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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
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tree848558de17fb3008cdf4d861b01ac7781903ce39 /Documentation/driver-api/backlight/lp855x-driver.rst
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Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+====================
+Kernel driver lp855x
+====================
+
+Backlight driver for LP855x ICs
+
+Supported chips:
+
+ Texas Instruments LP8550, LP8551, LP8552, LP8553, LP8555, LP8556 and
+ LP8557
+
+Author: Milo(Woogyom) Kim <milo.kim@ti.com>
+
+Description
+-----------
+
+* 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
+
+ 2) 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.
+
+Examples
+========
+
+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[] = {
+ {EEPROM_A5_ADDR, EEPROM_A5_VAL},
+ };
+
+ 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,
+ };