[PATCH 17/27] drm/i915/guc: Flush G2H work queue during reset

[Daniele Ceraolo Spurio]

On 8/24/2021 8:44 AM, Matthew Brost wrote:
> On Fri, Aug 20, 2021 at 05:25:41PM -0700, Daniele Ceraolo Spurio wrote:
>>
>> On 8/18/2021 11:16 PM, 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.
>> Might be worth moving this patch closer to "drm/i915/guc: Process all G2H
>> message at once in work queue".
>>
> Sure.
>
>>> Fixes: eb5e7da736f3 ("drm/i915/guc: Reset implementation for new GuC interface")
>>> Signed-off-by: Matthew Brost <matthew.brost at 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 4cf5a565f08e..9a53bae367b1 100644
>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>> @@ -714,8 +714,6 @@ 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;
>>> @@ -731,20 +729,8 @@ 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);
>>> +
>> We're now not waiting in the requests anymore, just ensuring that the
>> processing of the ones we already received is done. Is this intended? We do
>> still handle the remaining oustanding submission in the scrub so it's
>> functionally correct, but the commit message doesn't state the change in
>> waiting behavior, so wanted to double check it was planned.
>>
> Yes, it is planned as scrub code should be able to cope with any missing
> G2H. Will update the commit message to reflect that.

With the updated commit msg:

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>

Daniele

>
> Matt
>
>> Daniele
>>
>>>    	scrub_guc_desc_for_outstanding_g2h(guc);
>>>    }