From: "Leo (Sunpeng) Li" <sunpeng.li@xxxxxxx>
DRM's documentation for the color transform matrix does not specify
whether the values are in signed-magnitude, or 2's complement.
Therefore, it was assumed to use 2's complement.
However, existing usermode implementations use signed-magnitude.
Therefore, conform to existing standards, and convert to 2's complement
internally.
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland at amd.com>
---
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
index e845c511656e..f6cb502c303f 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
@@ -193,6 +193,7 @@ void amdgpu_dm_set_ctm(struct dm_crtc_state *crtc)
struct drm_property_blob *blob = crtc->base.ctm;
struct dc_stream_state *stream = crtc->stream;
struct drm_color_ctm *ctm;
+ int64_t val;
int i;
if (!blob) {
@@ -206,7 +207,9 @@ void amdgpu_dm_set_ctm(struct dm_crtc_state *crtc)
* DRM gives a 3x3 matrix, but DC wants 3x4. Assuming we're operating
* with homogeneous coordinates, augment the matrix with 0's.
*
- * The format provided is S31.32, which is the same as our fixed31_32.
+ * The format provided is S31.32, using signed-magnitude representation.
+ * Our fixed31_32 is also S31.32, but is using 2's complement. We have
+ * to convert from signed-magnitude to 2's complement.
*/
for (i = 0; i < 12; i++) {
/* Skip 4th element */
@@ -214,8 +217,14 @@ void amdgpu_dm_set_ctm(struct dm_crtc_state *crtc)
stream->gamut_remap_matrix.matrix[i] = dal_fixed31_32_zero;
continue;
}
- /* csc[i] = ctm[i - floor(i/4)] */
- stream->gamut_remap_matrix.matrix[i].value = ctm->matrix[i - (i/4)];
+
+ /* gamut_remap_matrix[i] = ctm[i - floor(i/4)] */
+ val = ctm->matrix[i - (i/4)];
+ /* If negative, convert to 2's complement. */
+ if (val & (1ULL << 63))
+ val = -(val & ~(1ULL << 63));
+
+ stream->gamut_remap_matrix.matrix[i].value = val;
}
}
--
2.14.1
