drm/i915: Allow "max bpc" property to limit pipe_bpp

Use the newly added "max bpc" connector property to limit pipe bpp.

V3: Use drm_connector_state to access the "max bpc" property
V4: Initialize the drm property, add suuport to DP(Ville)
V5: Use the property in the connector and fix CI failure(Ville)
V6: Use the core function to attach max_bpc property, remove the redundant
    clamping of pipe bpp based on connector info
V7: Fix Checkpatch warnings
V9: Cleanup connected_sink_max_bpp and fix initial value in DP(Ville)
V12: Fix debug message(Ville)
V13: Remove the redundant check and simplify the check logic(Stan)
V14: Fix the check in connected_sink_max_bpp(Stan)
v15 (From Manasi): Add missing break (Stan)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Kishore Kadiyala <kishore.kadiyala@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023014400.16055-1-manasi.d.navare@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -10928,30 +10928,38 @@ static void intel_modeset_update_connector_atomic_state(struct drm_device *dev)
 	drm_connector_list_iter_end(&conn_iter);
 }
 
-static void
-connected_sink_compute_bpp(struct intel_connector *connector,
-			   struct intel_crtc_state *pipe_config)
+static int
+connected_sink_max_bpp(const struct drm_connector_state *conn_state,
+		       struct intel_crtc_state *pipe_config)
 {
-	const struct drm_display_info *info = &connector->base.display_info;
-	int bpp = pipe_config->pipe_bpp;
-
-	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] checking for sink bpp constrains\n",
-		      connector->base.base.id,
-		      connector->base.name);
+	int bpp;
+	struct drm_display_info *info = &conn_state->connector->display_info;
 
-	/* Don't use an invalid EDID bpc value */
-	if (info->bpc != 0 && info->bpc * 3 < bpp) {
-		DRM_DEBUG_KMS("clamping display bpp (was %d) to EDID reported max of %d\n",
-			      bpp, info->bpc * 3);
-		pipe_config->pipe_bpp = info->bpc * 3;
+	switch (conn_state->max_bpc) {
+	case 6 ... 7:
+		bpp = 6 * 3;
+		break;
+	case 8 ... 9:
+		bpp = 8 * 3;
+		break;
+	case 10 ... 11:
+		bpp = 10 * 3;
+		break;
+	case 12:
+		bpp = 12 * 3;
+		break;
+	default:
+		return -EINVAL;
 	}
 
-	/* Clamp bpp to 8 on screens without EDID 1.4 */
-	if (info->bpc == 0 && bpp > 24) {
-		DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit of 24\n",
-			      bpp);
-		pipe_config->pipe_bpp = 24;
+	if (bpp < pipe_config->pipe_bpp) {
+		DRM_DEBUG_KMS("Limiting display bpp to %d instead of Edid bpp "
+			      "%d, requested bpp %d, max platform bpp %d\n", bpp,
+			      3 * info->bpc, 3 * conn_state->max_requested_bpc,
+			      pipe_config->pipe_bpp);
+		pipe_config->pipe_bpp = bpp;
 	}
+	return 0;
 }
 
 static int
@@ -10982,8 +10990,8 @@ compute_baseline_pipe_bpp(struct intel_crtc *crtc,
 		if (connector_state->crtc != &crtc->base)
 			continue;
 
-		connected_sink_compute_bpp(to_intel_connector(connector),
-					   pipe_config);
+		if (connected_sink_max_bpp(connector_state, pipe_config) < 0)
+			return -EINVAL;
 	}
 
 	return bpp;

drivers/gpu/drm/i915/intel_dp.c

@@ -5859,6 +5859,10 @@ intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connect
 		intel_attach_force_audio_property(connector);
 
 	intel_attach_broadcast_rgb_property(connector);
+	if (HAS_GMCH_DISPLAY(dev_priv))
+		drm_connector_attach_max_bpc_property(connector, 6, 10);
+	else if (INTEL_GEN(dev_priv) >= 5)
+		drm_connector_attach_max_bpc_property(connector, 6, 12);
 
 	if (intel_dp_is_edp(intel_dp)) {
 		u32 allowed_scalers;

drivers/gpu/drm/i915/intel_hdmi.c

@@ -2129,11 +2129,16 @@ static const struct drm_encoder_funcs intel_hdmi_enc_funcs = {
 static void
 intel_hdmi_add_properties(struct intel_hdmi *intel_hdmi, struct drm_connector *connector)
 {
+	struct drm_i915_private *dev_priv = to_i915(connector->dev);
+
 	intel_attach_force_audio_property(connector);
 	intel_attach_broadcast_rgb_property(connector);
 	intel_attach_aspect_ratio_property(connector);
 	drm_connector_attach_content_type_property(connector);
 	connector->state->picture_aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
+
+	if (!HAS_GMCH_DISPLAY(dev_priv))
+		drm_connector_attach_max_bpc_property(connector, 8, 12);
 }
 
 /*