[Intel-gfx] [PATCH] drm/i915: Workaround incoherence with fence updates on Valleyview

[Daniel Vetter]

On Wed, May 22, 2013 at 05:08:06PM +0100, Chris Wilson wrote:
> In commit 25ff1195f8a0b3724541ae7bbe331b4296de9c06
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Thu Apr 4 21:31:03 2013 +0100
> 
>     drm/i915: Workaround incoherence between fences and LLC across multiple CPUs
> 
> we introduced an empirical workaround for memory corruption when using
> fences from multiple CPUs. At the time, we did not have any results for
> Valleyview, so the presumption was that it was limited to recent
> generations using LLC. Now we have evidence that Valleyview also suffers
> incoherence and requires a similar but different workaround. For
> Valleyview, the wbinvd instruction is insufficient and we require the
> serialising register write per-CPU. Conversely, that serialising
> register write is not enough for SNB/IVB/HSW. To compromise and keep the
> code relatively clean, employ both serialisation techniques in the same
> workaround.
> 
> Reported-by: Jon Bloomfield <jon.bloomfield at intel.com>
> Tested-by: Jon Bloomfield <jon.bloomfield at intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62191
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Queued for -next (since vlv isn't yet declared stable in 3.10), thanks for
the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch