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authorFelipe <Felipe.Clark@amd.com>2020-11-30 17:38:02 -0500
committerAlex Deucher <alexander.deucher@amd.com>2020-12-15 11:34:35 -0500
commite10777a67963163055f9ca43292cb21ff52967d2 (patch)
treeceec592831c016126820a86999806e0c52255b78
parent610c4974ad172dad884244763125f8cd6585c503 (diff)
drm/amd/display: Fix OGAM LUT calculation precision
[Why] The OGAM LUT precision was accumulating too much error in the higher end. [How] Instead of calculating all points of the LUT in relation to the previous ones, perform a full calculation in one of the intermediate segments to stop error propagation. Signed-off-by: Felipe Clark <Felipe.Clark@amd.com> Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com> Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
-rw-r--r--drivers/gpu/drm/amd/display/modules/color/color_gamma.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
index eced40a2fce4..5c67e12b2e55 100644
--- a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
+++ b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
@@ -30,6 +30,14 @@
#include "opp.h"
#include "color_gamma.h"
+/* When calculating LUT values the first region and at least one subsequent
+ * region are calculated with full precision. These defines are a demarcation
+ * of where the second region starts and ends.
+ * These are hardcoded values to avoid recalculating them in loops.
+ */
+#define PRECISE_LUT_REGION_START 224
+#define PRECISE_LUT_REGION_END 239
+
static struct hw_x_point coordinates_x[MAX_HW_POINTS + 2];
// these are helpers for calculations to reduce stack usage
@@ -346,7 +354,13 @@ static struct fixed31_32 translate_from_linear_space(
dc_fixpt_recip(args->gamma));
}
scratch_1 = dc_fixpt_add(one, args->a3);
- if (cal_buffer->buffer_index < 16)
+ /* In the first region (first 16 points) and in the
+ * region delimited by START/END we calculate with
+ * full precision to avoid error accumulation.
+ */
+ if ((cal_buffer->buffer_index >= PRECISE_LUT_REGION_START &&
+ cal_buffer->buffer_index <= PRECISE_LUT_REGION_END) ||
+ (cal_buffer->buffer_index < 16))
scratch_2 = dc_fixpt_pow(args->arg,
dc_fixpt_recip(args->gamma));
else
@@ -397,9 +411,7 @@ static struct fixed31_32 translate_from_linear_space_long(
dc_fixpt_recip(args->gamma))),
args->a2);
else
- return dc_fixpt_mul(
- args->arg,
- args->a1);
+ return dc_fixpt_mul(args->arg, args->a1);
}
static struct fixed31_32 calculate_gamma22(struct fixed31_32 arg, bool use_eetf, struct calculate_buffer *cal_buffer)
@@ -717,7 +729,6 @@ static struct fixed31_32 calculate_mapped_value(
BREAK_TO_DEBUGGER();
result = dc_fixpt_zero;
} else {
- BREAK_TO_DEBUGGER();
result = dc_fixpt_one;
}
@@ -976,6 +987,7 @@ static bool build_freesync_hdr(struct pwl_float_data_ex *rgb_regamma,
cal_buffer->buffer_index = 0; // see var definition for more info
rgb += 32; // first 32 points have problems with fixed point, too small
coord_x += 32;
+
for (i = 32; i <= hw_points_num; i++) {
if (!is_clipped) {
if (use_eetf) {