drm/i915: Verify Ironlake eDP presence on DP_A using the capability fuse

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_reg.h

@@ -2591,6 +2591,13 @@
 #define ILK_DISPLAY_CHICKEN2	0x42004
 #define  ILK_DPARB_GATE	(1<<22)
 #define  ILK_VSDPFD_FULL	(1<<21)
+#define ILK_DISPLAY_CHICKEN_FUSES	0x42014
+#define  ILK_INTERNAL_GRAPHICS_DISABLE	(1<<31)
+#define  ILK_INTERNAL_DISPLAY_DISABLE	(1<<30)
+#define  ILK_DISPLAY_DEBUG_DISABLE	(1<<29)
+#define  ILK_HDCP_DISABLE		(1<<25)
+#define  ILK_eDP_A_DISABLE		(1<<24)
+#define  ILK_DESKTOP			(1<<23)
 #define ILK_DSPCLK_GATE		0x42020
 #define  ILK_DPARB_CLK_GATE	(1<<5)
 /* According to spec this bit 7/8/9 of 0x42020 should be set to enable FBC */

drivers/gpu/drm/i915/intel_display.c

@@ -5379,6 +5379,23 @@ static int intel_encoder_clones(struct drm_device *dev, int type_mask)
 	return index_mask;
 }
 
+static bool has_edp_a(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (!IS_MOBILE(dev))
+		return false;
+
+	if ((I915_READ(DP_A) & DP_DETECTED) == 0)
+		return false;
+
+	if (IS_GEN5(dev) &&
+	    (I915_READ(ILK_DISPLAY_CHICKEN_FUSES) & ILK_eDP_A_DISABLE))
+		return false;
+
+	return true;
+}
+
 static void intel_setup_outputs(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -5396,7 +5413,7 @@ static void intel_setup_outputs(struct drm_device *dev)
 	if (HAS_PCH_SPLIT(dev)) {
 		dpd_is_edp = intel_dpd_is_edp(dev);
 
-		if (IS_MOBILE(dev) && (I915_READ(DP_A) & DP_DETECTED))
+		if (has_edp_a(dev))
 			intel_dp_init(dev, DP_A);
 
 		if (dpd_is_edp && (I915_READ(PCH_DP_D) & DP_DETECTED))