drm/i915: skip FDI & PCH enabling for DP_A

eDP on the CPU doesn't need the PCH set up at all, it can in fact cause
problems.  So avoid FDI training and PCH PLL enabling in that case.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -2611,49 +2611,21 @@ static bool intel_crtc_driving_pch(struct drm_crtc *crtc)
 	return true;
 }
 
-static void ironlake_crtc_enable(struct drm_crtc *crtc)
+/*
+ * Enable PCH resources required for PCH ports:
+ *   - PCH PLLs
+ *   - FDI training & RX/TX
+ *   - update transcoder timings
+ *   - DP transcoding bits
+ *   - transcoder
+ */
+static void ironlake_pch_enable(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	int pipe = intel_crtc->pipe;
-	int plane = intel_crtc->plane;
 	u32 reg, temp;
-	bool is_pch_port;
-
-	if (intel_crtc->active)
-		return;
-
-	intel_crtc->active = true;
-	intel_update_watermarks(dev);
-
-	if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)) {
-		temp = I915_READ(PCH_LVDS);
-		if ((temp & LVDS_PORT_EN) == 0)
-			I915_WRITE(PCH_LVDS, temp | LVDS_PORT_EN);
-	}
-
-	ironlake_fdi_enable(crtc);
-
-	/* Enable panel fitting for LVDS */
-	if (dev_priv->pch_pf_size &&
-	    (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS) || HAS_eDP)) {
-		/* Force use of hard-coded filter coefficients
-		 * as some pre-programmed values are broken,
-		 * e.g. x201.
-		 */
-		I915_WRITE(pipe ? PFB_CTL_1 : PFA_CTL_1,
-			   PF_ENABLE | PF_FILTER_MED_3x3);
-		I915_WRITE(pipe ? PFB_WIN_POS : PFA_WIN_POS,
-			   dev_priv->pch_pf_pos);
-		I915_WRITE(pipe ? PFB_WIN_SZ : PFA_WIN_SZ,
-			   dev_priv->pch_pf_size);
-	}
-
-	is_pch_port = intel_crtc_driving_pch(crtc);
-
-	intel_enable_pipe(dev_priv, pipe, is_pch_port);
-	intel_enable_plane(dev_priv, plane, pipe);
 
 	/* For PCH output, training FDI link */
 	if (IS_GEN6(dev))
@@ -2722,6 +2694,57 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 	}
 
 	intel_enable_transcoder(dev_priv, pipe);
+}
+
+static void ironlake_crtc_enable(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	int pipe = intel_crtc->pipe;
+	int plane = intel_crtc->plane;
+	u32 temp;
+	bool is_pch_port;
+
+	if (intel_crtc->active)
+		return;
+
+	intel_crtc->active = true;
+	intel_update_watermarks(dev);
+
+	if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)) {
+		temp = I915_READ(PCH_LVDS);
+		if ((temp & LVDS_PORT_EN) == 0)
+			I915_WRITE(PCH_LVDS, temp | LVDS_PORT_EN);
+	}
+
+	is_pch_port = intel_crtc_driving_pch(crtc);
+
+	if (is_pch_port)
+		ironlake_fdi_enable(crtc);
+	else
+		ironlake_fdi_disable(crtc);
+
+	/* Enable panel fitting for LVDS */
+	if (dev_priv->pch_pf_size &&
+	    (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS) || HAS_eDP)) {
+		/* Force use of hard-coded filter coefficients
+		 * as some pre-programmed values are broken,
+		 * e.g. x201.
+		 */
+		I915_WRITE(pipe ? PFB_CTL_1 : PFA_CTL_1,
+			   PF_ENABLE | PF_FILTER_MED_3x3);
+		I915_WRITE(pipe ? PFB_WIN_POS : PFA_WIN_POS,
+			   dev_priv->pch_pf_pos);
+		I915_WRITE(pipe ? PFB_WIN_SZ : PFA_WIN_SZ,
+			   dev_priv->pch_pf_size);
+	}
+
+	intel_enable_pipe(dev_priv, pipe, is_pch_port);
+	intel_enable_plane(dev_priv, plane, pipe);
+
+	if (is_pch_port)
+		ironlake_pch_enable(crtc);
 
 	intel_crtc_load_lut(crtc);
 	intel_update_fbc(dev);