Re: [PATCH 1/2] include: trace: Add SCMI header with trace events

[Lukasz Luba]

On 12/20/19 4:24 PM, Jim Quinlan wrote:
> > Thank you for sharing your experiments and thoughts. I have probably
> > similar setup for stressing the communication channel, but I do also
> > some wired things in the firmware. That's why I need to measure these
> > delays. I am happy that it is useful for you also.
> >
> > I don't know if your firmware supports 'fast channel', but please keep
> > in mind that it is not tracked in this 'transfer_id'.
> > This transfer_id in v2 version does not show the real transfers
> > to the firmware since there is another path called 'fast channel' or
> > 'fast_switch' in the CPUfreq. It is in drivers/firmware/arm_scmi/perf.c
> > and the atomic variable is not incremented in that path. Adding it also
> > there just for atomic_inc() probably would add delays in the fast_switch
> > and also brings little value.
> > For the normal channel, where we have spinlocks and other stuff, this
> > atomic_inc() could stay in my opinion.
> >
> > Regards,
> > Lukasz
> Hi Lukasz,
>
> We currently do not use "fast channels" - although it is possible we might someday.
> I find the transfer_id useful per your v2 even if it doesn't cover FC. Thanks for
> submitting and discussing this!

Thank you for cooperation.

Regards,
Lukasz

> Regards,
> Jim Quinlan