drm/i915/display: Prevent double YUV range correction on HDR planes

Prevent the ICL HDR plane pipeline from performing YUV color range
correction twice when the input is in limited range. This is done by
removing the limited-range code from icl_program_input_csc().

Before this patch the following could happen: user space gives us a YUV
buffer in limited range; per the pipeline in [1], the plane would first
go through a "YUV Range correct" stage that expands the range; the plane
would then go through the "Input CSC" stage which would also expand the
range because icl_program_input_csc() would use a matrix and an offset
that assume limited-range input; this would ultimately cause dark and
light colors to appear darker and lighter than they should respectively.

This is an issue because if a buffer switches between being scanned out
and being composited with the GPU, the user will see a color difference.
If this switching happens quickly and frequently, the user will perceive
this as a flickering.

[1] https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-icllp-vol12-displayengine_0.pdf#page=281

Cc: [email protected]
Signed-off-by: Andres Calderon Jaramillo <[email protected]>
Signed-off-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index ad1187e50665..2c7931b1cf0d 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -3584,6 +3584,8 @@ u32 glk_plane_color_ctl(const struct intel_crtc_state *crtc_state,
 			plane_color_ctl |= PLANE_COLOR_YUV_RANGE_CORRECTION_DISABLE;
 	} else if (fb->format->is_yuv) {
 		plane_color_ctl |= PLANE_COLOR_INPUT_CSC_ENABLE;
+		if (plane_state->hw.color_range == DRM_COLOR_YCBCR_FULL_RANGE)
+			plane_color_ctl |= PLANE_COLOR_YUV_RANGE_CORRECTION_DISABLE;
 	}
 
 	return plane_color_ctl;