Re: [PATCH v2 01/34] drm/amd/display: fix segment distribution for linear LUTs
From: Harry Wentland
Date: Fri Sep 08 2023 - 10:40:20 EST
On 2023-09-08 10:11, Melissa Wen wrote:
On 09/06, Harry Wentland wrote:
On 2023-08-10 12:02, Melissa Wen wrote:
From: Harry Wentland <harry.wentland@xxxxxxx>
The region and segment calculation was incapable of dealing
with regions of more than 16 segments. We first fix this.
Now that we can support regions up to 256 elements we can
define a better segment distribution for near-linear LUTs
for our maximum of 256 HW-supported points.
With these changes an "identity" LUT looks visually
indistinguishable from bypass and allows us to use
our 3DLUT.
Have you had a chance to test whether this patch makes a
difference? I haven't had the time yet.
Last time I tested there was a banding issue on plane shaper LUT PQ ->
Display Native, but it seems I don't have this use case on tester
anymore, so I wasn't able to double-check if the issue persist. Maybe
Joshua can provide some inputs here.
Something I noticed is that shaper LUTs are the only 1D LUT on DCN30
pipeline that uses cm_helper_translate_curve_to_hw_format(), all others
(dpp-degamma/dpp-blend/mpc-regamma) call cm3_helper_translate_curve_*.
Yeah, they use different codepaths, unfortunately. Might be nice if we
could make them use the same.
We can drop it from this series until we get the steps to report the
issue properly.
Thanks. If you have concrete steps that show the issue (or even better,
an IGT test) I would be happy to include this.
Harry
Melissa
Harry
Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx>
---
.../amd/display/dc/dcn10/dcn10_cm_common.c | 93 +++++++++++++++----
1 file changed, 75 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 3538973bd0c6..04b2e04b68f3 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
@@ -349,20 +349,37 @@ bool cm_helper_translate_curve_to_hw_format(struct dc_context *ctx,
* segment is from 2^-10 to 2^1
* There are less than 256 points, for optimization
*/
- seg_distr[0] = 3;
- seg_distr[1] = 4;
- seg_distr[2] = 4;
- seg_distr[3] = 4;
- seg_distr[4] = 4;
- seg_distr[5] = 4;
- seg_distr[6] = 4;
- seg_distr[7] = 4;
- seg_distr[8] = 4;
- seg_distr[9] = 4;
- seg_distr[10] = 1;
+ if (output_tf->tf == TRANSFER_FUNCTION_LINEAR) {
+ seg_distr[0] = 0; /* 2 */
+ seg_distr[1] = 1; /* 4 */
+ seg_distr[2] = 2; /* 4 */
+ seg_distr[3] = 3; /* 8 */
+ seg_distr[4] = 4; /* 16 */
+ seg_distr[5] = 5; /* 32 */
+ seg_distr[6] = 6; /* 64 */
+ seg_distr[7] = 7; /* 128 */
+
+ region_start = -8;
+ region_end = 1;
+ } else {
+ seg_distr[0] = 3; /* 8 */
+ seg_distr[1] = 4; /* 16 */
+ seg_distr[2] = 4;
+ seg_distr[3] = 4;
+ seg_distr[4] = 4;
+ seg_distr[5] = 4;
+ seg_distr[6] = 4;
+ seg_distr[7] = 4;
+ seg_distr[8] = 4;
+ seg_distr[9] = 4;
+ seg_distr[10] = 1; /* 2 */
+ /* total = 8*16 + 8 + 64 + 2 = */
+
+ region_start = -10;
+ region_end = 1;
+ }
+
- region_start = -10;
- region_end = 1;
}
for (i = region_end - region_start; i < MAX_REGIONS_NUMBER ; i++)
@@ -375,16 +392,56 @@ bool cm_helper_translate_curve_to_hw_format(struct dc_context *ctx,
j = 0;
for (k = 0; k < (region_end - region_start); k++) {
- increment = NUMBER_SW_SEGMENTS / (1 << seg_distr[k]);
+ /*
+ * We're using an ugly-ish hack here. Our HW allows for
+ * 256 segments per region but SW_SEGMENTS is 16.
+ * SW_SEGMENTS has some undocumented relationship to
+ * the number of points in the tf_pts struct, which
+ * is 512, unlike what's suggested TRANSFER_FUNC_POINTS.
+ *
+ * In order to work past this dilemma we'll scale our
+ * increment by (1 << 4) and then do the inverse (1 >> 4)
+ * when accessing the elements in tf_pts.
+ *
+ * TODO: find a better way using SW_SEGMENTS and
+ * TRANSFER_FUNC_POINTS definitions
+ */
+ increment = (NUMBER_SW_SEGMENTS << 4) / (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;
+ for (i = (start_index << 4); i < (start_index << 4) + (NUMBER_SW_SEGMENTS << 4);
i += increment) {
+ struct fixed31_32 in_plus_one, in;
+ struct fixed31_32 value, red_value, green_value, blue_value;
+ uint32_t t = i & 0xf;
+
if (j == hw_points - 1)
break;
- rgb_resulted[j].red = output_tf->tf_pts.red[i];
- rgb_resulted[j].green = output_tf->tf_pts.green[i];
- rgb_resulted[j].blue = output_tf->tf_pts.blue[i];
+
+ in_plus_one = output_tf->tf_pts.red[(i >> 4) + 1];
+ in = output_tf->tf_pts.red[i >> 4];
+ value = dc_fixpt_sub(in_plus_one, in);
+ value = dc_fixpt_shr(dc_fixpt_mul_int(value, t), 4);
+ value = dc_fixpt_add(in, value);
+ red_value = value;
+
+ in_plus_one = output_tf->tf_pts.green[(i >> 4) + 1];
+ in = output_tf->tf_pts.green[i >> 4];
+ value = dc_fixpt_sub(in_plus_one, in);
+ value = dc_fixpt_shr(dc_fixpt_mul_int(value, t), 4);
+ value = dc_fixpt_add(in, value);
+ green_value = value;
+
+ in_plus_one = output_tf->tf_pts.blue[(i >> 4) + 1];
+ in = output_tf->tf_pts.blue[i >> 4];
+ value = dc_fixpt_sub(in_plus_one, in);
+ value = dc_fixpt_shr(dc_fixpt_mul_int(value, t), 4);
+ value = dc_fixpt_add(in, value);
+ blue_value = value;
+
+ rgb_resulted[j].red = red_value;
+ rgb_resulted[j].green = green_value;
+ rgb_resulted[j].blue = blue_value;
j++;
}
}