drm/i915: keep backlight_enable on until turn eDP display off

This workaround is specific for a particular panel on Google
chromebook project. When user space daemon enter idle state.
It request adjust brightness to 0, turn backlight_enable signal
off and keep eDP main link active.

On general LCD, this behavior might not be a problem.
But on this panel, its tcon would expect source to execute
full eDP power off sequence after drop backlight_enable signal.
Without eDP power off sequence. Even source try to turn
backlight_enable signal on and restore proper brightness level.
This panel is not able to light on again.

This WA ignored the request from user space daemon to disable
backlight_enable signal and keep it on always. When user space
request kernel to turn eDP display off, kernel driver still
can control backlight_enable signal properly. It would not
impact standard eDP power off sequence.

v2: 1. modify the quirk name and debug messages.
    2. unregister backlight.power callback for specific device.
v3: 1. modify debug output messages.
    2. use DMI_EXACT_MATCH instead of DMI_MATCH.

Cc: Ville Syrjala <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Cooper Chiou <[email protected]>
Signed-off-by: Lee Shawn C <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

0 files changed, 0 insertions, 0 deletions