drm/i915: add Ironlake clock gating workaround for FDI link training

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

@@ -2782,6 +2782,7 @@
 #define FDI_RXA_CHICKEN         0xc200c
 #define FDI_RXB_CHICKEN         0xc2010
 #define  FDI_RX_PHASE_SYNC_POINTER_ENABLE       (1)
+#define FDI_RX_CHICKEN(pipe) _PIPE(pipe, FDI_RXA_CHICKEN, FDI_RXB_CHICKEN)
 
 /* CPU: FDI_TX */
 #define FDI_TXA_CTL             0x60100

drivers/gpu/drm/i915/intel_display.c

@@ -1714,6 +1714,9 @@ static void ironlake_fdi_link_train(struct drm_crtc *crtc)
 	POSTING_READ(reg);
 	udelay(150);
 
+	/* Ironlake workaround, enable clock pointer after FDI enable*/
+	I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_ENABLE);
+
 	reg = FDI_RX_IIR(pipe);
 	for (tries = 0; tries < 5; tries++) {
 		temp = I915_READ(reg);
@@ -2192,6 +2195,11 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
 	POSTING_READ(reg);
 	udelay(100);
 
+	/* Ironlake workaround, disable clock pointer after downing FDI */
+	I915_WRITE(FDI_RX_CHICKEN(pipe),
+		   I915_READ(FDI_RX_CHICKEN(pipe) &
+			     ~FDI_RX_PHASE_SYNC_POINTER_ENABLE));
+
 	/* still set train pattern 1 */
 	reg = FDI_TX_CTL(pipe);
 	temp = I915_READ(reg);