[Intel-gfx] [PATCH] drm/i915: Restore the kernel context after a GPU reset on an idle engine

[Michel Thierry]

On 12/15/2017 4:03 PM, Chris Wilson wrote:
> As part of the system requirement for powersaving is that we always have
> a context loaded. Upon boot and resume, we load the kernel_context to
> ensure that some valid state is set before powersaving kicks in, we
> should do so after a full GPU reset as well. We only need to do so for
> an idle engine, as any active engines will restart by executing the
> stuck request, loading its context, for the idle engine we create a
> new request to load the kernel_context instead.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 4a7f5579a7a5..189725a8fed6 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3119,6 +3119,15 @@ void i915_gem_reset(struct drm_i915_private *dev_priv)
>                  ctx = fetch_and_zero(&engine->last_retired_context);
>                  if (ctx)
>                          engine->context_unpin(engine, ctx);
> +
> +               if (list_empty(&engine->timeline->requests)) {
> +                       struct drm_i915_gem_request *rq;
> +
> +                       rq = i915_gem_request_alloc(engine,
> +                                                   dev_priv->kernel_context);
> +                       if (!IS_ERR(rq))
> +                               __i915_add_request(rq, false);
> +               }
>          }
> 
>          i915_gem_restore_fences(dev_priv);

It shouldn't hurt and if it fixes something,

Reviewed-by: Michel Thierry <michel.thierry at intel.com>