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

[Adam Thomson]

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.