drm/i915: set GFX_MODE to pre-Ivybridge default value even on Ivybridge

Prior to Ivybridge, the GFX_MODE would default to 0x800, meaning that
MI_FLUSH would flush the TLBs in addition to the rest of the caches
indicated in the MI_FLUSH command.  However starting with Ivybridge, the
register defaults to 0x2800 out of reset, meaning that to invalidate the
TLB we need to use PIPE_CONTROL.  Since we're not doing that yet, go
back to the old default so things work.

v2: don't forget to actually *clear* the new bit

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/gpu/drm/i915/i915_reg.h

@@ -375,13 +375,17 @@
 # define MI_FLUSH_ENABLE				(1 << 11)
 
 #define GFX_MODE	0x02520
+#define GFX_MODE_GEN7	0x0229c
 #define   GFX_RUN_LIST_ENABLE		(1<<15)
 #define   GFX_TLB_INVALIDATE_ALWAYS	(1<<13)
 #define   GFX_SURFACE_FAULT_ENABLE	(1<<12)
 #define   GFX_REPLAY_MODE		(1<<11)
 #define   GFX_PSMI_GRANULARITY		(1<<10)
 #define   GFX_PPGTT_ENABLE		(1<<9)
 
+#define GFX_MODE_ENABLE(bit) (((bit) << 16) | (bit))
+#define GFX_MODE_DISABLE(bit) (((bit) << 16) | (0))
+
 #define SCPD0		0x0209c /* 915+ only */
 #define IER		0x020a0
 #define IIR		0x020a4

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -290,6 +290,10 @@ static int init_render_ring(struct intel_ring_buffer *ring)
 		if (IS_GEN6(dev) || IS_GEN7(dev))
 			mode |= MI_FLUSH_ENABLE << 16 | MI_FLUSH_ENABLE;
 		I915_WRITE(MI_MODE, mode);
+		if (IS_GEN7(dev))
+			I915_WRITE(GFX_MODE_GEN7,
+				   GFX_MODE_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
+				   GFX_MODE_ENABLE(GFX_REPLAY_MODE));
 	}
 
 	if (INTEL_INFO(dev)->gen >= 6) {