[PATCH 5.10 023/157] drm/amd/display: Correct algorithm for reversed gamma

Greg Kroah-Hartman
2021-03-22T12:41:57Z

From: Calvin Hou <Calvin.Hou@amd.com>

commit 34fa493a565cc6fcee6919787c11e264f55603c6 upstream.

[Why]
DCN30 needs to correctly program reversed gamma curve, which DCN20
already has.
Also needs to fix a bug that 252-255 values are clipped.

[How]
Apply two fixes into DCN30.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1513
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Calvin Hou <Calvin.Hou@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Acked-by: Vladimir Stempen <Vladimir.Stempen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c | 26 +++++++++++------
1 file changed, 18 insertions(+), 8 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_cm_common.c
@@ -113,6 +113,7 @@ bool cm3_helper_translate_curve_to_hw_fo
struct pwl_result_data *rgb_resulted;
struct pwl_result_data *rgb;
struct pwl_result_data *rgb_plus_1;
+ struct pwl_result_data *rgb_minus_1;
struct fixed31_32 end_value;

int32_t region_start, region_end;
@@ -140,7 +141,7 @@ bool cm3_helper_translate_curve_to_hw_fo
region_start = -MAX_LOW_POINT;
region_end = NUMBER_REGIONS - MAX_LOW_POINT;
} else {
- /* 10 segments
+ /* 11 segments
* segment is from 2^-10 to 2^0
* There are less than 256 points, for optimization
*/
@@ -154,9 +155,10 @@ bool cm3_helper_translate_curve_to_hw_fo
seg_distr[7] = 4;
seg_distr[8] = 4;
seg_distr[9] = 4;
+ seg_distr[10] = 1;

region_start = -10;
- region_end = 0;
+ region_end = 1;
}

for (i = region_end - region_start; i < MAX_REGIONS_NUMBER ; i++)
@@ -189,6 +191,10 @@ bool cm3_helper_translate_curve_to_hw_fo
rgb_resulted[hw_points - 1].green = output_tf->tf_pts.green[start_index];
rgb_resulted[hw_points - 1].blue = output_tf->tf_pts.blue[start_index];

+ rgb_resulted[hw_points].red = rgb_resulted[hw_points - 1].red;
+ rgb_resulted[hw_points].green = rgb_resulted[hw_points - 1].green;
+ rgb_resulted[hw_points].blue = rgb_resulted[hw_points - 1].blue;
+
// All 3 color channels have same x
corner_points[0].red.x = dc_fixpt_pow(dc_fixpt_from_int(2),
dc_fixpt_from_int(region_start));
@@ -259,15 +265,18 @@ bool cm3_helper_translate_curve_to_hw_fo

rgb = rgb_resulted;
rgb_plus_1 = rgb_resulted + 1;
+ rgb_minus_1 = rgb;

i = 1;
while (i != hw_points + 1) {
- if (dc_fixpt_lt(rgb_plus_1->red, rgb->red))
- rgb_plus_1->red = rgb->red;
- if (dc_fixpt_lt(rgb_plus_1->green, rgb->green))
- rgb_plus_1->green = rgb->green;
- if (dc_fixpt_lt(rgb_plus_1->blue, rgb->blue))
- rgb_plus_1->blue = rgb->blue;
+ if (i >= hw_points - 1) {
+ if (dc_fixpt_lt(rgb_plus_1->red, rgb->red))
+ rgb_plus_1->red = dc_fixpt_add(rgb->red, rgb_minus_1->delta_red);
+ if (dc_fixpt_lt(rgb_plus_1->green, rgb->green))
+ rgb_plus_1->green = dc_fixpt_add(rgb->green, rgb_minus_1->delta_green);
+ if (dc_fixpt_lt(rgb_plus_1->blue, rgb->blue))
+ rgb_plus_1->blue = dc_fixpt_add(rgb->blue, rgb_minus_1->delta_blue);
+ }

rgb->delta_red = dc_fixpt_sub(rgb_plus_1->red, rgb->red);
rgb->delta_green = dc_fixpt_sub(rgb_plus_1->green, rgb->green);
@@ -283,6 +292,7 @@ bool cm3_helper_translate_curve_to_hw_fo
}

++rgb_plus_1;
+ rgb_minus_1 = rgb;
++rgb;
++i;
}