[Intel-gfx] [PATCH 2/2] drm/i915: Force TLB invalidation for erratum on 830/845 BLT

[Chris Wilson]

On 830/845, the BLT unit invalidates the wrong PTE in its TLB after the
GATT is updated. A simple solution is then to always invalidate the TLB
of the BLT prior to each execbuffer.

This does appear to improve the stability slighty, but I am still seeing
spurious GPU deaths under memory pressure.

References: https://bugs.freedesktop.org/show_bug.cgi?id=26345
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 60fc132..b825c06 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -883,6 +883,13 @@ i915_gem_execbuffer_move_to_gpu(struct intel_ring_buffer *ring,
 	int ret;
 
 	memset(&cd, 0, sizeof(cd));
+
+	/* We need to invalidate the BLT's prefetched entries after
+	 * updating the GATT (as the hardware invalidates the wrong PTEs).
+	 */
+	if (IS_I830(ring->dev) || IS_845G(ring->dev))
+		cd.invalidate_domains = I915_GEM_DOMAIN_RENDER;
+
 	list_for_each_entry(obj, objects, exec_list)
 		i915_gem_object_set_to_gpu_domain(obj, ring, &cd);
 
-- 
1.7.10