# \[PATCH 2/2\] backlight: add ktd3137 support - From: Roman Vivchar via B4 Relay \ - Date: 2026-11-02 19:58:52 - List: linux-fbdev - Page: https://ratatoskr.run/linux-fbdev/2026/11/17847319 - Thread: https://ratatoskr.run/dri-devel/2026/11/17847320/t.md ```text From: Roman Vivchar Add support for the KTD3137 display backlight IC. It's used in various Xiaomi phones, such as Xiaomi Redmi Note 9. Signed-off-by: Roman Vivchar --- MAINTAINERS | 1 + drivers/video/backlight/Kconfig | 11 ++ drivers/video/backlight/Makefile | 1 + drivers/video/backlight/ktd3137.c | 262 ++++++++++++++++++++++++++++++++++++++ 4 files changed, 275 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index 24dd5b43f167..23114fd09445 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -14622,6 +14622,7 @@ KTD3137 BACKLIGHT DRIVER M: Roman Vivchar S: Maintained F: Documentation/devicetree/bindings/leds/backlight/kinetic,ktd3137.yaml +F: drivers/video/backlight/ktd3137.c KTEST M: Steven Rostedt diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig index 7c66b8840d88..0196b8597367 100644 --- a/drivers/video/backlight/Kconfig +++ b/drivers/video/backlight/Kconfig @@ -199,6 +199,17 @@ config BACKLIGHT_KTD2801 Say Y to enable the backlight driver for the Kinetic KTD2801 1-wire GPIO-controlled backlight found in Samsung Galaxy Core Prime VE LTE. +config BACKLIGHT_KTD3137 + tristate "Backlight Driver for Kinetic KTD3137" + depends on I2C + select REGMAP_I2C + help + Say Y to enable the backlight driver for the Kinetic KTD3137 + found in various Xiaomi smartphones. + + To compile this driver as a module, choose M here: the module + will be called ktd3137. + config BACKLIGHT_KTZ8866 tristate "Backlight Driver for Kinetic KTZ8866" depends on I2C diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile index 34469711c6cd..b2d3b69e9e32 100644 --- a/drivers/video/backlight/Makefile +++ b/drivers/video/backlight/Makefile @@ -38,6 +38,7 @@ obj-$(CONFIG_BACKLIGHT_HP700) += jornada720_bl.o obj-$(CONFIG_BACKLIGHT_IPAQ_MICRO) += ipaq_micro_bl.o obj-$(CONFIG_BACKLIGHT_KTD253) += ktd253-backlight.o obj-$(CONFIG_BACKLIGHT_KTD2801) += ktd2801-backlight.o +obj-$(CONFIG_BACKLIGHT_KTD3137) += ktd3137.o obj-$(CONFIG_BACKLIGHT_KTZ8866) += ktz8866.o obj-$(CONFIG_BACKLIGHT_LM3509) += lm3509_bl.o obj-$(CONFIG_BACKLIGHT_LM3533) += lm3533_bl.o diff --git a/drivers/video/backlight/ktd3137.c b/drivers/video/backlight/ktd3137.c new file mode 100644 index 000000000000..a3ff334b8d46 --- /dev/null +++ b/drivers/video/backlight/ktd3137.c @@ -0,0 +1,262 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (c) 2025-2026 Roman Vivchar + * + * Backlight driver for the Kinetic KTD3137 + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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"); -- 2.56.0 ```