drm/i915: Reworkd DFP max bpc handling

Stash the downstream facing port max bpc away during
intel_dp_set_edid(). We'll soon need the EDID in there so
we can't figure this out so easily during .compute_config() anymore.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904115354.25336-6-ville.syrjala@linux.intel.com
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1381,6 +1381,11 @@ struct intel_dp {
 	/* Displayport compliance testing */
 	struct intel_dp_compliance compliance;
 
+	/* Downstream facing port caps */
+	struct {
+		u8 max_bpc;
+	} dfp;
+
 	/* Display stream compression testing */
 	bool force_dsc_en;
 

drivers/gpu/drm/i915/display/intel_dp.c

@@ -1973,13 +1973,12 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
 {
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
-	int bpp, bpc;
+	int bpp;
 
 	bpp = pipe_config->pipe_bpp;
-	bpc = drm_dp_downstream_max_bpc(intel_dp->dpcd, intel_dp->downstream_ports);
 
-	if (bpc > 0)
-		bpp = min(bpp, 3*bpc);
+	if (intel_dp->dfp.max_bpc)
+		bpp = min(bpp, 3 * intel_dp->dfp.max_bpc);
 
 	if (intel_dp_is_edp(intel_dp)) {
 		/* Get bpp from vbt only for panels that dont have bpp in edid */
@@ -6062,12 +6061,21 @@ intel_dp_get_edid(struct intel_dp *intel_dp)
 static void
 intel_dp_set_edid(struct intel_dp *intel_dp)
 {
-	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	struct intel_connector *connector = intel_dp->attached_connector;
 	struct edid *edid;
 
 	intel_dp_unset_edid(intel_dp);
 	edid = intel_dp_get_edid(intel_dp);
-	intel_connector->detect_edid = edid;
+	connector->detect_edid = edid;
+
+	intel_dp->dfp.max_bpc =
+		drm_dp_downstream_max_bpc(intel_dp->dpcd,
+					  intel_dp->downstream_ports);
+
+	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] DFP max bpc %d\n",
+		    connector->base.base.id, connector->base.name,
+		    intel_dp->dfp.max_bpc);
 
 	if (edid && edid->input & DRM_EDID_INPUT_DIGITAL) {
 		intel_dp->has_hdmi_sink = drm_detect_hdmi_monitor(edid);
@@ -6090,6 +6098,8 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 	intel_dp->has_hdmi_sink = false;
 	intel_dp->has_audio = false;
 	intel_dp->edid_quirks = 0;
+
+	intel_dp->dfp.max_bpc = 0;
 }
 
 static int