drm/i915: Rewrite IVB FDI bifurcation conflict checks

Ignore the current state of the pipe and just check crtc_state->enable
and the number of FDI lanes required. This means we don't accidentally
mistake the FDI lanes as being available of one of the pipes just
happens to be disabled at the time of the check. Also we no longer
consider pipe C to require FDI lanes when it's driving the eDP
transcoder.

We also take the opportunity to make the code a bit nicer looking by
hiding the ugly bits in the new pipe_required_fdi_lanes() function.

Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3141,12 +3141,6 @@ static void intel_fdi_normal_train(struct drm_crtc *crtc)
 			   FDI_FE_ERRC_ENABLE);
 }
 
-static bool pipe_has_enabled_pch(struct intel_crtc *crtc)
-{
-	return crtc->base.state->enable && crtc->active &&
-		crtc->config->has_pch_encoder;
-}
-
 /* The FDI link training functions for ILK/Ibexpeak. */
 static void ironlake_fdi_link_train(struct drm_crtc *crtc)
 {
@@ -5539,13 +5533,21 @@ bool intel_connector_get_hw_state(struct intel_connector *connector)
 	return encoder->get_hw_state(encoder, &pipe);
 }
 
+static int pipe_required_fdi_lanes(struct drm_device *dev, enum pipe pipe)
+{
+	struct intel_crtc *crtc =
+		to_intel_crtc(intel_get_crtc_for_pipe(dev, pipe));
+
+	if (crtc->base.state->enable &&
+	    crtc->config->has_pch_encoder)
+		return crtc->config->fdi_lanes;
+
+	return 0;
+}
+
 static bool ironlake_check_fdi_lanes(struct drm_device *dev, enum pipe pipe,
 				     struct intel_crtc_state *pipe_config)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct intel_crtc *pipe_B_crtc =
-		to_intel_crtc(dev_priv->pipe_to_crtc_mapping[PIPE_B]);
-
 	DRM_DEBUG_KMS("checking fdi config on pipe %c, lanes %i\n",
 		      pipe_name(pipe), pipe_config->fdi_lanes);
 	if (pipe_config->fdi_lanes > 4) {
@@ -5572,8 +5574,8 @@ static bool ironlake_check_fdi_lanes(struct drm_device *dev, enum pipe pipe,
 	case PIPE_A:
 		return true;
 	case PIPE_B:
-		if (dev_priv->pipe_to_crtc_mapping[PIPE_C]->enabled &&
-		    pipe_config->fdi_lanes > 2) {
+		if (pipe_config->fdi_lanes > 2 &&
+		    pipe_required_fdi_lanes(dev, PIPE_C) > 0) {
 			DRM_DEBUG_KMS("invalid shared fdi lane config on pipe %c: %i lanes\n",
 				      pipe_name(pipe), pipe_config->fdi_lanes);
 			return false;
@@ -5585,8 +5587,7 @@ static bool ironlake_check_fdi_lanes(struct drm_device *dev, enum pipe pipe,
 				      pipe_name(pipe), pipe_config->fdi_lanes);
 			return false;
 		}
-		if (pipe_has_enabled_pch(pipe_B_crtc) &&
-		    pipe_B_crtc->config->fdi_lanes > 2) {
+		if (pipe_required_fdi_lanes(dev, PIPE_B) > 2) {
 			DRM_DEBUG_KMS("fdi link B uses too many lanes to enable link C\n");
 			return false;
 		}