[PATCH v5 15/17] drm/i915: prepare csc unit for YCBCR HDMI output

[Shashank Sharma]

To support ycbcr HDMI output, we need a pipe CSC block to
do the RGB->YCBCR conversion, as the blender output is in RGB.

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

Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Ander Conselvan de Oliveira <conselvan2 at gmail.com>

Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
---
 drivers/gpu/drm/i915/intel_color.c   | 47 +++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_display.c | 30 +++++++++++++++++++++++
 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_color.c b/drivers/gpu/drm/i915/intel_color.c
index 306c6b0..12d5f21 100644
--- a/drivers/gpu/drm/i915/intel_color.c
+++ b/drivers/gpu/drm/i915/intel_color.c
@@ -41,6 +41,19 @@
 
 #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
+
+/* Direct spec values for RGB->YUV conversion matrix */
+#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 +104,35 @@ 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);
+
+	/* We don't use high values for conversion */
+	I915_WRITE(PIPE_CSC_PREOFF_HI(pipe), 0);
+	I915_WRITE(PIPE_CSC_PREOFF_ME(pipe), 0);
+	I915_WRITE(PIPE_CSC_PREOFF_LO(pipe), 0);
+
+	/* Program direct spec values for RGB to YCBCR conversion matrix */
+	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);
+
+	/* Spec postoffset values */
+	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);
+
+	/* CSC mode before gamma */
+	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 +143,10 @@ 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->hdmi_output > DRM_HDMI_OUTPUT_DEFAULT_RGB) {
+		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, };
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3f87052..14110bd 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6260,6 +6260,29 @@ static void intel_crtc_compute_pixel_rate(struct intel_crtc_state *crtc_state)
 			ilk_pipe_pixel_rate(crtc_state);
 }
 
+static int intel_crtc_ycbcr_config(struct intel_crtc_state *state)
+{
+	struct drm_crtc_state *drm_state = &state->base;
+	struct drm_i915_private *dev_priv = to_i915(drm_state->crtc->dev);
+
+	/* YCBCR420 is supported only in HDMI 2.0 controllers */
+	if ((state->hdmi_output == DRM_HDMI_OUTPUT_YCBCR420) &&
+		!IS_GEMINILAKE(dev_priv)) {
+		DRM_ERROR("YCBCR420 output is not supported\n");
+		return -EINVAL;
+	}
+
+	/* We need CSC for output conversion from RGB->YCBCR */
+	if (drm_state->ctm) {
+		DRM_ERROR("YCBCR output and CTM is not possible together\n");
+		return -EINVAL;
+	}
+
+	DRM_DEBUG_DRIVER("Output %s can be supported\n",
+			 drm_get_hdmi_output_name(state->hdmi_output));
+	return 0;
+}
+
 static int intel_crtc_compute_config(struct intel_crtc *crtc,
 				     struct intel_crtc_state *pipe_config)
 {
@@ -6289,6 +6312,13 @@ static int intel_crtc_compute_config(struct intel_crtc *crtc,
 		return -EINVAL;
 	}
 
+	/* YCBCR output check */
+	if (pipe_config->hdmi_output > DRM_HDMI_OUTPUT_DEFAULT_RGB &&
+		intel_crtc_ycbcr_config(pipe_config)) {
+		DRM_ERROR("Can't enable YCBCR output\n");
+		return -EINVAL;
+	}
+
 	/*
 	 * Pipe horizontal size must be even in:
 	 * - DVO ganged mode
-- 
2.7.4