drm/i915: Set up the documented clock gating on Sandybridge and Ironlake.

Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 2720bc2..cbbf59f 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2176,6 +2176,14 @@
 #define DISPLAY_PORT_PLL_BIOS_1         0x46010
 #define DISPLAY_PORT_PLL_BIOS_2         0x46014
 
+#define PCH_DSPCLK_GATE_D	0x42020
+# define DPFDUNIT_CLOCK_GATE_DISABLE		(1 << 7)
+# define DPARBUNIT_CLOCK_GATE_DISABLE		(1 << 5)
+
+#define PCH_3DCGDIS0		0x46020
+# define MARIUNIT_CLOCK_GATE_DISABLE		(1 << 18)
+# define SVSMUNIT_CLOCK_GATE_DISABLE		(1 << 1)
+
 #define FDI_PLL_FREQ_CTL        0x46030
 #define  FDI_PLL_FREQ_CHANGE_REQUEST    (1<<24)
 #define  FDI_PLL_FREQ_LOCK_LIMIT_MASK   0xfff00