On Thu, Dec 7, 2023 at 9:47 AM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
>
> Mark reports that brightness is not restored after Xorg dpms screen blank.
>
> This behavior was introduced by commit d9e865826c20 ("drm/amd/display:
> Simplify brightness initialization") which dropped the cached backlight
> value in display code, but also removed code for when the default value
> read back was less than 1 nit.
>
> Restore this code so that the backlight brightness is restored to the
> correct default value in this circumstance.
>
> Reported-by: Mark Herbert <mark.herbert42@xxxxxxxxx>
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3031
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Camille Cho <camille.cho@xxxxxxx>
> Cc: Krunoslav Kovac <krunoslav.kovac@xxxxxxx>
> Cc: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> Fixes: d9e865826c20 ("drm/amd/display: Simplify brightness initialization")
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
> ---
> .../amd/display/dc/link/protocols/link_edp_panel_control.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
> index ac0fa88b52a0..bf53a86ea817 100644
> --- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
> +++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
> @@ -287,8 +287,8 @@ bool set_default_brightness_aux(struct dc_link *link)
> if (link && link->dpcd_sink_ext_caps.bits.oled == 1) {
> if (!read_default_bl_aux(link, &default_backlight))
> default_backlight = 150000;
> - // if > 5000, it might be wrong readback
> - if (default_backlight > 5000000)
> + // if < 1 nits or > 5000, it might be wrong readback
> + if (default_backlight < 1000 || default_backlight > 5000000)
> default_backlight = 150000;
>
> return edp_set_backlight_level_nits(link, true,
> --
> 2.34.1
>
