drm/i915: WA: FBC Render Nuke.

WaFbcNukeOn3DBlt for IVB, HSW.

According BSPec: "Workaround: Do not enable Render Command Streamer tracking for FBC.
Instead insert a LRI to address 0x50380 with data 0x00000004 after the PIPE_CONTROL that
follows each render submission."

v2: Chris noticed that flush_domains check was missing here and also suggested to do
    LRI only when fbc is enabled. To avoid do a I915_READ on every flush lets use the
    module parameter check.

v3: Adding Wa name as Damien suggested.

v4: Ville noticed VLV doesn't support fbc at all and comment came wrong from spec.

v5: Ville noticed than on blt a Cache Clean LRI should be used instead the Nuke one.

v6: Check for flush domain on blt (by Ville).
    Check for scanout dirty (by Chris).

v7: Apply proper fbc_dirty implemented by Chris.

v8: remove unused variables.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index ff9f71a..b1fdca9 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1020,6 +1020,10 @@
 #define IPS_CTL		0x43408
 #define   IPS_ENABLE	(1 << 31)
 
+#define MSG_FBC_REND_STATE	0x50380
+#define   FBC_REND_NUKE		(1<<2)
+#define   FBC_REND_CACHE_CLEAN	(1<<1)
+
 #define _HSW_PIPE_SLICE_CHICKEN_1_A	0x420B0
 #define _HSW_PIPE_SLICE_CHICKEN_1_B	0x420B4
 #define   HSW_BYPASS_FBC_QUEUE		(1<<22)