From: Alex Deucher alexander.deucher@amd.com

[ Upstream commit f2ad3accefc63e72e9932e141c21875cc04beec8 ]

We've gotten a number of reports about backlight control not working on panels which indicate that they use aux backlight control. A recent patch:

commit 2d73eabe2984a435737498ab39bb1500a9ffe9a9 Author: Camille Cho Camille.Cho@amd.com Date: Thu Jul 8 18:28:37 2021 +0800

drm/amd/display: Only set default brightness for OLED

[Why] We used to unconditionally set backlight path as AUX for panels capable of backlight adjustment via DPCD in set default brightness.

[How] This should be limited to OLED panel only since we control backlight via PWM path for SDR mode in LCD HDR panel.

Reviewed-by: Krunoslav Kovac krunoslav.kovac@amd.com Acked-by: Rodrigo Siqueira Rodrigo.Siqueira@amd.com Signed-off-by: Camille Cho Camille.Cho@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com

Changes some other code to only use aux for backlight control on OLED panels. The commit message seems to indicate that PWM should be used for SDR mode on HDR panels. Do something similar for backlight control in general. This may need to be revisited if and when HDR started to get used.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1438 Bug: https://bugzilla.kernel.org/show_bug.cgi?id=213715 Reviewed-by: Roman Li Roman.Li@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 6eb308670f48..8d537123e4ad 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -2162,9 +2162,9 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector) max_cll = conn_base->hdr_sink_metadata.hdmi_type1.max_cll; min_cll = conn_base->hdr_sink_metadata.hdmi_type1.min_cll;

- if (caps->ext_caps->bits.oled == 1 || + if (caps->ext_caps->bits.oled == 1 /*|| caps->ext_caps->bits.sdr_aux_backlight_control == 1 || - caps->ext_caps->bits.hdr_aux_backlight_control == 1) + caps->ext_caps->bits.hdr_aux_backlight_control == 1*/) caps->aux_support = true;

if (amdgpu_backlight == 0)