drm/i915: Workaround incoherence with fence updates on Valleyview
In commit 25ff1195 Author: Chris Wilson <chris@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: NJon Bloomfield <jon.bloomfield@intel.com> Tested-by: NJon Bloomfield <jon.bloomfield@intel.com> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62191Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
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