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Subject[PATCH 5.10 082/120] drm/i915/display: Prevent double YUV range correction on HDR planes
Date
From: Andres Calderon Jaramillo <andrescj@chromium.org>

commit 00f9a08fbc3c703b71842a5425c1eb82053c8a70 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 fed387572040e84ead53852a7820e30a30e515d0)
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>
---
drivers/gpu/drm/i915/display/intel_display.c | 2
drivers/gpu/drm/i915/display/intel_sprite.c | 65 ++++-----------------------
2 files changed, 12 insertions(+), 55 deletions(-)

--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -4880,6 +4880,8 @@ u32 glk_plane_color_ctl(const struct int
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;
--- a/drivers/gpu/drm/i915/display/intel_sprite.c
+++ b/drivers/gpu/drm/i915/display/intel_sprite.c
@@ -469,13 +469,19 @@ skl_program_scaler(struct intel_plane *p

/* 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,
@@ -523,52 +529,7 @@ icl_program_input_csc(struct intel_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]));
@@ -585,14 +546,8 @@ icl_program_input_csc(struct intel_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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