drm/i915: gen7: Implement an L3 caching workaround.

This adds two cache-related workarounds for Ivy Bridge which can lead to
3D ring hangs and corruptions.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41353
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44610Tested-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/gpu/drm/i915/i915_reg.h

@@ -3028,6 +3028,13 @@
 #define  DISP_TILE_SURFACE_SWIZZLING	(1<<13)
 #define  DISP_FBC_WM_DIS		(1<<15)
 
+/* GEN7 chicken */
+#define GEN7_L3CNTLREG1				0xB01C
+#define  GEN7_WA_FOR_GEN7_L3_CONTROL			0x3C4FFF8C
+
+#define GEN7_L3_CHICKEN_MODE_REGISTER		0xB030
+#define  GEN7_WA_L3_CHICKEN_MODE				0x20000000
+
 /* PCH */
 
 /* south display engine interrupt */

drivers/gpu/drm/i915/intel_display.c

@@ -8472,6 +8472,12 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 		   CHICKEN3_DGMG_REQ_OUT_FIX_DISABLE |
 		   CHICKEN3_DGMG_DONE_FIX_DISABLE);
 
+	/* WaApplyL3ControlAndL3ChickenMode requires those two on Ivy Bridge */
+	I915_WRITE(GEN7_L3CNTLREG1,
+			GEN7_WA_FOR_GEN7_L3_CONTROL);
+	I915_WRITE(GEN7_L3_CHICKEN_MODE_REGISTER,
+			GEN7_WA_L3_CHICKEN_MODE);
+
 	for_each_pipe(pipe) {
 		I915_WRITE(DSPCNTR(pipe),
 			   I915_READ(DSPCNTR(pipe)) |