[Intel-gfx] [RFC 5/6] drm/i915/dp: Add a support of YCBCR 4:2:0 to DP MSA

[Gwan-gyeong Mun]

When YCBCR 4:2:0 outputs is used for DP, we should program YCBCR 4:2:0 to
MSA and VSC SDP.

As per DP 1.4a spec section 2.2.4.3 [MSA Field for Indication of Color
Encoding Format and Content Color Gamut] while sending YCBCR 420 signals
we should program MSA MISC1 fields which indicate VSC SDP for the Pixel
Encoding/Colorimetry Format.

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h  | 1 +
 drivers/gpu/drm/i915/intel_ddi.c | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a64deeb4e517..1045ca41b188 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -9425,6 +9425,7 @@ enum skl_power_gate {
 #define  TRANS_MSA_12_BPC		(3 << 5)
 #define  TRANS_MSA_16_BPC		(4 << 5)
 #define  TRANS_MSA_CEA_RANGE		(1 << 3)
+#define  TRANS_MSA_USE_VSC_SDP		(1 << 13)
 
 /* LCPLL Control */
 #define LCPLL_CTL			_MMIO(0x130040)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 8969f03393b8..c6aed2b06a59 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1732,6 +1732,14 @@ void intel_ddi_set_pipe_settings(const struct intel_crtc_state *crtc_state)
 	 */
 	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444)
 		temp |= TRANS_MSA_SAMPLING_444 | TRANS_MSA_CLRSP_YCBCR;
+	/*
+	 * As per DP 1.4a spec section 2.2.4.3 [MSA Field for Indication
+	 * of Color Encoding Format and Content Color Gamut] while sending
+	 * YCBCR 420 signals we should program MSA MISC1 fields which
+	 * indicate VSC SDP for the Pixel Encoding/Colorimetry Format.
+	*/
+	if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420)
+		temp |= TRANS_MSA_USE_VSC_SDP;
 	I915_WRITE(TRANS_MSA_MISC(cpu_transcoder), temp);
 }
 
-- 
2.20.1