[PATCH] drm/i915/ddi: clarify intel_ddi_connector_get_hw_state() for DP MST

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

encoder->get_hw_state() returns false for DP MST, and currently always
interprets 128b/132b as MST. Therefore the DDI MST mode checks in
intel_ddi_connector_get_hw_state() are redundant.

Prepare for future, and handle 128b/132b SST and warn on 8b/10b MST.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index e25b712bf03b..7d37ddd9ad12 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -731,6 +731,7 @@ bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector)
 	if (!wakeref)
 		return false;
 
+	/* Note: This returns false for DP MST primary encoders. */
 	if (!encoder->get_hw_state(encoder, &pipe)) {
 		ret = false;
 		goto out;
@@ -752,12 +753,14 @@ bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector)
 	} else if (ddi_mode == TRANS_DDI_MODE_SELECT_DP_SST) {
 		ret = type == DRM_MODE_CONNECTOR_eDP ||
 			type == DRM_MODE_CONNECTOR_DisplayPort;
-	} else if (ddi_mode == TRANS_DDI_MODE_SELECT_DP_MST ||
-		   (ddi_mode == TRANS_DDI_MODE_SELECT_FDI_OR_128B132B && HAS_DP20(display))) {
+	} else if (ddi_mode == TRANS_DDI_MODE_SELECT_FDI_OR_128B132B && HAS_DP20(display)) {
 		/*
-		 * If the transcoder is in MST state then connector isn't
-		 * connected.
+		 * encoder->get_hw_state() should have bailed out on MST. This
+		 * must be SST and non-eDP.
 		 */
+		ret = type == DRM_MODE_CONNECTOR_DisplayPort;
+	} else if (drm_WARN_ON(display->drm, ddi_mode == TRANS_DDI_MODE_SELECT_DP_MST)) {
+		/* encoder->get_hw_state() should have bailed out on MST. */
 		ret = false;
 	} else {
 		ret = false;
-- 
2.39.5