Re: [Intel-gfx] [PATCH v2] drm/i915/selftests: Flush the old heartbeat more gently

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

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

> In order to test how fast the heartbeat can respond, we measure with the
> interval set to its minimum. Before we measure though, we want to be
> sure we start with a fresh pulse, and so wait until any old one is
> complete. During that wait though, we were continually flushing the
> work, and so continually re-evaluating to see if the pulse was complete,
> and each attempt would count as an unresponsive system. If the engine
> did not complete the request in the couple of busy-spins, it would flag
> an error. This is unfortunate, so let's not busy-spin waiting for the
> old heartbeat, but terminate it and start afresh.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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

> ---
>  drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
> index e73854dd2fe0..b88aa35ad75b 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c
> @@ -215,16 +215,17 @@ static int __live_heartbeat_fast(struct intel_engine_cs *engine)
>  		goto err_pm;
>  
>  	for (i = 0; i < ARRAY_SIZE(times); i++) {
> -		/* Manufacture a tick */
>  		do {
> -			while (READ_ONCE(engine->heartbeat.systole))
> -				flush_delayed_work(&engine->heartbeat.work);
> +			/* Manufacture a tick */
> +			intel_engine_park_heartbeat(engine);
> +			GEM_BUG_ON(engine->heartbeat.systole);
> +			engine->serial++; /*  pretend we are not idle! */
> +			intel_engine_unpark_heartbeat(engine);
>  
> -			engine->serial++; /* quick, pretend we are not idle! */
>  			flush_delayed_work(&engine->heartbeat.work);
>  			if (!delayed_work_pending(&engine->heartbeat.work)) {
> -				pr_err("%s: heartbeat did not start\n",
> -				       engine->name);
> +				pr_err("%s: heartbeat %d did not start\n",
> +				       engine->name, i);
>  				err = -EINVAL;
>  				goto err_pm;
>  			}
> -- 
> 2.20.1
>
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