drm/amd/display: Optimize regamma calculations

There are several optimizations:
1) Use predefined SRGB, don't calculate. This is the most common case.
2) Precompute HW X points at boot since they're fixed in ColModule
3) Precompute PQ - it never changes and is very CPU intensive in fixed pt.
4) Reduce number of points in ColModule to 512 (32x16) from 1024. This also
requires reducing some regions for legacy DCEs to 16 pts at most.

Performance
1) is super-fast, build_output_tf is 1-2us, down from 25000-30000.
Programming also fast since only one reg write.
2)+3) gives build_output_tf for PQ in ~100us range, down from ~80000-110000
2) + 4) results in slightly over 50% improvement. It gives an idea of the
savings when we can't use SRGB or PQ table (e.g. sdr white level > 80).

There's also a bit of refactoring: renaming some stuff that was misleading
and removing a lot of magic numbers that novices might not be able to
understand where they come from and what they mean.

Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 21 insertions, 18 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
index 53ba3600ee6a..b3db6397d353 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c
@@ -232,10 +232,11 @@ bool cm_helper_convert_to_custom_float(
 	return true;
 }
 
-
+/* driver uses 32 regions or less, but DCN HW has 34, extra 2 are set to 0 */
 #define MAX_REGIONS_NUMBER 34
 #define MAX_LOW_POINT      25
-#define NUMBER_SEGMENTS    32
+#define NUMBER_REGIONS     32
+#define NUMBER_SW_SEGMENTS 16
 
 bool cm_helper_translate_curve_to_hw_format(
 				const struct dc_transfer_func *output_tf,
@@ -251,7 +252,7 @@ bool cm_helper_translate_curve_to_hw_format(
 	struct fixed31_32 y1_min;
 	struct fixed31_32 y3_max;
 
-	int32_t segment_start, segment_end;
+	int32_t region_start, region_end;
 	int32_t i;
 	uint32_t j, k, seg_distr[MAX_REGIONS_NUMBER], increment, start_index, hw_points;
 
@@ -271,11 +272,11 @@ bool cm_helper_translate_curve_to_hw_format(
 		/* 32 segments
 		 * segments are from 2^-25 to 2^7
 		 */
-		for (i = 0; i < 32 ; i++)
+		for (i = 0; i < NUMBER_REGIONS ; i++)
 			seg_distr[i] = 3;
 
-		segment_start = -25;
-		segment_end   = 7;
+		region_start = -MAX_LOW_POINT;
+		region_end   = NUMBER_REGIONS - MAX_LOW_POINT;
 	} else {
 		/* 10 segments
 		 * segment is from 2^-10 to 2^0
@@ -289,14 +290,14 @@ bool cm_helper_translate_curve_to_hw_format(
 		seg_distr[5] = 4;
 		seg_distr[6] = 4;
 		seg_distr[7] = 4;
-		seg_distr[8] = 5;
-		seg_distr[9] = 5;
+		seg_distr[8] = 4;
+		seg_distr[9] = 4;
 
-		segment_start = -10;
-		segment_end = 0;
+		region_start = -10;
+		region_end = 0;
 	}
 
-	for (i = segment_end - segment_start; i < MAX_REGIONS_NUMBER ; i++)
+	for (i = region_end - region_start; i < MAX_REGIONS_NUMBER ; i++)
 		seg_distr[i] = -1;
 
 	for (k = 0; k < MAX_REGIONS_NUMBER; k++) {
@@ -305,10 +306,12 @@ bool cm_helper_translate_curve_to_hw_format(
 	}
 
 	j = 0;
-	for (k = 0; k < (segment_end - segment_start); k++) {
-		increment = NUMBER_SEGMENTS / (1 << seg_distr[k]);
-		start_index = (segment_start + k + MAX_LOW_POINT) * NUMBER_SEGMENTS;
-		for (i = start_index; i < start_index + NUMBER_SEGMENTS; i += increment) {
+	for (k = 0; k < (region_end - region_start); k++) {
+		increment = NUMBER_SW_SEGMENTS / (1 << seg_distr[k]);
+		start_index = (region_start + k + MAX_LOW_POINT) *
+				NUMBER_SW_SEGMENTS;
+		for (i = start_index; i < start_index + NUMBER_SW_SEGMENTS;
+				i += increment) {
 			if (j == hw_points - 1)
 				break;
 			rgb_resulted[j].red = output_tf->tf_pts.red[i];
@@ -319,15 +322,15 @@ bool cm_helper_translate_curve_to_hw_format(
 	}
 
 	/* last point */
-	start_index = (segment_end + MAX_LOW_POINT) * NUMBER_SEGMENTS;
+	start_index = (region_end + MAX_LOW_POINT) * NUMBER_SW_SEGMENTS;
 	rgb_resulted[hw_points - 1].red = output_tf->tf_pts.red[start_index];
 	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];
 
 	arr_points[0].x = dal_fixed31_32_pow(dal_fixed31_32_from_int(2),
-					     dal_fixed31_32_from_int(segment_start));
+					     dal_fixed31_32_from_int(region_start));
 	arr_points[1].x = dal_fixed31_32_pow(dal_fixed31_32_from_int(2),
-					     dal_fixed31_32_from_int(segment_end));
+					     dal_fixed31_32_from_int(region_end));
 
 	y_r = rgb_resulted[0].red;
 	y_g = rgb_resulted[0].green;