drm/i915: disable LVDS clock gating on CPT v2

Needed to prevent display corruption in high res panels.

v2: use correct unit names (Rodrigo)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by:  Ulrich Drepper <drepper@gmail.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -4279,7 +4279,9 @@
 #define FDI_RX_CHICKEN(pipe) _PIPE(pipe, _FDI_RXA_CHICKEN, _FDI_RXB_CHICKEN)
 
 #define SOUTH_DSPCLK_GATE_D	0xc2020
+#define  PCH_DPLUNIT_CLOCK_GATE_DISABLE (1<<30)
 #define  PCH_DPLSUNIT_CLOCK_GATE_DISABLE (1<<29)
+#define  PCH_CPUNIT_CLOCK_GATE_DISABLE (1<<14)
 #define  PCH_LP_PARTITION_LEVEL_DISABLE  (1<<12)
 
 /* CPU: FDI_TX */

drivers/gpu/drm/i915/intel_pm.c

@@ -4759,7 +4759,9 @@ static void cpt_init_clock_gating(struct drm_device *dev)
 	 * gating for the panel power sequencer or it will fail to
 	 * start up when no ports are active.
 	 */
-	I915_WRITE(SOUTH_DSPCLK_GATE_D, PCH_DPLSUNIT_CLOCK_GATE_DISABLE);
+	I915_WRITE(SOUTH_DSPCLK_GATE_D, PCH_DPLSUNIT_CLOCK_GATE_DISABLE |
+		   PCH_DPLUNIT_CLOCK_GATE_DISABLE |
+		   PCH_CPUNIT_CLOCK_GATE_DISABLE);
 	I915_WRITE(SOUTH_CHICKEN2, I915_READ(SOUTH_CHICKEN2) |
 		   DPLS_EDP_PPS_FIX_DIS);
 	/* The below fixes the weird display corruption, a few pixels shifted