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drm/i915/display: Prevent double YUV range correction on HDR planes
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commit 00f9a08 upstream.

Prevent the ICL HDR plane pipeline from performing YUV color range
correction twice when the input is in limited range. This is done by
removing the limited-range code from icl_program_input_csc().

Before this patch the following could happen: user space gives us a YUV
buffer in limited range; per the pipeline in [1], the plane would first
go through a "YUV Range correct" stage that expands the range; the plane
would then go through the "Input CSC" stage which would also expand the
range because icl_program_input_csc() would use a matrix and an offset
that assume limited-range input; this would ultimately cause dark and
light colors to appear darker and lighter than they should respectively.

This is an issue because if a buffer switches between being scanned out
and being composited with the GPU, the user will see a color difference.
If this switching happens quickly and frequently, the user will perceive
this as a flickering.

[1] https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-icllp-vol12-displayengine_0.pdf#page=281

Cc: stable@vger.kernel.org
Signed-off-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215224219.3896256-1-andrescj@google.com
(cherry picked from commit fed3875)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210202084553.30691-1-ville.syrjala@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@andrescj-chromium @gregkh
andrescj-chromium authored and gregkh committed Feb 10, 2021
1 parent 2545b18 commit 1f27c73
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Showing 2 changed files with 12 additions and 55 deletions.
2 changes: 2 additions & 0 deletions drivers/gpu/drm/i915/display/intel_display.c
View file
Expand Up @@ -4880,6 +4880,8 @@ u32 glk_plane_color_ctl(const struct intel_crtc_state *crtc_state,
plane_color_ctl |= PLANE_COLOR_YUV_RANGE_CORRECTION_DISABLE;
} else if (fb->format->is_yuv) {
plane_color_ctl |= PLANE_COLOR_INPUT_CSC_ENABLE;
if (plane_state->hw.color_range == DRM_COLOR_YCBCR_FULL_RANGE)
plane_color_ctl |= PLANE_COLOR_YUV_RANGE_CORRECTION_DISABLE;
}

return plane_color_ctl;
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65 changes: 10 additions & 55 deletions drivers/gpu/drm/i915/display/intel_sprite.c
View file
Expand Up @@ -469,13 +469,19 @@ skl_program_scaler(struct intel_plane *plane,

/* Preoffset values for YUV to RGB Conversion */
#define PREOFF_YUV_TO_RGB_HI 0x1800
#define PREOFF_YUV_TO_RGB_ME 0x1F00
#define PREOFF_YUV_TO_RGB_ME 0x0000
#define PREOFF_YUV_TO_RGB_LO 0x1800

#define ROFF(x) (((x) & 0xffff) << 16)
#define GOFF(x) (((x) & 0xffff) << 0)
#define BOFF(x) (((x) & 0xffff) << 16)

/*
* Programs the input color space conversion stage for ICL HDR planes.
* Note that it is assumed that this stage always happens after YUV
* range correction. Thus, the input to this stage is assumed to be
* in full-range YCbCr.
*/
static void
icl_program_input_csc(struct intel_plane *plane,
const struct intel_crtc_state *crtc_state,
Expand Down Expand Up @@ -523,52 +529,7 @@ icl_program_input_csc(struct intel_plane *plane,
0x0, 0x7800, 0x7F10,
},
};

/* Matrix for Limited Range to Full Range Conversion */
static const u16 input_csc_matrix_lr[][9] = {
/*
* BT.601 Limted range YCbCr -> full range RGB
* The matrix required is :
* [1.164384, 0.000, 1.596027,
* 1.164384, -0.39175, -0.812813,
* 1.164384, 2.017232, 0.0000]
*/
[DRM_COLOR_YCBCR_BT601] = {
0x7CC8, 0x7950, 0x0,
0x8D00, 0x7950, 0x9C88,
0x0, 0x7950, 0x6810,
},
/*
* BT.709 Limited range YCbCr -> full range RGB
* The matrix required is :
* [1.164384, 0.000, 1.792741,
* 1.164384, -0.213249, -0.532909,
* 1.164384, 2.112402, 0.0000]
*/
[DRM_COLOR_YCBCR_BT709] = {
0x7E58, 0x7950, 0x0,
0x8888, 0x7950, 0xADA8,
0x0, 0x7950, 0x6870,
},
/*
* BT.2020 Limited range YCbCr -> full range RGB
* The matrix required is :
* [1.164, 0.000, 1.678,
* 1.164, -0.1873, -0.6504,
* 1.164, 2.1417, 0.0000]
*/
[DRM_COLOR_YCBCR_BT2020] = {
0x7D70, 0x7950, 0x0,
0x8A68, 0x7950, 0xAC00,
0x0, 0x7950, 0x6890,
},
};
const u16 *csc;

if (plane_state->hw.color_range == DRM_COLOR_YCBCR_FULL_RANGE)
csc = input_csc_matrix[plane_state->hw.color_encoding];
else
csc = input_csc_matrix_lr[plane_state->hw.color_encoding];
const u16 *csc = input_csc_matrix[plane_state->hw.color_encoding];

intel_de_write_fw(dev_priv, PLANE_INPUT_CSC_COEFF(pipe, plane_id, 0),
ROFF(csc[0]) | GOFF(csc[1]));
Expand All @@ -585,14 +546,8 @@ icl_program_input_csc(struct intel_plane *plane,

intel_de_write_fw(dev_priv, PLANE_INPUT_CSC_PREOFF(pipe, plane_id, 0),
PREOFF_YUV_TO_RGB_HI);
if (plane_state->hw.color_range == DRM_COLOR_YCBCR_FULL_RANGE)
intel_de_write_fw(dev_priv,
PLANE_INPUT_CSC_PREOFF(pipe, plane_id, 1),
0);
else
intel_de_write_fw(dev_priv,
PLANE_INPUT_CSC_PREOFF(pipe, plane_id, 1),
PREOFF_YUV_TO_RGB_ME);
intel_de_write_fw(dev_priv, PLANE_INPUT_CSC_PREOFF(pipe, plane_id, 1),
PREOFF_YUV_TO_RGB_ME);
intel_de_write_fw(dev_priv, PLANE_INPUT_CSC_PREOFF(pipe, plane_id, 2),
PREOFF_YUV_TO_RGB_LO);
intel_de_write_fw(dev_priv,
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