drm/i915: move fdi lane configuration checks ahead

This nicely allows us to drop some hacks which have only been used
to work around modeset failures due to lack of fdi lanes.

v2: Implement proper checking for Haswell platforms - the fdi link to
the LPT PCH has only 2 lanes. Note that we already filter out
impossible modes in intel_crt_mode_valid. Unfortunately LPT does not
support 6bpc on the fdi rx, so we can't pull clever tricks to squeeze
in a few more modes.

v2: Rebased on top of Ben Widawsky's num_pipes reorg.

v3: Rebase on top of Ville's pipe debug output ocd rampage.

v4: Fixup rebase fail spotted by Ville.

v5: Fixup rebase fail spotted by Imre Deak. I suck.

Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3974,9 +3974,68 @@ bool intel_connector_get_hw_state(struct intel_connector *connector)
 	return encoder->get_hw_state(encoder, &pipe);
 }
 
-static void ironlake_fdi_compute_config(struct drm_device *dev,
+static bool ironlake_check_fdi_lanes(struct drm_device *dev, enum pipe pipe,
+				     struct intel_crtc_config *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) {
+		DRM_DEBUG_KMS("invalid fdi lane config on pipe %c: %i lanes\n",
+			      pipe_name(pipe), pipe_config->fdi_lanes);
+		return false;
+	}
+
+	if (IS_HASWELL(dev)) {
+		if (pipe_config->fdi_lanes > 2) {
+			DRM_DEBUG_KMS("only 2 lanes on haswell, required: %i lanes\n",
+				      pipe_config->fdi_lanes);
+			return false;
+		} else {
+			return true;
+		}
+	}
+
+	if (INTEL_INFO(dev)->num_pipes == 2)
+		return true;
+
+	/* Ivybridge 3 pipe is really complicated */
+	switch (pipe) {
+	case PIPE_A:
+		return true;
+	case PIPE_B:
+		if (dev_priv->pipe_to_crtc_mapping[PIPE_C]->enabled &&
+		    pipe_config->fdi_lanes > 2) {
+			DRM_DEBUG_KMS("invalid shared fdi lane config on pipe %c: %i lanes\n",
+				      pipe_name(pipe), pipe_config->fdi_lanes);
+			return false;
+		}
+		return true;
+	case PIPE_C:
+		if (!pipe_B_crtc->base.enabled ||
+		    pipe_B_crtc->config.fdi_lanes <= 2) {
+			if (pipe_config->fdi_lanes > 2) {
+				DRM_DEBUG_KMS("invalid shared fdi lane config on pipe %c: %i lanes\n",
+					      pipe_name(pipe), pipe_config->fdi_lanes);
+				return false;
+			}
+		} else {
+			DRM_DEBUG_KMS("fdi link B uses too many lanes to enable link C\n");
+			return false;
+		}
+		return true;
+	default:
+		BUG();
+	}
+}
+
+static bool ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
 					struct intel_crtc_config *pipe_config)
 {
+	struct drm_device *dev = intel_crtc->base.dev;
 	struct drm_display_mode *adjusted_mode = &pipe_config->adjusted_mode;
 	int target_clock, lane, link_bw;
 
@@ -4003,6 +4062,9 @@ static void ironlake_fdi_compute_config(struct drm_device *dev,
 		link_bw *= pipe_config->pixel_multiplier;
 	intel_link_compute_m_n(pipe_config->pipe_bpp, lane, target_clock,
 			       link_bw, &pipe_config->fdi_m_n);
+
+	return ironlake_check_fdi_lanes(intel_crtc->base.dev,
+					intel_crtc->pipe, pipe_config);
 }
 
 static bool intel_crtc_compute_config(struct drm_crtc *crtc,
@@ -4040,7 +4102,7 @@ static bool intel_crtc_compute_config(struct drm_crtc *crtc,
 	}
 
 	if (pipe_config->has_pch_encoder)
-		ironlake_fdi_compute_config(dev, pipe_config);
+		return ironlake_fdi_compute_config(to_intel_crtc(crtc), pipe_config);
 
 	return true;
 }
@@ -5424,63 +5486,6 @@ static void cpt_enable_fdi_bc_bifurcation(struct drm_device *dev)
 	POSTING_READ(SOUTH_CHICKEN1);
 }
 
-static bool ironlake_check_fdi_lanes(struct intel_crtc *intel_crtc)
-{
-	struct drm_device *dev = intel_crtc->base.dev;
-	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(intel_crtc->pipe), intel_crtc->config.fdi_lanes);
-	if (intel_crtc->config.fdi_lanes > 4) {
-		DRM_DEBUG_KMS("invalid fdi lane config on pipe %c: %i lanes\n",
-			      pipe_name(intel_crtc->pipe), intel_crtc->config.fdi_lanes);
-		/* Clamp lanes to avoid programming the hw with bogus values. */
-		intel_crtc->config.fdi_lanes = 4;
-
-		return false;
-	}
-
-	if (INTEL_INFO(dev)->num_pipes == 2)
-		return true;
-
-	switch (intel_crtc->pipe) {
-	case PIPE_A:
-		return true;
-	case PIPE_B:
-		if (dev_priv->pipe_to_crtc_mapping[PIPE_C]->enabled &&
-		    intel_crtc->config.fdi_lanes > 2) {
-			DRM_DEBUG_KMS("invalid shared fdi lane config on pipe %c: %i lanes\n",
-				      pipe_name(intel_crtc->pipe), intel_crtc->config.fdi_lanes);
-			/* Clamp lanes to avoid programming the hw with bogus values. */
-			intel_crtc->config.fdi_lanes = 2;
-
-			return false;
-		}
-
-		return true;
-	case PIPE_C:
-		if (!pipe_B_crtc->base.enabled || pipe_B_crtc->config.fdi_lanes <= 2) {
-			if (intel_crtc->config.fdi_lanes > 2) {
-				DRM_DEBUG_KMS("invalid shared fdi lane config on pipe %c: %i lanes\n",
-					      pipe_name(intel_crtc->pipe), intel_crtc->config.fdi_lanes);
-				/* Clamp lanes to avoid programming the hw with bogus values. */
-				intel_crtc->config.fdi_lanes = 2;
-
-				return false;
-			}
-		} else {
-			DRM_DEBUG_KMS("fdi link B uses too many lanes to enable link C\n");
-			return false;
-		}
-
-		return true;
-	default:
-		BUG();
-	}
-}
-
 static void ivybridge_update_fdi_bc_bifurcation(struct intel_crtc *intel_crtc)
 {
 	struct drm_device *dev = intel_crtc->base.dev;
@@ -5672,7 +5677,6 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	bool is_lvds = false;
 	struct intel_encoder *encoder;
 	int ret;
-	bool fdi_config_ok;
 
 	for_each_encoder_on_crtc(dev, crtc, encoder) {
 		switch (encoder->type) {
@@ -5765,14 +5769,11 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 
 	intel_set_pipe_timings(intel_crtc, mode, adjusted_mode);
 
-	/* Note, this also computes intel_crtc->fdi_lanes which is used below in
-	 * ironlake_check_fdi_lanes. */
 	if (intel_crtc->config.has_pch_encoder) {
 		intel_cpu_transcoder_set_m_n(intel_crtc,
 					     &intel_crtc->config.fdi_m_n);
 	}
 
-	fdi_config_ok = ironlake_check_fdi_lanes(intel_crtc);
 	if (IS_IVYBRIDGE(dev))
 		ivybridge_update_fdi_bc_bifurcation(intel_crtc);
 
@@ -5788,7 +5789,7 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 
 	intel_update_linetime_watermarks(dev, pipe, adjusted_mode);
 
-	return fdi_config_ok ? ret : -EINVAL;
+	return ret;
 }
 
 static bool ironlake_get_pipe_config(struct intel_crtc *crtc,