Re: [PATCH 2/2] drm/i915: Force reset on unready engine

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Mika Kuoppala <mika.kuoppala@linux.intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/2] drm/i915: Force reset on unready engine
Date: Mon, 13 Aug 2018 11:51:37 +0100	[thread overview]
Message-ID: <153415749735.32460.7952471241443371408@skylake-alporthouse-com> (raw)
In-Reply-To: <20180813104242.32651-1-mika.kuoppala@linux.intel.com>

Quoting Mika Kuoppala (2018-08-13 11:42:42)
> If engine reports that it is not ready for reset, we
> give up. Evidence shows that forcing a per engine reset
> on an engine which is not reporting to be ready for reset,
> can bring it back into a working order. There is risk that
> we corrupt the context image currently executing on that
> engine. But that is a risk worth taking as if we unblock
> the engine, we prevent a whole device wedging in a case
> of full gpu reset.
> 
> Reset individual engine even if it reports that it is not
> prepared for reset, but only if we aim for full gpu reset
> and not on first reset attempt.
> 
> v2: force reset only on later attempts, readability (Chris)
> v3: simplify with adequate caffeine levels (Chris)
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

One last thing, you said you recalled one of the reasons for its
existence was to prevent machine lockups on kbl. Is the recollection
true? Do we want to leave a comment in case of fire?
-Chris
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