Re: [PATCH] drm/i915: Restore the wait for idle engine after flushing interrupts

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

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

> So it appears that commit 5427f207852d ("drm/i915: Bump wait-times for
> the final CS interrupt before parking") was a little over optimistic in
> its belief that it had successfully waited for all residual activity on
> the engines before parking. Numerous sightings in CI since then of
>
> <7>[   52.542886] [IGT] core_auth: executing
> <3>[   52.561013] [drm:intel_engines_park [i915]] *ERROR* vcs0 is not idle before parking
> <7>[   52.561215] intel_engines_park vcs0
> <7>[   52.561229] intel_engines_park 	current seqno 98, last 98, hangcheck 0 [-247449 ms], inflight 0
> <7>[   52.561238] intel_engines_park 	Reset count: 0
> <7>[   52.561266] intel_engines_park 	Requests:
> <7>[   52.561363] intel_engines_park 	RING_START: 0x00000000 [0x00000000]
> <7>[   52.561377] intel_engines_park 	RING_HEAD:  0x00000000 [0x00000000]
> <7>[   52.561390] intel_engines_park 	RING_TAIL:  0x00000000 [0x00000000]
> <7>[   52.561406] intel_engines_park 	RING_CTL:   0x00000000
> <7>[   52.561422] intel_engines_park 	RING_MODE:  0x00000200 [idle]
> <7>[   52.561442] intel_engines_park 	ACTHD:  0x00000000_00000000
> <7>[   52.561459] intel_engines_park 	BBADDR: 0x00000000_00000000
> <7>[   52.561474] intel_engines_park 	Execlist status: 0x00000301 00000000
> <7>[   52.561489] intel_engines_park 	Execlist CSB read 5 [5 cached], write 5 [5 from hws], interrupt posted? no
> <7>[   52.561500] intel_engines_park 		ELSP[0] idle
> <7>[   52.561510] intel_engines_park 		ELSP[1] idle
> <7>[   52.561519] intel_engines_park 		HW active? 0x0
> <7>[   52.561608] intel_engines_park Idle? yes
> <7>[   52.561617] intel_engines_park
>
> on Braswell, which indicates that the engine just needs that little bit
> longer after flushing the tasklet to settle. So give it a few more
> milliseconds before declaring an emergency and applying the emergency
> brake.
>

Because the print above indicates that it did went idle straight
afterwards?

Just pondering here what was the key nonidleness key that
lead to this. What raced?

-Mika


> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103479
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_engine_cs.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 6cb8e3ed97e4..87778f03393b 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -1626,11 +1626,12 @@ void intel_engines_park(struct drm_i915_private *i915)
>  		 * will be no more interrupts arriving later and the engines
>  		 * are truly idle.
>  		 */
> -		if (!intel_engine_is_idle(engine)) {
> +		if (wait_for(intel_engine_is_idle(engine), 10)) {
>  			struct drm_printer p = drm_debug_printer(__func__);
>  
> -			DRM_ERROR("%s is not idle before parking\n",
> -				  engine->name);
> +			dev_err(i915->drm.dev,
> +				"%s is not idle before parking\n",
> +				engine->name);
>  			intel_engine_dump(engine, &p);
>  		}
>  
> -- 
> 2.15.0
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