[PATCH] drm/i915/gt: Add a delay to let engine resumes correctly

[Krzysztof Karas]

Hi Nitin,

[...]
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13650
[...]

>  			     ENGINE_READ_FW(engine, RING_START));
> +		/*
> +		 * Sometimes engine head failed to set to zero even after writing into it.
> +		 * Use 20ms delay to let engine resumes from correct RING_HEAD.
> +		 * Experimented different values and determined that 20ms works best
> +		 * based on testing.
> +		 */
> +		mdelay(20);
Since we do not propagate the errors returned from `stop_ring()`
function and the linked issue is not a failure, because the
subtest succeeds, I wonder if we could lower the severity of
this log to a warning.

Regardless of whether you consider my suggestion or not, the
patch looks good to me:

Reviewed-by: Krzysztof Karas <krzysztof.karas at intel.com>

Best Regards,
Krzysztof