drm/i915; Don't apply Ironlake FDI clock workaround to Sandybridge

Signed-off-by: Zhenyu Wang <zhenyu.z.wang@intel.com>
Cc: stable@kernel.org
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -1321,6 +1321,7 @@ static inline void i915_write(struct drm_i915_private *dev_priv, u32 reg,
 
 #define INTEL_PCH_TYPE(dev) (((struct drm_i915_private *)(dev)->dev_private)->pch_type)
 #define HAS_PCH_CPT(dev) (INTEL_PCH_TYPE(dev) == PCH_CPT)
+#define HAS_PCH_IBX(dev) (INTEL_PCH_TYPE(dev) == PCH_IBX)
 
 #define PRIMARY_RINGBUFFER_SIZE         (128*1024)
 

drivers/gpu/drm/i915/intel_display.c

@@ -2212,9 +2212,10 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
 	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));
+	if (HAS_PCH_IBX(dev))
+		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);