[PATCH 2/2] i915/display/dp: SDP CRC16 for 128b132b link layer

[Arun R Murthy]

Enable SDP error detection configuration, this will set CRC16 in
128b/132b link layer.
For DISPLAY13 a hardware bit31 in register VIDEO_DIP_CTL is added to
enable/disable SDP CRC applicable for DP2.0 only, but the default value
of this bit will enable CRC16 in 128b/132b hence skipping this write.
Corrective actions on SDP corruption is yet to be defined.

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 13 +++++++++++++
 drivers/gpu/drm/i915/i915_reg.h         |  1 +
 2 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 30c55f980014..6096825a27ca 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -133,6 +133,7 @@ static void intel_dp_set_default_sink_rates(struct intel_dp *intel_dp)
 /* update sink rates from dpcd */
 static void intel_dp_set_dpcd_sink_rates(struct intel_dp *intel_dp)
 {
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	static const int dp_rates[] = {
 		162000, 270000, 540000, 810000
 	};
@@ -196,6 +197,18 @@ static void intel_dp_set_dpcd_sink_rates(struct intel_dp *intel_dp)
 			intel_dp->sink_rates[i++] = 1350000;
 		if (uhbr_rates & DP_UHBR20)
 			intel_dp->sink_rates[i++] = 2000000;
+
+		/* DP v2.0 SCR on SDP CRC16 for 128b/132b Link Layer */
+		if (HAS_DP20(i915))
+			drm_dp_dpcd_writeb(&intel_dp->aux,
+					   DP_SDP_ERROR_DETECTION,
+					   DP_SDP_CRC16_128B132B_EN);
+		/*
+		 * VIDEO_DIP_CTL register bit 31 should be set to '0' to not
+		 * disable SDP CRC. This is applicable for DISPLAY 13. Default
+		 * value of bit 31 is '0' hence discarging the write
+		 */
+		/* TODO: Corrective actions on SDP corruption yet to be defined */
 	}
 
 	intel_dp->num_sink_rates = i;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 8b2cf980f323..77e265f59978 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2674,6 +2674,7 @@
 #define   VIDEO_DIP_FREQ_2VSYNC		(2 << 16)
 #define   VIDEO_DIP_FREQ_MASK		(3 << 16)
 /* HSW and later: */
+#define	  VIDEO_DISABLE_SDP_CRC		(1 << 31)
 #define   VIDEO_DIP_ENABLE_DRM_GLK	(1 << 28)
 #define   PSR_VSC_BIT_7_SET		(1 << 27)
 #define   VSC_SELECT_MASK		(0x3 << 25)
-- 
2.25.1