drm/radeon: Bypass hw lut's for > 8 bpc framebuffer scanout.
The hardware lut's only have 256 slots for indexing by a
8 bpc framebuffer. In 10 bpc scanout modes, framebuffer
color values would get truncated to their 8 msb's,
thereby losing the extra precision afforded by a 10 bpc
framebuffer.
To retain full precision, bypass the hw lut in 10 bpc
scanout mode.
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
index b91f79e..9758f91 100644
--- a/drivers/gpu/drm/radeon/atombios_crtc.c
+++ b/drivers/gpu/drm/radeon/atombios_crtc.c
@@ -1136,6 +1136,7 @@
u32 fb_swap = EVERGREEN_GRPH_ENDIAN_SWAP(EVERGREEN_GRPH_ENDIAN_NONE);
u32 tmp, viewport_w, viewport_h;
int r;
+ bool bypass_lut = false;
/* no fb bound */
if (!atomic && !crtc->primary->fb) {
@@ -1225,6 +1226,8 @@
#ifdef __BIG_ENDIAN
fb_swap = EVERGREEN_GRPH_ENDIAN_SWAP(EVERGREEN_GRPH_ENDIAN_8IN32);
#endif
+ /* Greater 8 bpc fb needs to bypass hw-lut to retain precision */
+ bypass_lut = true;
break;
case DRM_FORMAT_BGRX1010102:
case DRM_FORMAT_BGRA1010102:
@@ -1233,6 +1236,8 @@
#ifdef __BIG_ENDIAN
fb_swap = EVERGREEN_GRPH_ENDIAN_SWAP(EVERGREEN_GRPH_ENDIAN_8IN32);
#endif
+ /* Greater 8 bpc fb needs to bypass hw-lut to retain precision */
+ bypass_lut = true;
break;
default:
DRM_ERROR("Unsupported screen format %s\n",
@@ -1365,6 +1370,18 @@
WREG32(EVERGREEN_GRPH_CONTROL + radeon_crtc->crtc_offset, fb_format);
WREG32(EVERGREEN_GRPH_SWAP_CONTROL + radeon_crtc->crtc_offset, fb_swap);
+ /*
+ * The LUT only has 256 slots for indexing by a 8 bpc fb. Bypass the LUT
+ * for > 8 bpc scanout to avoid truncation of fb indices to 8 msb's, to
+ * retain the full precision throughout the pipeline.
+ */
+ WREG32_P(EVERGREEN_GRPH_LUT_10BIT_BYPASS_CONTROL + radeon_crtc->crtc_offset,
+ (bypass_lut ? EVERGREEN_LUT_10BIT_BYPASS_EN : 0),
+ ~EVERGREEN_LUT_10BIT_BYPASS_EN);
+
+ if (bypass_lut)
+ DRM_DEBUG_KMS("Bypassing hardware LUT due to 10 bit fb scanout.\n");
+
WREG32(EVERGREEN_GRPH_SURFACE_OFFSET_X + radeon_crtc->crtc_offset, 0);
WREG32(EVERGREEN_GRPH_SURFACE_OFFSET_Y + radeon_crtc->crtc_offset, 0);
WREG32(EVERGREEN_GRPH_X_START + radeon_crtc->crtc_offset, 0);
@@ -1432,6 +1449,7 @@
u32 fb_swap = R600_D1GRPH_SWAP_ENDIAN_NONE;
u32 tmp, viewport_w, viewport_h;
int r;
+ bool bypass_lut = false;
/* no fb bound */
if (!atomic && !crtc->primary->fb) {
@@ -1517,6 +1535,8 @@
#ifdef __BIG_ENDIAN
fb_swap = R600_D1GRPH_SWAP_ENDIAN_32BIT;
#endif
+ /* Greater 8 bpc fb needs to bypass hw-lut to retain precision */
+ bypass_lut = true;
break;
default:
DRM_ERROR("Unsupported screen format %s\n",
@@ -1559,6 +1579,13 @@
if (rdev->family >= CHIP_R600)
WREG32(R600_D1GRPH_SWAP_CONTROL + radeon_crtc->crtc_offset, fb_swap);
+ /* LUT only has 256 slots for 8 bpc fb. Bypass for > 8 bpc scanout for precision */
+ WREG32_P(AVIVO_D1GRPH_LUT_SEL + radeon_crtc->crtc_offset,
+ (bypass_lut ? AVIVO_LUT_10BIT_BYPASS_EN : 0), ~AVIVO_LUT_10BIT_BYPASS_EN);
+
+ if (bypass_lut)
+ DRM_DEBUG_KMS("Bypassing hardware LUT due to 10 bit fb scanout.\n");
+
WREG32(AVIVO_D1GRPH_SURFACE_OFFSET_X + radeon_crtc->crtc_offset, 0);
WREG32(AVIVO_D1GRPH_SURFACE_OFFSET_Y + radeon_crtc->crtc_offset, 0);
WREG32(AVIVO_D1GRPH_X_START + radeon_crtc->crtc_offset, 0);