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drm/i915: possibly invalidate TLB before context switch

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From http://intellinuxgraphics.org/documentation/SNB/IHD_OS_Vol1_Part3.pdf

[DevSNB] If Flush TLB invalidation Mode is enabled it's the driver's
responsibility to invalidate the TLBs at least once after the previous
context switch after any GTT mappings changed (including new GTT
entries).  This can be done by a pipelined PIPE_CONTROL with TLB inv bit
set immediately before MI_SET_CONTEXT.

On GEN7 the invalidation mode is explicitly set, but this appears to be
lacking for GEN6. Since I don't know the history on this, I've decided
to dynamically read the value at ring init time, and use that value
throughout.

v2: better comment (daniel)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
This commit is contained in:
Ben Widawsky
2012-06-04 14:42:50 -07:00
committed by Daniel Vetter
parent cc0f639822
commit 12b0286f49
3 changed files with 22 additions and 0 deletions
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7
drivers/gpu/drm/i915/intel_ringbuffer.c
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@@ -423,6 +423,13 @@ static int init_render_ring(struct intel_ring_buffer *ring)
*/
I915_WRITE(CACHE_MODE_0,
_MASKED_BIT_DISABLE(CM0_STC_EVICT_DISABLE_LRA_SNB));
/* This is not explicitly set for GEN6, so read the register.
* see intel_ring_mi_set_context() for why we care.
* TODO: consider explicitly setting the bit for GEN5
*/
ring->itlb_before_ctx_switch =
!!(I915_READ(GFX_MODE) & GFX_TLB_INVALIDATE_ALWAYS);
}
if (INTEL_INFO(dev)->gen >= 6)