Re: [Intel-gfx] [PATCH] drm/i915/gt: Scrub HW state on remove

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Currently we do a final scrub of the HW state upon release. However,
> when rebinding the device, this is too late as the device may either
> have been partially rebound or the device is no longer accessible. If
> the device has been removed before release, the reset goes astray
> leaving the device in an inconsistent state, unlikely to work without a
> full PCI reset. Furthermore, if the device is partially rebound before
> the HW scrubbing, there may be leftover HW state that should have been
> scrubbed. Either way, we need to push the scrubbing earlier before the
> removal, so into unregister. The danger is that on older machines,
> reseting the GPU also impact the display engine and so the reset should
> be after modesetting is disabled (and before reuse we need to recover
> modesetting).
>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2508
> Testcase: igt/core_hotunplug
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 39b428c5049c..44f1d51e5ae5 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -614,6 +614,8 @@ void intel_gt_driver_remove(struct intel_gt *gt)
>  
>  void intel_gt_driver_unregister(struct intel_gt *gt)
>  {
> +	intel_wakeref_t wakeref;
> +
>  	intel_rps_driver_unregister(&gt->rps);
>  
>  	/*
> @@ -622,16 +624,15 @@ void intel_gt_driver_unregister(struct intel_gt *gt)
>  	 * resources.
>  	 */
>  	intel_gt_set_wedged(gt);
> +
> +	/* Scrub all HW state upon release */
> +	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
> +		__intel_gt_reset(gt, ALL_ENGINES);
>  }
>  
>  void intel_gt_driver_release(struct intel_gt *gt)
>  {
>  	struct i915_address_space *vm;
> -	intel_wakeref_t wakeref;
> -
> -	/* Scrub all HW state upon release */
> -	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
> -		__intel_gt_reset(gt, ALL_ENGINES);
>  
>  	vm = fetch_and_zero(&gt->vm);
>  	if (vm) /* FIXME being called twice on error paths :( */
> -- 
> 2.20.1
>
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