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authorLeo (Sunpeng) Li <sunpeng.li@amd.com>2018-04-03 16:07:16 -0400
committerAlex Deucher <alexander.deucher@amd.com>2018-04-12 13:56:21 -0500
commitb2f3f5920ddb5b121cbc57ee9efc0c1ffe4d19af (patch)
tree7c3ac77552268f65a03c214c12864a67bda1d013 /drivers/gpu
parent1409bc6b2bff44ea4e366b892dcac4a1cf0a5e8b (diff)
downloadlinux-b2f3f5920ddb5b121cbc57ee9efc0c1ffe4d19af.tar.bz2
drm/amd/display: Fix regamma not affecting full-intensity color values
Hardware understands the regamma LUT as a piecewise linear function, with points spaced exponentially along the range. We previously programmed the LUT for range [2^-10, 2^0). This causes (normalized) color values of 1 (=2^0) to miss the programmed LUT, and fall onto the end region. For DCE, the end region is extrapolated using a single (base, slope) pair, using the max y-value from the last point in the curve as base. This presents a problem, since this value affects all three color channels. Scaling down the intensity of say - the blue regamma curve - will not affect it's end region. This is especially noticiable when using RedShift. It scales down the blue and green channels, but leaves full-intensity colors unshifted. Therefore, extend the range to cover [2^-10, 2^1) by programming another hardware segment, containing only one point. That way, we won't be hitting the end region. Note that things are a bit different for DCN, since the end region can be set per-channel. Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com> Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com> Acked-by: Harry Wentland <harry.wentland@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
index 1c644c7a24b7..d0575999f172 100644
--- a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
@@ -453,10 +453,13 @@ dce110_translate_regamma_to_hw_format(const struct dc_transfer_func *output_tf,
} else {
/* 10 segments
- * segment is from 2^-10 to 2^0
+ * segment is from 2^-10 to 2^1
+ * We include an extra segment for range [2^0, 2^1). This is to
+ * ensure that colors with normalized values of 1 don't miss the
+ * LUT.
*/
region_start = -10;
- region_end = 0;
+ region_end = 1;
seg_distr[0] = 4;
seg_distr[1] = 4;
@@ -468,7 +471,7 @@ dce110_translate_regamma_to_hw_format(const struct dc_transfer_func *output_tf,
seg_distr[7] = 4;
seg_distr[8] = 4;
seg_distr[9] = 4;
- seg_distr[10] = -1;
+ seg_distr[10] = 0;
seg_distr[11] = -1;
seg_distr[12] = -1;
seg_distr[13] = -1;