RE: [RFC 0/7] cpuidle: Add poking mechanism to support non-IPI wakeup

Aisheng Dong
2019-03-28T11:27:59Z

[...]
> > > Anything that isn't visible to the GPC and requires the GIC
> > > wake_request signal to behave as specified is broken by this erratum.
> >
> > I really wonder how a timer interrupt (a PPI, hence not routed through
> > the GPC) can wake up the CPU in this case. It really feels like
> > something like "program CNTV_CVAL_EL0 to expire at some later point;
> > WFI" could result in the CPU going to a deep sleep state, and not
> > wake-up at all.
>
> I guess it's broken in the same way. The downstream DT claims
> "local-timer-stop" for the CPU sleep state and "arm,no-tick-in-suspend"
> for the armv8-timer, which I guess is not the timer actually stopping in suspend,
> but the CPU being unable to wake up due to the timer IRQ.
>
> > This would indicate that not only cpuidle is broken with this, but
> > absolutely every interrupt that is not routed through the GPC.
>
> That's my understanding as well. Note that I have no NXP internal information
> and can only infer from the published reference manual, errata notice and
> downstream kernel.
>

We will double check it.
Thanks for the information.

Regards
Dong Aisheng

> Regards,
> Lucas