[Intel-gfx] [PATCH 2/2] drm/i915/skl: Fix spurious gpu hang with gt3/gt4 revs

[Ben Widawsky]

On Tue, Apr 05, 2016 at 03:56:17PM +0300, Mika Kuoppala wrote:
> Experiments with heaven 4.0 benchmark and skylake gt3e (rev 0xa)
> suggest that WaForceContextSaveRestoreNonCoherent is needed for all
> revs. Extending this to all revs cures a gpu hang with rev 0xa when
> running heaven4.0 gpu benchmark.
> 
> We have been here before, with problems enabling gt4e and extending
> up to revision F0 instead of false claims of bspec of E0 only. See
> commit <e238659ddd88> ("drm/i915/skl: Default to noncoherent access
> up to F0"). In retrospect we should have covered this with this big
> blanket back then already, as E0 vs F0 discrepancy was suspicious
> enough.
> 
> Previously the WaForceEnableNonCoherent has been tied to
> context non-coherence, atleast in relevant hsds. So keep this tie
> and extended this alongside.
> 
> Cc: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> Cc: Ben Widawsky <benjamin.widawsky at intel.com>
> Cc: Timo Aaltonen <tjaalton at ubuntu.com>
> Cc: stable at vger.kernel.org
> Reported-by: Mike Lothian <mike at fireburn.co.uk>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=93491
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>

I don't have a reproducible hang, but both are:
Reviewed-by: Ben Widawsky <benjamin.widawsky at intel.com>

-- 
Ben Widawsky, Intel Open Source Technology Center