[Intel-gfx] [PATCH] drm/i915: Stop engines before reset

[Mika Kuoppala]

Mika Kuoppala <mika.kuoppala at linux.intel.com> writes:

> On kbl 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 ack for readiness,
> still can cause a system hang.
>
> We also have similar experiences on older gens. So now
> attempt to stop engines before proceeding for reset, on all
> gens where we have a gpu reset. This has shown to improve reset
> reliability and reduce the risk of losing the machine.
>
> v2: Add fixme for wa (Joonas)
>
> Testcase: igt/prime_busy/hang-* # kbl
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
> Acked-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Pushed, thanks for acks.
-Mika