[Intel-gfx] [PATCH 2/2] drm/i915/dp: read sink MSO configuration for eDP 1.4+

[Jani Nikula <jani.nikula@intel.com>]

Read and debug log the eDP sink MSO configuration. Do not actually do
anything with the information yet besides logging, as there's no source
MSO implementation.

Cc: Nischal Varide <nischal.varide@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 29 +++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 4a2945324e7c..70d3163a9f58 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4175,6 +4175,33 @@ static void intel_dp_get_dsc_sink_cap(struct intel_dp *intel_dp)
 	}
 }
 
+static void intel_dp_mso_init(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 mso;
+
+	if (intel_dp->edp_dpcd[0] < DP_EDP_14)
+		return;
+
+	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_MSO_LINK_CAPABILITIES, &mso) != 1) {
+		drm_err(&i915->drm, "Failed to read MSO cap\n");
+		return;
+	}
+
+	/* Valid configurations are SST or MSO 2x1, 2x2, 4x1 */
+	mso &= DP_EDP_MSO_NUMBER_OF_LINKS_MASK;
+	if (mso % 2 || mso > drm_dp_max_lane_count(intel_dp->dpcd)) {
+		drm_err(&i915->drm, "Invalid MSO link count cap %u\n", mso);
+		mso = 0;
+	}
+
+	if (mso) {
+		drm_dbg_kms(&i915->drm, "Sink MSO %ux%u configuration\n",
+			    mso, drm_dp_max_lane_count(intel_dp->dpcd) / mso);
+		drm_err(&i915->drm, "Sink uses MSO, no source support\n");
+	}
+}
+
 static bool
 intel_edp_init_dpcd(struct intel_dp *intel_dp)
 {
@@ -4258,6 +4285,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 	 */
 	intel_edp_init_source_oui(intel_dp, true);
 
+	intel_dp_mso_init(intel_dp);
+
 	return true;
 }
 
-- 
2.20.1

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