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drm/radeon: Bypass hw lut's for > 8 bpc framebuffer scanout.
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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>
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Mario Kleiner authored and Alex Deucher committed Jun 13, 2014
1 parent 8bae427 commit 4366f3b
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Showing 4 changed files with 32 additions and 1 deletion.
27 changes: 27 additions & 0 deletions drivers/gpu/drm/radeon/atombios_crtc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1136,6 +1136,7 @@ static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
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) {
Expand Down Expand Up @@ -1225,6 +1226,8 @@ static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
#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:
Expand All @@ -1233,6 +1236,8 @@ static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
#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",
Expand Down Expand Up @@ -1365,6 +1370,18 @@ static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
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);
Expand Down Expand Up @@ -1432,6 +1449,7 @@ static int avivo_crtc_do_set_base(struct drm_crtc *crtc,
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) {
Expand Down Expand Up @@ -1517,6 +1535,8 @@ static int avivo_crtc_do_set_base(struct drm_crtc *crtc,
#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",
Expand Down Expand Up @@ -1559,6 +1579,13 @@ static int avivo_crtc_do_set_base(struct drm_crtc *crtc,
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);
Expand Down
2 changes: 2 additions & 0 deletions drivers/gpu/drm/radeon/evergreen_reg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,8 @@
# define EVERGREEN_GRPH_ARRAY_LINEAR_ALIGNED 1
# define EVERGREEN_GRPH_ARRAY_1D_TILED_THIN1 2
# define EVERGREEN_GRPH_ARRAY_2D_TILED_THIN1 4
#define EVERGREEN_GRPH_LUT_10BIT_BYPASS_CONTROL 0x6808
# define EVERGREEN_LUT_10BIT_BYPASS_EN (1 << 8)
#define EVERGREEN_GRPH_SWAP_CONTROL 0x680c
# define EVERGREEN_GRPH_ENDIAN_SWAP(x) (((x) & 0x3) << 0)
# define EVERGREEN_GRPH_ENDIAN_NONE 0
Expand Down
1 change: 1 addition & 0 deletions drivers/gpu/drm/radeon/r500_reg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -402,6 +402,7 @@
* block and vice versa. This applies to GRPH, CUR, etc.
*/
#define AVIVO_D1GRPH_LUT_SEL 0x6108
# define AVIVO_LUT_10BIT_BYPASS_EN (1 << 8)
#define AVIVO_D1GRPH_PRIMARY_SURFACE_ADDRESS 0x6110
#define R700_D1GRPH_PRIMARY_SURFACE_ADDRESS_HIGH 0x6914
#define R700_D2GRPH_PRIMARY_SURFACE_ADDRESS_HIGH 0x6114
Expand Down
3 changes: 2 additions & 1 deletion drivers/gpu/drm/radeon/radeon_display.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,8 @@ static void avivo_crtc_load_lut(struct drm_crtc *crtc)
(radeon_crtc->lut_b[i] << 0));
}

WREG32(AVIVO_D1GRPH_LUT_SEL + radeon_crtc->crtc_offset, radeon_crtc->crtc_id);
/* Only change bit 0 of LUT_SEL, other bits are set elsewhere */
WREG32_P(AVIVO_D1GRPH_LUT_SEL + radeon_crtc->crtc_offset, radeon_crtc->crtc_id, ~1);
}

static void dce4_crtc_load_lut(struct drm_crtc *crtc)
Expand Down

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