linux-kernel - Re: [PATCH] drivers: mfd: da9063: Add restart notifier implementation

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Message-ID: <CA+zEjCvFO6Tz+D42wgnstx_TLNEt=HM0eeT5g0-zwaEscGj2vQ@mail.gmail.com>
Date:   Wed, 6 Oct 2021 13:35:35 +0200
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     David Abdurachmanov <david.abdurachmanov@...il.com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Lee Jones <lee.jones@...aro.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: mfd: da9063: Add restart notifier implementation

On Wed, Oct 6, 2021 at 11:30 AM Adam Thomson
<Adam.Thomson.Opensource@...semi.com> wrote:
>
> On 05 October 2021 14:43, Alexandre Ghiti wrote:
>
> > > > > Thanks for the pointer! I have just tested this sequence from the
> > > > > u-boot shell, it resets the board correctly. But then if we try to
> > > > > power down the board by a long press to the corresponding button on
> > > > > the board within 16 seconds, it resets the board: so we cannot
> > > > > shutdown the board in the next 16 seconds that follow this sequence.
> > > > >
> > > > > Maybe that can be resolved by using the one-shot alarm as described by
> > > > > Adam, I'll try to find that in the datasheet.
> > > >
> > > > After configuring the one-shot alarm, I still have those intempestive
> > > > reboots if I try to power down the board by a long press within 16
> > > > seconds. The only thing I found in the datasheet regarding this timing
> > > > is in case of power undervoltage, not sure how this is linked to what
> > > > I see.
> > > >
> > > > @Adam Thomson Any ideas?
> > >
> > > Nothing immediately springs to mind. Can you confirm this is the nONKEY long
> > > press that you're attempting here, which is resetting the board rather than
> > > shutting down?
> >
> > Yes, this is the nONKEY long press that, if done within ~16sec after
> > the board is reset using the alarm, resets the board instead of
> > shutting it down.
> >
> > >
> > > Also, would you able to again provide events and fault log when this unwanted
> > > reset occurs, just in case there's anything there to give a clue. Can then
> > > discuss internally to see if we can ascertain what might be happening here.
> >
> > FAULT_LOG = 0x60
> > EVENT_A = 0x12
> > EVENT_B to EVENT_D = 0
> >
> > But I'm unsure of those values since they are the same after the reset
> > triggered by the one-shot alarm *and* if I clear EVENT_A, the
> > intempestive reboot does not appear!
>
> Thanks for the info. So we believe, based on the event registers values
> provided, it is the RTC event as that's not cleared by a power-cycle (it's in
> the always-on domain). The other test would be to mask this event immediately
> after an RTC based reboot and see if the long key-press then shuts down the
> device. I suspect it would in that case, as per you clearing the event.

Indeed if I mask the RTC alarm in IRQ_MASK_A, the intempestive reboot
disappears. But that's not something we can do: the reset driver will
actually be implemented in openSBI at some point where the devices are
probed on-demand (the same applies to u-boot I think), so we cannot
clear or mask anything at boot.

>
> I'm still curious as to the 16 seconds though. Would that be when the kernel
> finally starts and masks/clears events (seems quite a long time)?

No, the kernel is not up yet. Maybe 16sec is not the right value, I
may have been influenced by the discussion here
https://www.dialog-semiconductor.com/products/pmics?post_id=10052#tab-support_tab_content.

It seems there is some consensus about having this reset driver be a
SiFive Unmatched board specific thing: quid of the sequence I propose
in this patch then? It does not mess with the RTC registers, it
reboots reliably and there's no intempestive reboot: is it dangerous
to use? Or do you have another alternative?

Thanks,

Alex