Re: [Intel-gfx] [PATCH 15/22] drm/i915/guc: Flush G2H work queue during reset

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Aug 16, 2021 at 06:51:32AM -0700, Matthew Brost wrote:
> It isn't safe to scrub for missing G2H or continue with the reset until
> all G2H processing is complete. Flush the G2H work queue during reset to
> ensure it is done running.
> 
> Fixes: eb5e7da736f3 ("drm/i915/guc: Reset implementation for new GuC interface")
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  .../gpu/drm/i915/gt/uc/intel_guc_submission.c  | 18 ++----------------
>  1 file changed, 2 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 3a01743e09ea..8c560ed14976 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -707,8 +707,6 @@ static void guc_flush_submissions(struct intel_guc *guc)
>  
>  void intel_guc_submission_reset_prepare(struct intel_guc *guc)
>  {
> -	int i;
> -
>  	if (unlikely(!guc_submission_initialized(guc))) {
>  		/* Reset called during driver load? GuC not yet initialised! */
>  		return;
> @@ -724,20 +722,8 @@ void intel_guc_submission_reset_prepare(struct intel_guc *guc)
>  
>  	guc_flush_submissions(guc);
>  
> -	/*
> -	 * Handle any outstanding G2Hs before reset. Call IRQ handler directly
> -	 * each pass as interrupt have been disabled. We always scrub for
> -	 * outstanding G2H as it is possible for outstanding_submission_g2h to
> -	 * be incremented after the context state update.
> -	 */
> -	for (i = 0; i < 4 && atomic_read(&guc->outstanding_submission_g2h); ++i) {
> -		intel_guc_to_host_event_handler(guc);
> -#define wait_for_reset(guc, wait_var) \
> -		intel_guc_wait_for_pending_msg(guc, wait_var, false, (HZ / 20))
> -		do {
> -			wait_for_reset(guc, &guc->outstanding_submission_g2h);
> -		} while (!list_empty(&guc->ct.requests.incoming));
> -	}
> +	flush_work(&guc->ct.requests.worker);

Same thing about flush_work as in an earlier patch.
-Daniel

> +
>  	scrub_guc_desc_for_outstanding_g2h(guc);
>  }
>  
> -- 
> 2.32.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch