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

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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: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230301092331.7038-13-hdegoede@redhat.com
This commit is contained in:
Hans de Goede 2023-02-22 22:42:26 +01:00
parent 9b1d2662b8
commit 607fbac0fc
1 changed files with 23 additions and 0 deletions
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23
drivers/platform/x86/x86-android-tablets/lenovo.c
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@ -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",
}
};