linux-kernel - Re: [PATCH V1 1/1] soc: qcom: smp2p: Add wakeup capability to SMP2P IRQ

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Date:   Tue, 10 Aug 2021 21:25:01 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Sibi Sankar <sibis@...eaurora.org>,
        Deepak Kumar Singh <deesin@...eaurora.org>,
        clew@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH V1 1/1] soc: qcom: smp2p: Add wakeup capability to SMP2P IRQ

Quoting Bjorn Andersson (2021-08-10 16:11:10)
> On Tue 10 Aug 14:18 CDT 2021, Stephen Boyd wrote:
>
> > Quoting Sibi Sankar (2021-08-10 10:24:32)
> > > On 2021-08-09 23:28, Stephen Boyd wrote:
> > > > Quoting Deepak Kumar Singh (2021-08-09 04:05:08)
> > > >>
> > > >> On 8/6/2021 1:10 AM, Stephen Boyd wrote:
> > > >> > Quoting Deepak Kumar Singh (2021-08-05 09:17:33)
> > > >> >> Some use cases require SMP2P interrupts to wake up the host
> > > >> >> from suspend.
> > > >> > Please elaborate on this point so we understand what sort of scenarios
> > > >> > want to wakeup from suspend.
> > > >>
> > > >> Once such scenario is where WiFi/modem crashes and notifies crash to
> > > >> local host through smp2p
> > > >>
> > > >> if local host is in suspend it should wake up to handle the crash and
> > > >> reboot the WiFi/modem.
> > > >
> > > > Does anything go wrong if the firmware crashes during suspend and the
> > > > local host doesn't handle it until it wakes for some other reason? I'd
> > > > like to understand if the crash handling can be delayed/combined with
> > > > another wakeup.
> > >
> > > If the modem firmware crashes
> > > during suspend, the system comes
> > > out of xo-shutdown and AFAIK stays
> > > there until we handle the interrupt.
> > >
> >
> > So you're saying we waste power if we don't wakeup the AP and leave the
> > SoC in a shallow low power state? That would be good to have indicated
> > in the code via a comment and in the commit text so we know that we want
> > to handle the wakeup by default.
>
> Sounds like in a system without autosleep (or userspace equivalent) it
> would be desirable to leave the SoC in this lower state than to wake up
> the system handle the crash and then just idle?
>
> But leaving the system in this state will result in you missing your
> important phone calls...
>

Yes I think we should just add a comment to the code and commit text and
move on.