[PATCH] drivers: mfd: da9063: Add restart notifier implementation

[Alexandre Ghiti]

On Wed, Sep 29, 2021 at 3:33 PM Adam Thomson
<Adam.Thomson.Opensource at diasemi.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.
>
> 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.

What timings are you referring to? Is the timing you're talking to the
time between the shutdown and the tick that wakes the device up?

Because I have another series ready which uses a new device tree
binding so that platforms that want the reset from the DA9063 can ask
for it via the device tree. And then I could add a property "duration"
that is platform dependent.