Re: [Intel-gfx] [PATCH] drm/i915/huc: bump timeout for delayed load and reduce print verbosity

["Ceraolo Spurio, Daniele" <daniele.ceraolospurio@xxxxxxxxx>]

On 10/6/2022 1:09 PM, John Harrison wrote:
> On 10/6/2022 10:20, Daniele Ceraolo Spurio wrote:
> > We're observing sporadic HuC delayed load timeouts in CI, due to mei_pxp
> > binding completing later than we expected. HuC is still still loaded
> still still
>
> > when the bind occurs, but in the meantime i915 has started allowing
> > submission to the VCS engines even if HuC is not there.
> > In most of the cases I've observed, the timeout was due to the
> > init/resume of another driver between i915 and mei hitting errors and
> > thus adding an extra delay, but HuC was still loaded before userspace
> > could submit, because the whole resume process time was increased by the
> > delays.
> >
> > Given that there is no upper bound to the delay that can be introduced
> > by other drivers, I've reached the following compromise with the media
> > team:
> >
> > 1) i915 is going to bump the timeout to 5s, to reduce the probability
> > of reaching it. We still expect HuC to be loaded before userspace
> > starts submitting, so increasing the timeout should have no impact on
> > normal operations, but in case something weird happens we don't want to
> > stall video submissions for too long.
> >
> > 2) The media driver will cope with the failing submissions that manage
> > to go through between i915 init/resume complete and HuC loading, if any
> > ever happen. This could cause a small corruption of video playback
> > immediately after a resume (we should be safe on boot because the media
> > driver polls the HUC_STATUS ioctl before starting submissions).
> >
> > Since we're accepting the timeout as a valid outcome, I'm also reducing
> > the print verbosity from error to notice.
> >
> > References: https://gitlab.freedesktop.org/drm/intel/-/issues/7033
> > Fixes: 27536e03271d ("drm/i915/huc: track delayed HuC load with a 
> > fence")
> > Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
> > Cc: Tony Ye <tony.ye@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/gt/uc/intel_huc.c | 10 ++++++----
> >   1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_huc.c 
> > b/drivers/gpu/drm/i915/gt/uc/intel_huc.c
> > index 4d1cc383b681..73a6a2fae637 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_huc.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_huc.c
> > @@ -52,10 +52,12 @@
> >    * guaranteed for this to happen during boot, so the big timeout is 
> > a safety net
> >    * that we never expect to need.
> >    * MEI-PXP + HuC load usually takes ~300ms, but if the GSC needs to 
> > be resumed
> > - * and/or reset, this can take longer.
> > + * and/or reset, this can take longer. Note that the kernel might 
> > schedule
> > + * other work between the i915 init/resume and the MEI one, which 
> > can add to
> > + * the delay.
> >    */
> >   #define GSC_INIT_TIMEOUT_MS 10000
> > -#define PXP_INIT_TIMEOUT_MS 2000
> > +#define PXP_INIT_TIMEOUT_MS 5000
> If we already have the GSC timeout at 10s, why not just use 10s for 
> PXP as well?

They're different type of operations: mei_gsc is a full on aux driver, 
so it is loaded only once during boot; mei_pxp is a component and it is 
bound on init and then unbound/re-bound on suspend/resume. On resume we 
don't want timeouts excessively big.

> >     static int sw_fence_dummy_notify(struct i915_sw_fence *sf,
> >                    enum i915_sw_fence_notify state)
> > @@ -104,8 +106,8 @@ static enum hrtimer_restart 
> > huc_delayed_load_timer_callback(struct hrtimer *hrti
> >       struct intel_huc *huc = container_of(hrtimer, struct intel_huc, 
> > delayed_load.timer);
> >         if (!intel_huc_is_authenticated(huc)) {
> > -        drm_err(&huc_to_gt(huc)->i915->drm,
> > -            "timed out waiting for GSC init to load HuC\n");
> > +        drm_notice(&huc_to_gt(huc)->i915->drm,
> > +               "timed out waiting for GSC init to load HuC\n");
> If the failure is that the MEI PXP module hasn't loaded yet, why is 
> the error message 'waiting for GSC init'? Or can we not distinguish 
> between GSC load timeout and PXP load timeout? In which case should 
> the message refer to 'GSC/PXP'?

I wanted to keep things simple and have a unified message for both 
scenarios as what we care about from an i915 POV is that something went 
wrong on the mei side. I can split it up.

Daniele

> John.
>
> >             __gsc_init_error(huc);
> >       }