[Intel-gfx] [PATCH 2/2] drm/i915/guc: Allow for very slow GuC loading

[Dixit, Ashutosh]

On Fri, 10 Mar 2023 17:01:42 -0800, John Harrison wrote:
>
> >> +	for (count = 0; count < 20; count++) {
> >> +		ret = wait_for(guc_load_done(uncore, &status, &success), 1000);
> >
> > Isn't 20 secs a bit too long for an in-place wait? I get that if the GuC
> > doesn't load (or fail to) within a few secs the HW is likely toast, but
> > still that seems a bit too long to me. What's the worst case load time
> > ever observed? I suggest reducing the wait to 3 secs as a compromise, if
> > that's bigger than the worst case.
>
> I can drop it to 3 for normal builds and keep 20 for
> CONFIG_DRM_I915_DEBUG_GEM builds. However, that won't actually be long
> enough for all slow situations. We have seen times of at least 11s when the
> GPU is running at minimum frequency. So, for CI runs we definitely want to
> keep the 20s limit. For end users? Is it better to wait for up to 20s or to
> boot in display only fallback mode? And note that this is a timeout only. A
> functional system will still complete in tens of milliseconds.

Just FYI, in this related patch:

https://patchwork.freedesktop.org/series/115003/#rev2

I am holding a mutex across GuC FW load, so very unlikely, but worst case a
thread can get blocked for the duration of the GuC reset/FW load.

Ashutosh