drm/i915/ringbuffer: set FORCE_WAKE bit before reading ring register
Before reading ring register, set FORCE_WAKE bit to prevent GT core
power down to low power state, otherwise we may read stale values.
Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
[ickle: added a udelay which seemed to do the trick on my SNB]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 61fe261..1eca8e7 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3077,4 +3077,5 @@
#define EDP_LINK_TRAIN_800MV_0DB_SNB_B (0x38<<22)
#define EDP_LINK_TRAIN_VOL_EMP_MASK_SNB (0x3f<<22)
+#define FORCEWAKE 0xA18C
#endif /* _I915_REG_H_ */