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>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5e839c7..48d8fd6 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2212,9 +2212,10 @@
 	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);