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);