drm/i915: set phase sync pointer override enable before setting phase sync pointer

We need to unlock the phase sync pointer enable bit before we can
actually enable the phase sync pointer workaround on Ironlake.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_reg.h

@@ -3005,7 +3005,8 @@
 
 #define FDI_RXA_CHICKEN         0xc200c
 #define FDI_RXB_CHICKEN         0xc2010
-#define  FDI_RX_PHASE_SYNC_POINTER_ENABLE       (1)
+#define  FDI_RX_PHASE_SYNC_POINTER_OVR	(1<<1)
+#define  FDI_RX_PHASE_SYNC_POINTER_EN	(1<<0)
 #define FDI_RX_CHICKEN(pipe) _PIPE(pipe, FDI_RXA_CHICKEN, FDI_RXB_CHICKEN)
 
 #define SOUTH_DSPCLK_GATE_D	0xc2020

drivers/gpu/drm/i915/intel_display.c

@@ -2273,7 +2273,11 @@ static void ironlake_fdi_link_train(struct drm_crtc *crtc)
 	udelay(150);
 
 	/* Ironlake workaround, enable clock pointer after FDI enable*/
-	I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_ENABLE);
+	if (HAS_PCH_IBX(dev)) {
+		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
+		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR |
+			   FDI_RX_PHASE_SYNC_POINTER_EN);
+	}
 
 	reg = FDI_RX_IIR(pipe);
 	for (tries = 0; tries < 5; tries++) {
@@ -2516,10 +2520,12 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
 	udelay(100);
 
 	/* Ironlake workaround, disable clock pointer after downing FDI */
-	if (HAS_PCH_IBX(dev))
+	if (HAS_PCH_IBX(dev)) {
+		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
 		I915_WRITE(FDI_RX_CHICKEN(pipe),
 			   I915_READ(FDI_RX_CHICKEN(pipe) &
-				     ~FDI_RX_PHASE_SYNC_POINTER_ENABLE));
+				     ~FDI_RX_PHASE_SYNC_POINTER_EN));
+	}
 
 	/* still set train pattern 1 */
 	reg = FDI_TX_CTL(pipe);