Commit 607fbac0 authored by Hans de Goede's avatar Hans de Goede
Browse files

platform/x86: x86-android-tablets: Add backlight ctrl for Lenovo Yoga Tab 3 Pro YT3-X90F 



The YT3 uses an TI LP8557 LED backlight controller, the LP8557's PWM input
is connected to a PWM output coming from the LCD panel's controller.

The Android kernel has a hack in the i915 driver to write the non-standard
DSI reg 0x51 with the desired level to set the duty-cycle of the LCD's PWM.

To avoid having to have a similar hack in the mainline kernel program
instantiate an i2c-client for the LP8557 with platform-data to have
the LP8557 to directly set the level (ignoring its PWM input), this allows
backlight brightness control through a backlight device registered by
the lp855x_bl driver.

Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230301092331.7038-13-hdegoede@redhat.com
parent 9b1d2662

drivers/platform/x86/x86-android-tablets/lenovo.c

+23 −0
Original line number Diff line number Diff line
@@ -346,6 +346,20 @@ static const struct software_node lenovo_yt3_hideep_ts_node = { 
	.properties = lenovo_yt3_hideep_ts_props,

};



/*

 * The YT3 uses an TI LP8557 LED backlight controller, the LP8557's PWM input is

 * connected to a PWM output coming from the LCD panel's controller. The Android

 * kernel has a hack in the i915 driver to write the non-standard DSI reg 0x51

 * with the desired level to set the duty-cycle of the LCD's PWM output.

 *

 * To avoid having to have a similar hack in the mainline kernel program the

 * LP8557 to directly set the level and use the lp855x_bl driver for control.

 */

static struct lp855x_platform_data lenovo_yt3_lp8557_pdata = {

	.device_control = 0x86,

	.initial_brightness = 128,

};



static const struct x86_i2c_client_info lenovo_yt3_i2c_clients[] __initconst = {

	{

		/* bq27500 fuel-gauge for the flat lipo battery behind the screen */
@@ -397,6 +411,15 @@ static const struct x86_i2c_client_info lenovo_yt3_i2c_clients[] __initconst = { 
			.trigger = ACPI_LEVEL_SENSITIVE,

			.polarity = ACPI_ACTIVE_LOW,

		},

	}, {

		/* LP8557 Backlight controller */

		.board_info = {

			.type = "lp8557",

			.addr = 0x2c,

			.dev_name = "lp8557",

			.platform_data = &lenovo_yt3_lp8557_pdata,

		},

		.adapter_path = "\\_SB_.PCI0.I2C1",

	}

};