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

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Message-ID: <CA+zEjCv8tExoZx309qRMe6KCZ=-AC+nCOV7qivJWE5gCqrd2MA@mail.gmail.com>
Date:   Thu, 30 Sep 2021 11:55:16 +0200
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     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

Hi Adam,

Thank you for your answer.

On Wed, Sep 29, 2021 at 3:33 PM Adam Thomson
<Adam.Thomson.Opensource@...semi.com> wrote:
>
> On 24 September 2021 17:17, Alexandre Ghiti wrote:
>
> > > > +static int da9063_restart_notify(struct notifier_block *this,
> > > > +                              unsigned long mode, void *cmd)
> > > > +{
> > > > +     struct da9063 *da9063 = container_of(this, struct da9063,
> > > > restart_handler);
> > > > +
> > > > +     regmap_write(da9063->regmap, DA9063_REG_PAGE_CON, 0x00);
> > > > +     regmap_write(da9063->regmap, DA9063_REG_CONTROL_F, 0x04);
> > > > +     regmap_write(da9063->regmap, DA9063_REG_CONTROL_A, 0x68);
> > > > +
> > > > +     return NOTIFY_DONE;
> > > > +}
> > >
> > > I will talk with our HW team to clarify, but this sequence looks to be very
> > > specific to the needs of the platform in question which doesn't feel right to
> > > me. As was mentioned on another thread as well, the watchdog driver already
> > has
> > > a restart function to reset the device (and thus the system), so I don't believe
> > > we should have multiple of these.
> >
> > From the discussion that happened here
> > https://www.dialog-semiconductor.com/products/pmics?post_id=10052#tab-
> > support_tab_content,
> > it does not seem possible to use the watchdog on a chip whose OTP does
> > not set AUTOBOOT. But anyway, I'm looking forward to hearing from the
> > HW team :)
>
> So I've discussed this internally and so far it's not completely clear how the
> sequence you provided actually performs the reset as you suggest. It certainly
> doesn't look like it should, so maybe this relates to an external pin somehow
> triggering the restart in this particular scenario? I'd be interested to
> understand which event bits are set when the board does restart to understand
> what did actually trigger the boot-up.

After clearing all those registers and a reset as done in this patch,
I get the following values:

FAULT_LOG: 0x00
EVENT_A: 0x10 => As per the datasheet, "Sequencer reached final
position caused event" ?
EVENT_B: 0x00
EVENT_C: 0x00
EVENT_D: 0x00

Do you need any other info?

>
> Regardless of this though, the consensus right now would be to use the RTC as a
> wake event to restart the platform. An alarm can be set for a couple of seconds
> into the future (or longer if required) and that would provide the event
> required to come up from powerdown/shutdown, in the absence of AUTOBOOT being
> set in OTP. I believe this would be the safest route to take in this case. You
> can then just use the SHUTDOWN bit on CONTROL_F to take down the board.
>
> To reiterate, I believe this should be made a board specific quirk, rather than
> as part of the generic MFD core of DA9063, as the timings may vary for other
> platforms.

Alex