[Bug 91894] GPU Hangs since Kernel-4.2 upgrade

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91894

--- Comment #3 from Chris Wilson <chris at chris-wilson.co.uk> ---
libva did have a bug where they forgot to mark render targets and one of the
4.2 changes is a read-read optimisation. A hack like

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index a953d4975b8c..e4786eeca38f 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1033,7 +1033,7 @@ i915_gem_execbuffer_move_to_active(struct list_head
*vmas,
                u32 old_write = obj->base.write_domain;

                obj->dirty = 1; /* be paranoid  */
-               obj->base.write_domain = obj->base.pending_write_domain;
+               obj->base.write_domain = I915_GEM_DOMAIN_RENDER;
                if (obj->base.write_domain == 0)
                        obj->base.pending_read_domains |=
obj->base.read_domains;
                obj->base.read_domains = obj->base.pending_read_domains;

would disable the optimisation and hide the libva bug. Does that fix your hang?

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