[Intel-gfx] [PATCH 2/5] drm/i915: set w/a bit for snb pagefaults

[Daniel Vetter]

Bspec says that we need to set this: vol1c.3 "Blitter Command
Streamer", Section 1.1.2.1 "GAB_CTL_REG - GAB Unit Control Register".

We don't really rely on pagefaults, but who knows what this all
affects.

Reviewed-by: Ben Widawsky <ben at bwidawsk.net>
Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem.c |    7 ++++++-
 drivers/gpu/drm/i915/i915_reg.h |    3 +++
 2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4c65c63..5e0d7d4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3787,7 +3787,12 @@ void i915_gem_init_ppgtt(struct drm_device *dev)
 	pd_offset <<= 16;
 
 	if (INTEL_INFO(dev)->gen == 6) {
-		uint32_t ecochk = I915_READ(GAM_ECOCHK);
+		uint32_t ecochk, gab_ctl;
+
+		gab_ctl = I915_READ(GAB_CTL);
+		I915_WRITE(GAB_CTL, gab_ctl | GAB_CTL_CONT_AFTER_PAGEFAULT);
+
+		ecochk = I915_READ(GAM_ECOCHK);
 		I915_WRITE(GAM_ECOCHK, ecochk | ECOCHK_SNB_BIT |
 				       ECOCHK_PPGTT_CACHE64B);
 		I915_WRITE(GFX_MODE, GFX_MODE_ENABLE(GFX_PPGTT_ENABLE));
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 3689812..9aeee7a 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -125,6 +125,9 @@
 #define   ECOCHK_PPGTT_CACHE64B		(0x3<<3)
 #define   ECOCHK_PPGTT_CACHE4B		(0x0<<3)
 
+#define GAB_CTL				0x24000
+#define   GAB_CTL_CONT_AFTER_PAGEFAULT	(1<<8)
+
 /* VGA stuff */
 
 #define VGA_ST01_MDA 0x3ba
-- 
1.7.7.6