Re: [PATCH 2/2] drm/i915: catch gtfifo errors on forcewake_put

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, Feb 03, 2012 at 11:10:09PM +0000, Chris Wilson wrote:
> On Fri,  3 Feb 2012 14:31:41 -0800, Ben Widawsky <ben@bwidawsk.net> wrote:
> > This is similar to a patch I wrote several months ago. It's been updated
> > for the new FORCEWAKE_MT, and it also no longer clears the debug
> > register as it may be helpful to get that for the error state.  Also
> > recommended by Chris Wilson, use WARN() instead of DRM_ERROR, so we can
> > get a backtrace.
> > 
> > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> 
> Can we use the read of GTFIFODBG in place of the POSTING_READ? And do we
> really need to watch all the GTFIFODBG reads in the trace, or can I
> squelch that noise with a I915_READ_NOTRACE?
> -Chris

TBH, I don't really understand POSTING_READ that well. If it just
requires that any read request made it through to the MCH (or whatever),
then sure I can replace the POSTING_READ. Obviously though this is
reading GTFIFODBG, and not FORCEWAKE, so you tell me.

As for READ_NOTRACE, I'm all for that. I'll wait to reroll the patch
until you respond to the above though.