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drm/i915: Document ILK+ pipe csc matrix better

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Add comments to explain the ilk pipe csc operation a bit better.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190718145053.25808-11-ville.syrjala@linux.intel.com
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
This commit is contained in:
Ville Syrjälä 2019-07-18 17:50:51 +03:00
parent ac0f01cee9
commit 174d12bcc0
1 changed files with 21 additions and 5 deletions
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26
drivers/gpu/drm/i915/display/intel_color.c
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@ -42,6 +42,21 @@
#define LEGACY_LUT_LENGTH 256
/*
* ILK+ csc matrix:
*
* |R/Cr| | c0 c1 c2 | ( |R/Cr| |preoff0| ) |postoff0|
* |G/Y | = | c3 c4 c5 | x ( |G/Y | + |preoff1| ) + |postoff1|
* |B/Cb| | c6 c7 c8 | ( |B/Cb| |preoff2| ) |postoff2|
*
* ILK/SNB don't have explicit post offsets, and instead
* CSC_MODE_YUV_TO_RGB and CSC_BLACK_SCREEN_OFFSET are used:
* CSC_MODE_YUV_TO_RGB=0 + CSC_BLACK_SCREEN_OFFSET=0 -> 1/2, 0, 1/2
* CSC_MODE_YUV_TO_RGB=0 + CSC_BLACK_SCREEN_OFFSET=1 -> 1/2, 1/16, 1/2
* CSC_MODE_YUV_TO_RGB=1 + CSC_BLACK_SCREEN_OFFSET=0 -> 0, 0, 0
* CSC_MODE_YUV_TO_RGB=1 + CSC_BLACK_SCREEN_OFFSET=1 -> 1/16, 1/16, 1/16
*/
/*
* Extract the CSC coefficient from a CTM coefficient (in U32.32 fixed point
* format). This macro takes the coefficient we want transformed and the
@ -59,37 +74,38 @@
#define ILK_CSC_POSTOFF_LIMITED_RANGE (16 * (1 << 12) / 255)
/* Nop pre/post offsets */
static const u16 ilk_csc_off_zero[3] = {};
/* Identity matrix */
static const u16 ilk_csc_coeff_identity[9] = {
ILK_CSC_COEFF_1_0, 0, 0,
0, ILK_CSC_COEFF_1_0, 0,
0, 0, ILK_CSC_COEFF_1_0,
};
/* Limited range RGB post offsets */
static const u16 ilk_csc_postoff_limited_range[3] = {
ILK_CSC_POSTOFF_LIMITED_RANGE,
ILK_CSC_POSTOFF_LIMITED_RANGE,
ILK_CSC_POSTOFF_LIMITED_RANGE,
};
/* Full range RGB -> limited range RGB matrix */
static const u16 ilk_csc_coeff_limited_range[9] = {
ILK_CSC_COEFF_LIMITED_RANGE, 0, 0,
0, ILK_CSC_COEFF_LIMITED_RANGE, 0,
0, 0, ILK_CSC_COEFF_LIMITED_RANGE,
};
/*
* These values are direct register values specified in the Bspec,
* for RGB->YUV conversion matrix (colorspace BT709)
*/
/* BT.709 full range RGB -> limited range YCbCr matrix */
static const u16 ilk_csc_coeff_rgb_to_ycbcr[9] = {
0x1e08, 0x9cc0, 0xb528,
0x2ba8, 0x09d8, 0x37e8,
0xbce8, 0x9ad8, 0x1e08,
};
/* Post offset values for RGB->YCBCR conversion */
/* Limited range YCbCr post offsets */
static const u16 ilk_csc_postoff_rgb_to_ycbcr[3] = {
0x0800, 0x0100, 0x0800,
};