Re: [PATCH v4] drm/i915 : Added Programming of the MOCS

Antoine, Peter
2015-06-18T08:04:37Z

-----Original Message-----
From: Chris Wilson [mailto:chris@chris-wilson.co.uk]
Sent: Thursday, June 18, 2015 8:42 AM
To: Daniel Vetter
Cc: Antoine, Peter; intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH v4] drm/i915 : Added Programming of the MOCS

On Thu, Jun 18, 2015 at 08:59:55AM +0200, Daniel Vetter wrote:
> > + /*
> > + * Failing to program the MOCS is non-fatal.The system will not
> > + * run at peak performance. So generate a warning and carry on.
> > + */
>
> Is this really true? Userspace must make sure that they don't
> inappropriately overwrite the caching settings using MOCS for
> frontbuffers and in doing so causing coherency issues with the display
> block. If we fail to program MOCS correctly then things won't look pretty.

I was under the presumption that the MOCS entries would default to UC, since that is the failsafe mode.
-Chris

No they will stay at the hardware defaults as specified in the Bspec.
Peter.

--
Chris Wilson, Intel Open Source Technology Centre