From: Sean Paul <[email protected]>

Fix a step discontinuity in the Post-CSC Gamma LUT when SDR dimming
is active by clamping Segment 2 to the last user-provided LUT entry
value instead of hardcoding it to 1.0 (1 << 24).

Link: 
https://lore.kernel.org/intel-gfx/[email protected]/ #v1
Signed-off-by: Sean Paul <[email protected]>

Changes in v2:
- Split out into separate patches for pre/post csc fixes
- Dropped loop bounds fix in favor of [1]

[1]- https://lore.kernel.org/r/[email protected]
---

Changes in v2.1:
- Rebased on Pranay's patch and sending without in-reply-to

 drivers/gpu/drm/i915/display/intel_color.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_color.c 
b/drivers/gpu/drm/i915/display/intel_color.c
index 7ef870cd9a16..7185f3628dcf 100644
--- a/drivers/gpu/drm/i915/display/intel_color.c
+++ b/drivers/gpu/drm/i915/display/intel_color.c
@@ -4038,11 +4038,11 @@ xelpd_program_plane_post_csc_lut(struct intel_dsb *dsb,
                                                   lut_val);
                        }
 
-                       /* Segment 2 */
+                       /* Segment 2 - clamp to the last LUT value to prevent 
step discontinuity */
                        do {
                                intel_de_write_dsb(display, dsb,
                                                   
PLANE_POST_CSC_GAMC_DATA_ENH(pipe, plane, 0),
-                                                  (1 << 24));
+                                                  lut_val);
                        } while (i++ < 34);
                } else {
                        /*TODO: Add for segment 0 */
-- 
Sean Paul, Software Engineer, Google / Chromium OS

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