Some shimmer/colorful points appears when using the steamOS color pipeline for HDR on gaming with DCN32. These points look like black values being wrongly mapped to red/blue/green values. It was caused because the number of hw points in regular LUTs and in a shaper LUT was treated as the same.
DCN3+ regular LUTs have 257 bases and implicit deltas (i.e. HW calculates them), but shaper LUT is a special case: it has 256 bases and 256 deltas, as in DCN1-2 regular LUTs, and outputs 14-bit values. Fix that by setting by decreasing in 1 the number of HW points computed in the LUT segmentation so that shaper LUT (i.e. fixpoint == true) keeps the same DCN10 CM logic and regular LUTs go with `hw_points + 1`. CC: Krunoslav Kovac <[email protected]> Fixes: 4d5fd3d08ea9 ("drm/amd/display: PQ tail accuracy") Signed-off-by: Melissa Wen <[email protected]> --- drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c index 0690c346f2c5..a4f14b16564c 100644 --- a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c +++ b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c @@ -163,6 +163,11 @@ bool cm3_helper_translate_curve_to_hw_format( hw_points += (1 << seg_distr[k]); } + // DCN3+ have 257 pts in lieu of no separate slope registers + // Prior HW had 256 base+slope pairs + // Shaper LUT (i.e. fixpoint == true) is still 256 bases and 256 deltas + hw_points = fixpoint ? (hw_points - 1) : hw_points; + j = 0; for (k = 0; k < (region_end - region_start); k++) { increment = NUMBER_SW_SEGMENTS / (1 << seg_distr[k]); @@ -223,8 +228,6 @@ bool cm3_helper_translate_curve_to_hw_format( corner_points[1].green.slope = dc_fixpt_zero; corner_points[1].blue.slope = dc_fixpt_zero; - // DCN3+ have 257 pts in lieu of no separate slope registers - // Prior HW had 256 base+slope pairs lut_params->hw_points_num = hw_points + 1; k = 0; -- 2.51.0
