[Intel-gfx] [PATCH] drm/i915: Stop ring before doing readiness check

[Chris Wilson]

Quoting Mika Kuoppala (2017-09-13 15:01:17)
> Evidence indicates that even if the hardware happily
> tells us to proceed with reset, it really isn't ready.
> Resetting a freely running batchbuffer after we have
> got ack for readiness, still can cause a system hang.

Hmm, so we see it on early gen and late gen. I suggest we do it
universally (except gen2 which is lacking the mechanism). It's unlikely
that the requirement disappeared just for a couple of gen, more likely
that we simply haven't triggered the pathological behaviour.

Other than,
Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
for the find.
-Chris