drm/i915: prepare csc unit for YCBCR420 output

To support ycbcr output, we need a pipe CSC block to do
RGB->YCBCR conversion.

Current Intel platforms have only one pipe CSC unit, so
we can either do color correction using it, or we can perform
RGB->YCBCR conversion.

This function adds a csc handler, which uses recommended bspec
values to perform RGB->YCBCR conversion (target color space BT709)

V2: Rebase
V3: Rebase
V4: Rebase
V5: Addressed review comments from Ander
    - Remove extra line added in the patch
    - Add the spec details in the commit message
    - Combine two if(cond) while calling intel_crtc_compute_config
V6: Handle YCBCR420 outputs only (Ville)
V7: Addressed review comments from Ville:
    - Add description about target colorspace
    - Remove the comments from CSC function
    - DRM_DEBUG->DEBUG_KMS for atomic failure due to CSC unit busy
    - Remove unnecessary debug message about YCBCR420 possibe
V8: Addressed review comments from Ville:
    - Remove extra comment, not required.
    - Do not add extra variable for CTM, reuse pipe_config
    Added r-b from Ville
V9: Remove extra whitespace (Imre)
V10: Added r-b from Imre

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Cc: Imre Deak <imre.deak@intel.com>

Reviewed-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1500650709-14447-5-git-send-email-shashank.sharma@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_color.c

@@ -41,6 +41,22 @@
 
 #define LEGACY_LUT_LENGTH		(sizeof(struct drm_color_lut) * 256)
 
+/* Post offset values for RGB->YCBCR conversion */
+#define POSTOFF_RGB_TO_YUV_HI 0x800
+#define POSTOFF_RGB_TO_YUV_ME 0x100
+#define POSTOFF_RGB_TO_YUV_LO 0x800
+
+/*
+ * These values are direct register values specified in the Bspec,
+ * for RGB->YUV conversion matrix (colorspace BT709)
+ */
+#define CSC_RGB_TO_YUV_RU_GU 0x2ba809d8
+#define CSC_RGB_TO_YUV_BU 0x37e80000
+#define CSC_RGB_TO_YUV_RY_GY 0x1e089cc0
+#define CSC_RGB_TO_YUV_BY 0xb5280000
+#define CSC_RGB_TO_YUV_RV_GV 0xbce89ad8
+#define CSC_RGB_TO_YUV_BV 0x1e080000
+
 /*
  * Extract the CSC coefficient from a CTM coefficient (in U32.32 fixed point
  * format). This macro takes the coefficient we want transformed and the
@@ -91,6 +107,30 @@ static void ctm_mult_by_limited(uint64_t *result, int64_t *input)
 	}
 }
 
+void i9xx_load_ycbcr_conversion_matrix(struct intel_crtc *intel_crtc)
+{
+	int pipe = intel_crtc->pipe;
+	struct drm_i915_private *dev_priv = to_i915(intel_crtc->base.dev);
+
+	I915_WRITE(PIPE_CSC_PREOFF_HI(pipe), 0);
+	I915_WRITE(PIPE_CSC_PREOFF_ME(pipe), 0);
+	I915_WRITE(PIPE_CSC_PREOFF_LO(pipe), 0);
+
+	I915_WRITE(PIPE_CSC_COEFF_RU_GU(pipe), CSC_RGB_TO_YUV_RU_GU);
+	I915_WRITE(PIPE_CSC_COEFF_BU(pipe), CSC_RGB_TO_YUV_BU);
+
+	I915_WRITE(PIPE_CSC_COEFF_RY_GY(pipe), CSC_RGB_TO_YUV_RY_GY);
+	I915_WRITE(PIPE_CSC_COEFF_BY(pipe), CSC_RGB_TO_YUV_BY);
+
+	I915_WRITE(PIPE_CSC_COEFF_RV_GV(pipe), CSC_RGB_TO_YUV_RV_GV);
+	I915_WRITE(PIPE_CSC_COEFF_BV(pipe), CSC_RGB_TO_YUV_BV);
+
+	I915_WRITE(PIPE_CSC_POSTOFF_HI(pipe), POSTOFF_RGB_TO_YUV_HI);
+	I915_WRITE(PIPE_CSC_POSTOFF_ME(pipe), POSTOFF_RGB_TO_YUV_ME);
+	I915_WRITE(PIPE_CSC_POSTOFF_LO(pipe), POSTOFF_RGB_TO_YUV_LO);
+	I915_WRITE(PIPE_CSC_MODE(pipe), 0);
+}
+
 /* Set up the pipe CSC unit. */
 static void i9xx_load_csc_matrix(struct drm_crtc_state *crtc_state)
 {
@@ -101,7 +141,10 @@ static void i9xx_load_csc_matrix(struct drm_crtc_state *crtc_state)
 	uint16_t coeffs[9] = { 0, };
 	struct intel_crtc_state *intel_crtc_state = to_intel_crtc_state(crtc_state);
 
-	if (crtc_state->ctm) {
+	if (intel_crtc_state->ycbcr420) {
+		i9xx_load_ycbcr_conversion_matrix(intel_crtc);
+		return;
+	} else if (crtc_state->ctm) {
 		struct drm_color_ctm *ctm =
 			(struct drm_color_ctm *)crtc_state->ctm->data;
 		uint64_t input[9] = { 0, };

drivers/gpu/drm/i915/intel_display.c

@@ -6140,6 +6140,16 @@ static int intel_crtc_compute_config(struct intel_crtc *crtc,
 		return -EINVAL;
 	}
 
+	if (pipe_config->ycbcr420 && pipe_config->base.ctm) {
+		/*
+		 * There is only one pipe CSC unit per pipe, and we need that
+		 * for output conversion from RGB->YCBCR. So if CTM is already
+		 * applied we can't support YCBCR420 output.
+		 */
+		DRM_DEBUG_KMS("YCBCR420 and CTM together are not possible\n");
+		return -EINVAL;
+	}
+
 	/*
 	 * Pipe horizontal size must be even in:
 	 * - DVO ganged mode