From: Sean Paul <[email protected]>

Fix two bugs in the plane-level color pipeline programming:
1. 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).
2. Fix a typo in the loop condition in xelpd_program_plane_pre_csc_lut
   for Segment 2 degamma programming, changing 'while (i++ > 130)' to
   'while (i++ < 130)'. Also clamp Segment 2 to the last user-provided
   LUT entry value instead of hardcoding it to 1.0 (1 << 24) to fix
   a step discontinuity similar to the Post-CSC fix.

Signed-off-by: Sean Paul <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_color.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_color.c 
b/drivers/gpu/drm/i915/display/intel_color.c
index 2d318e922671..9b807b024ec3 100644
--- a/drivers/gpu/drm/i915/display/intel_color.c
+++ b/drivers/gpu/drm/i915/display/intel_color.c
@@ -3953,6 +3953,7 @@ xelpd_program_plane_pre_csc_lut(struct intel_dsb *dsb,
        enum plane_id plane = to_intel_plane(state->plane)->id;
        const struct drm_color_lut32 *pre_csc_lut = 
plane_state->hw.degamma_lut->data;
        u32 i, lut_size;
+       u32 lut_val = 1 << 24;
 
        if (icl_is_hdr_plane(display, plane)) {
                lut_size = 128;
@@ -3963,7 +3964,7 @@ xelpd_program_plane_pre_csc_lut(struct intel_dsb *dsb,
 
                if (pre_csc_lut) {
                        for (i = 0; i < lut_size; i++) {
-                               u32 lut_val = 
drm_color_lut32_extract(pre_csc_lut[i].green, 24);
+                               lut_val = 
drm_color_lut32_extract(pre_csc_lut[i].green, 24);
 
                                intel_de_write_dsb(display, dsb,
                                                   
PLANE_PRE_CSC_GAMC_DATA_ENH(pipe, plane, 0),
@@ -3975,8 +3976,8 @@ xelpd_program_plane_pre_csc_lut(struct intel_dsb *dsb,
                        do {
                                intel_de_write_dsb(display, dsb,
                                                   
PLANE_PRE_CSC_GAMC_DATA_ENH(pipe, plane, 0),
-                                                  (1 << 24));
-                       } while (i++ > 130);
+                                                  lut_val);
+                       } while (i++ < 130);
                } else {
                        for (i = 0; i < lut_size; i++) {
                                u32 v = (i * ((1 << 24) - 1)) / (lut_size - 1);
@@ -4023,11 +4024,11 @@ 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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