[Intel-gfx] [PATCH 2/2] drm/i915/gt: Only unwedge if we can reset first

[Janusz Krzysztofik]

Hi Chris,

On Tuesday, September 10, 2019 12:55:36 AM CEST Chris Wilson wrote:
> Unwedging the GPU requires a successful GPU reset before we restore the
> default submission, or else we may see residual context switch events
> that we were not expecting.
> 
> Reported-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_reset.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/
gt/intel_reset.c
> index fe57296b790c..5242496a893a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -809,6 +809,7 @@ static bool __intel_gt_unset_wedged(struct intel_gt *gt)
>  	struct intel_gt_timelines *timelines = &gt->timelines;
>  	struct intel_timeline *tl;
>  	unsigned long flags;
> +	bool ok;
>  
>  	if (!test_bit(I915_WEDGED, &gt->reset.flags))
>  		return true;
> @@ -854,7 +855,11 @@ static bool __intel_gt_unset_wedged(struct intel_gt 
*gt)
>  	}
>  	spin_unlock_irqrestore(&timelines->lock, flags);
>  
> -	intel_gt_sanitize(gt, false);
> +	ok = false;
> +	if (!reset_clobbers_display(gt->i915))
> +		ok = __intel_gt_reset(gt, ALL_ENGINES) == 0;
> +	if (!ok)
> +		return false;

Before your change, that code was executed inside intel_gt_sanitize(gt, false) 
which unfortunately didn't return any result.  The same outcome could be 
achieved by redefining intel_gt_sanitize() to return that result and saying:

	if (!intel_gt_sanitize(gt, false)
		return false;

Is there any specific reason for intel_gt_sanitize() returning void?

Thanks,
Janusz

>  
>  	/*
>  	 * Undo nop_submit_request. We prevent all new i915 requests from
>