From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH] drm/i915: add interface to simulate gpu
	hangs
Date: Sat, 5 May 2012 21:13:10 +0200
Message-ID: <20120505191310.GB4985@phenom.ffwll.local>
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To: Eugeni Dodonov <eugeni@dodonov.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>
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On Thu, May 03, 2012 at 04:00:00PM -0300, Eugeni Dodonov wrote:
> On Thu, May 3, 2012 at 9:48 AM, Daniel Vetter <daniel.vetter@ffwll.ch>wrote:
> 
> > gpu reset is a very important piece of our infrastructure.
> > Unfortunately we only really it test by actually hanging the gpu,
> > which often has bad side-effects for the entire system. And the gpu
> > hang handling code is one of the rather complicated pieces of code we
> > have, consisting of
> > - hang detection
> > - error capture
> > - actual gpu reset
> > - reset of all the gem bookkeeping
> > - reinitialition of the entire gpu
> >
> > This patch adds a debugfs to selectively stopping rings by ceasing to
> > update the hw tail pointer, which will result in the gpu no longer
> > updating it's head pointer and eventually to the hangcheck firing.
> > This way we can exercise the gpu hang code under controlled conditions
> > without a dying gpu taking down the entire systems.
> >
> > Patch motivated by me forgetting to properly reinitialize ppgtt after
> > a gpu reset.
> >
> > Usage:
> >
> > echo $((1 << $ringnum)) > i915_ring_stop # stops one ring
> >
> > echo 0xffffffff > i915_ring_stop # stops all, future-proof version
> >
> > then run whatever testload is desired. i915_ring_stop automatically
> > resets after a gpu hang is detected to avoid hanging the gpu to fast
> > and declaring it wedged.
> >
> > v2: Incorporate feedback from Chris Wilson.
> >
> > v3: Add the missing cleanup.
> >
> > v4: Fix up inconsistent size of ring_stop_read vs _write, noticed by
> > Eugeni Dodonov.
> >
> > Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> >
> 
> Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>

I've slurped the hangman into -next, thanks for the review.
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48