drm/i915: implement WaDisableRenderCachePipelinedFlush

Comment says for eaglelake/cantiga, but it's listed in the ilk table,
too. So apply it to both.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -670,6 +670,7 @@
 #define   MI_ARB_DISPLAY_PRIORITY_B_A		(1 << 0)	/* display B > display A */
 
 #define CACHE_MODE_0	0x02120 /* 915+ only */
+#define   CM0_PIPELINED_RENDER_FLUSH_DISABLE (1<<8)
 #define   CM0_IZ_OPT_DISABLE      (1<<6)
 #define   CM0_ZR_OPT_DISABLE      (1<<5)
 #define	  CM0_STC_EVICT_DISABLE_LRA_SNB	(1<<5)

drivers/gpu/drm/i915/intel_pm.c

@@ -3382,6 +3382,10 @@ static void ironlake_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(_3D_CHICKEN2,
 		   _3D_CHICKEN2_WM_READ_PIPELINED << 16 |
 		   _3D_CHICKEN2_WM_READ_PIPELINED);
+
+	/* WaDisableRenderCachePipelinedFlush */
+	I915_WRITE(CACHE_MODE_0,
+		   _MASKED_BIT_ENABLE(CM0_PIPELINED_RENDER_FLUSH_DISABLE));
 }
 
 static void gen6_init_clock_gating(struct drm_device *dev)
@@ -3716,6 +3720,10 @@ static void g4x_init_clock_gating(struct drm_device *dev)
 	if (IS_GM45(dev))
 		dspclk_gate |= DSSUNIT_CLOCK_GATE_DISABLE;
 	I915_WRITE(DSPCLK_GATE_D, dspclk_gate);
+
+	/* WaDisableRenderCachePipelinedFlush */
+	I915_WRITE(CACHE_MODE_0,
+		   _MASKED_BIT_ENABLE(CM0_PIPELINED_RENDER_FLUSH_DISABLE));
 }
 
 static void crestline_init_clock_gating(struct drm_device *dev)