Re: [PATCH] drm/i915: Drop the overzealous warning from i915_gem_set_cache_level

Chris Wilson
2013-08-12T21:30:04Z

On Mon, Aug 12, 2013 at 02:02:09PM -0700, Ben Widawsky wrote:
> On Mon, Aug 12, 2013 at 11:46:17AM +0100, Chris Wilson wrote:
> > By our earlier reckoning, move from a snooped/llc setting to an uncached
> > setting, leaves the CPU cache in a consistent state irrespective of our
> > domain tracking - so we can forgo the warning about the lack of
> > invalidation. Similarly for any writes posted to the snooped CPU domain,
> > we know will be safely clflushed to the uncached PTEs after forcing the
> > domain change.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> I ran into this several times while doing the PPGTT development, and was
> always scared to just remove it. Does it make sense to keep the
> write_domain assertion with this gone?

I think we've justified in the earlier series why we can drop the
WARN_ON(write) with impunity. As we don't need to do so immediately, I'd
like to sleep on it for a while.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre