For DRM legacy gamma, AMD display manager applies implicit sRGB degamma using a pre-defined sRGB transfer function. It works fine for DCN2 family where degamma ROM and custom curves go to the same color block. But, on DCN3+, degamma is split into two blocks: degamma ROM for pre-defined TFs and `gamma correction` for user/custom curves and degamma ROM settings doesn't apply to cursor plane. To get DRM legacy gamma working as expected, enable cursor degamma ROM for implict sRGB degamma on HW with this configuration. Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2803 Fixes: 96b020e2163f ("drm/amd/display: check attr flag before set cursor degamma on DCN3+") Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx> --- Hi, It seems that the previous color fix for atomic API brought out a difference in behavior of degamma color blocks between DCN2 and DCN3, as reported in the link. AFAIU, settings of the `degamma ROM` block for pre-defined TF doesn't apply to cursor plane. So, whenever we wants degamma ROM for cursor plane, we have to explicitly enable it using the attribute flag. This is the case when we do an implicit sRGB degamma to match DRM legacy gamma requirements. Another option would be changing the legacy gamma approach to use the `gamma correction` block where the pre-defined sRGB curve is calculated by AMD color module. I think that keeping degamma ROM usage on legacy gamma is better for performance, this is why I opted for this patch. But let me know if changing legacy gamma implementation in amdgpu_dm_color is better for consistence or any other thing to take into account. Thanks, Melissa drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c index 8eeca160d434..2aa7efd798e2 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c @@ -1269,6 +1269,13 @@ void amdgpu_dm_plane_handle_cursor_update(struct drm_plane *plane, attributes.rotation_angle = 0; attributes.attribute_flags.value = 0; + /* Enable cursor degamma ROM on DCN3+ for implicit sRGB degamma in DRM + * legacy gamma setup. + */ + if (crtc_state->cm_is_degamma_srgb && + adev->dm.dc->caps.color.dpp.gamma_corr) + attributes.attribute_flags.bits.ENABLE_CURSOR_DEGAMMA = 1; + attributes.pitch = afb->base.pitches[0] / afb->base.format->cpp[0]; if (crtc_state->stream) { -- 2.40.1
