Kernel driver lp855x

Backlight driver for LP855x ICs

Supported chips:

Texas Instruments LP8550, LP8551, LP8552, LP8553, LP8555, LP8556 and LP8557

Author: Milo(Woogyom) Kim <>


  • Brightness control

    Brightness can be controlled by the pwm input or the i2c command. The lp855x driver supports both cases.

  • Device attributes

    1. bl_ctl_mode

    Backlight control mode.

    Value: pwm based or register based

    1. chip_id

    The lp855x chip id.

    Value: lp8550/lp8551/lp8552/lp8553/lp8555/lp8556/lp8557

Platform data for lp855x

For supporting platform specific data, the lp855x platform data can be used.

  • name:

    Backlight driver name. If it is not defined, default name is set.

  • device_control:

    Value of DEVICE CONTROL register.

  • initial_brightness:

    Initial value of backlight brightness.

  • period_ns:

    Platform specific PWM period value. unit is nano. Only valid when brightness is pwm input mode.

  • size_program:

    Total size of lp855x_rom_data.

  • rom_data:

    List of new eeprom/eprom registers.


  1. lp8552 platform data: i2c register mode with new eeprom data:

    #define EEPROM_A5_ADDR      0xA5
    #define EEPROM_A5_VAL       0x4f    /* EN_VSYNC=0 */
    static struct lp855x_rom_data lp8552_eeprom_arr[] = {
    static struct lp855x_platform_data lp8552_pdata = {
        .name = "lcd-bl",
        .device_control = I2C_CONFIG(LP8552),
        .initial_brightness = INITIAL_BRT,
        .size_program = ARRAY_SIZE(lp8552_eeprom_arr),
        .rom_data = lp8552_eeprom_arr,
  2. lp8556 platform data: pwm input mode with default rom data:

    static struct lp855x_platform_data lp8556_pdata = {
        .device_control = PWM_CONFIG(LP8556),
        .initial_brightness = INITIAL_BRT,
        .period_ns = 1000000,