLE)
+
+/* KTD3137_REG_RAMP_ON */
+#define KTD3137_RAMP_ON_MASK GENMASK(7, 4)
+#define KTD3137_RAMP_OFF_MASK GENMASK(3, 0)
+/* Ramp ON: 2ms, OFF: 8ms */
+#define KTD3137_RAMP_DEFAULT (FIELD_PREP(KTD3137_RAMP_ON_MASK, 4) | \
+ FIELD_PREP(KTD3137_RAMP_OFF_MASK, 4))
+
+#define KTD3137_DEFAULT_BRIGHTNESS 2047
+#define KTD3137_MAX_BRIGHTNESS 2047
+
+#define KTD3137_I_MIN_UA 5000
+#define KTD3137_I_MAX_UA 29800
+#define KTD3137_I_STEP_UA 800
+#define KTD3137_I_DEFAULT_UA 20200
+
+struct ktd3137 {
+ struct device *dev;
+ struct regmap *regmap;
+ struct gpio_desc *enable_gpio;
+ u32 led_current;
+};
+
+static const struct regmap_config ktd3137_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = KTD3137_REG_MAX,
+};
+
+static int ktd3137_init(struct ktd3137 *ktd)
+{
+ u32 val = KTD3137_CONTROL_DEFAULT | KTD3137_CONTROL_LINEAR;
+ int ret;
+
+ ret = regmap_write(ktd->regmap, KTD3137_REG_CONTROL, val);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(ktd->regmap, KTD3137_REG_PWM, KTD3137_PWM_DEFAULT);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(ktd->regmap, KTD3137_REG_RAMP_ON, KTD3137_RAMP_DEFAULT);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(ktd->regmap, KTD3137_REG_TRANS_RAMP, 0x00);
+ if (ret)
+ return ret;
+
+ return regmap_update_bits(ktd->regmap, KTD3137_REG_MODE,
+ KTD3137_MODE_CURRENT_MASK, ktd->led_current);
+}
+
+static int ktd3137_backlight_update_status(struct backlight_device *backlight_dev)
+{
+ struct ktd3137 *ktd = bl_get_data(backlight_dev);
+ unsigned int brightness = backlight_get_brightness(backlight_dev);
+ int ret;
+
+ if (brightness > 0) {
+ ret = regmap_write(ktd->regmap, KTD3137_REG_RATIO_LSB,
+ brightness & KTD3137_RATIO_LSB_MASK);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(ktd->regmap, KTD3137_REG_RATIO_MSB,
+ brightness >> 3);
+ if (ret)
+ return ret;
+ }
+
+ return regmap_update_bits(ktd->regmap, KTD3137_REG_MODE,
+ KTD3137_MODE_BL_EN,
+ brightness ? KTD3137_MODE_BL_EN : 0);
+}
+
+static const struct backlight_ops ktd3137_backlight_ops = {
+ .options = BL_CORE_SUSPENDRESUME,
+ .update_status = ktd3137_backlight_update_status,
+};
+
+static int ktd3137_parse_dt(struct ktd3137 *ktd)
+{
+ u32 max_ua = KTD3137_I_DEFAULT_UA;
+ u32 val;
+
+ device_property_read_u32(ktd->dev, "led-max-microamp", &max_ua);
+
+ if (max_ua < KTD3137_I_MIN_UA || max_ua > KTD3137_I_MAX_UA)
+ return dev_err_probe(ktd->dev, -EINVAL,
+ "led-max-microamp (%u) out of range\n", max_ua);
+
+ val = (max_ua - KTD3137_I_MIN_UA) / KTD3137_I_STEP_UA;
+ ktd->led_current = FIELD_PREP(KTD3137_MODE_CURRENT_MASK, val);
+
+ return 0;
+}
+
+static int ktd3137_probe(struct i2c_client *client)
+{
+ struct backlight_device *backlight_dev;
+ struct backlight_properties props = { };
+ struct ktd3137 *ktd;
+ u32 val;
+ int ret;
+
+ ktd = devm_kzalloc(&client->dev, sizeof(*ktd), GFP_KERNEL);
+ if (!ktd)
+ return -ENOMEM;
+
+ ktd->dev = &client->dev;
+
+ ret = devm_regulator_get_enable(ktd->dev, "vin");
+ if (ret)
+ return dev_err_probe(ktd->dev, ret, "failed to power up\n");
+
+ ktd->enable_gpio = devm_gpiod_get_optional(ktd->dev, "enable",
+ GPIOD_OUT_HIGH);
+ if (IS_ERR(ktd->enable_gpio))
+ return dev_err_probe(ktd->dev, PTR_ERR(ktd->enable_gpio),
+ "failed to get enable gpio\n");
+
+ /* HWEN should stay HIGH for at least 150us before I2C can be used */
+ fsleep(150);
+
+ ktd->regmap = devm_regmap_init_i2c(client, &ktd3137_regmap_config);
+ if (IS_ERR(ktd->regmap))
+ return dev_err_probe(ktd->dev, PTR_ERR(ktd->regmap),
+ "failed to init regmap\n");
+
+ ret = regmap_read(ktd->regmap, KTD3137_REG_DEV_ID, &val);
+ if (ret)
+ return dev_err_probe(ktd->dev, ret, "failed to read chip id\n");
+
+ if (val != KTD3137_DEV_ID_A && val != KTD3137_DEV_ID_B)
+ return dev_err_probe(ktd->dev, -ENODEV,
+ "unsupported chip id: 0x%02x\n", val);
+
+ ret = ktd3137_parse_dt(ktd);
+ if (ret)
+ return ret;
+
+ ret = ktd3137_init(ktd);
+ if (ret)
+ return dev_err_probe(ktd->dev, ret, "failed to init chip\n");
+
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = KTD3137_MAX_BRIGHTNESS;
+ props.brightness = KTD3137_DEFAULT_BRIGHTNESS;
+ props.scale = BACKLIGHT_SCALE_LINEAR;
+ device_property_read_u32(ktd->dev, "default-brightness", &props.brightness);
+
+ backlight_dev = devm_backlight_device_register(ktd->dev,
+ "ktd3137-backlight",
+ ktd->dev, ktd,
+ &ktd3137_backlight_ops,
+ &props);
+ if (IS_ERR(backlight_dev))
+ return dev_err_probe(ktd->dev, PTR_ERR(backlight_dev),
+ "failed to register backlight device\n");
+
+ i2c_set_clientdata(client, backlight_dev);
+ return backlight_update_status(backlight_dev);
+}
+
+static void ktd3137_remove(struct i2c_client *client)
+{
+ struct backlight_device *backlight_dev = i2c_get_clientdata(client);
+ struct ktd3137 *ktd = bl_get_data(backlight_dev);
+
+ backlight_dev->props.brightness = 0;
+ backlight_update_status(backlight_dev);
+
+ gpiod_set_value_cansleep(ktd->enable_gpio, 0);
+}
+
+static const struct i2c_device_id ktd3137_ids[] = {
+ { "ktd3137" },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, ktd3137_ids);
+
+static const struct of_device_id ktd3137_match_table[] = {
+ { .compatible = "kinetic,ktd3137" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ktd3137_match_table);
+
+static struct i2c_driver ktd3137_driver = {
+ .driver = {
+ .name = "ktd3137",
+ .of_match_table = ktd3137_match_table,
+ },
+ .probe = ktd3137_probe,
+ .remove = ktd3137_remove,
+ .id_table = ktd3137_ids,
+};
+module_i2c_driver(ktd3137_driver);
+
+MODULE_DESCRIPTION("Kinetic KTD3137 Backlight Driver");
+MODULE_LICENSE("GPL");