drm/i915: Set two chicken bits implicated in missed IRQs on Ivybridge.

They don't fix our problems alone, but we're told to set them.
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/i915_reg.h

@@ -3020,6 +3020,10 @@
 #define   ILK_DPFC_DIS1		(1<<8)
 #define   ILK_DPFC_DIS2		(1<<9)
 
+#define IVB_CHICKEN3	0x4200c
+# define CHICKEN3_DGMG_REQ_OUT_FIX_DISABLE	(1 << 5)
+# define CHICKEN3_DGMG_DONE_FIX_DISABLE		(1 << 2)
+
 #define DISP_ARB_CTL	0x45000
 #define  DISP_TILE_SURFACE_SWIZZLING	(1<<13)
 #define  DISP_FBC_WM_DIS		(1<<15)

drivers/gpu/drm/i915/intel_display.c

@@ -8450,6 +8450,10 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 
 	I915_WRITE(ILK_DSPCLK_GATE, IVB_VRHUNIT_CLK_GATE);
 
+	I915_WRITE(IVB_CHICKEN3,
+		   CHICKEN3_DGMG_REQ_OUT_FIX_DISABLE |
+		   CHICKEN3_DGMG_DONE_FIX_DISABLE);
+
 	for_each_pipe(pipe) {
 		I915_WRITE(DSPCNTR(pipe),
 			   I915_READ(DSPCNTR(pipe)) |