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

[Alexandre Ghiti]

Hi David,

On Thu, Sep 30, 2021 at 9:51 AM David Abdurachmanov
<david.abdurachmanov at gmail.com> wrote:
>
> On Wed, Sep 29, 2021 at 4:36 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.
>
> Today I was looking into OpenBSD DA9063 drivers and they might be
> doing what you described for the reset.
>
> dev/fdt/dapmic.c
>
> [..]
> 241 void
> 242 dapmic_reset(void)
> 243 {
> 244     struct dapmic_softc *sc = dapmic_cd.cd_devs[0];
> 245     uint8_t reg;
> 246
> 247     /* Enable tick alarm wakeup with a one second interval. */
> 248     reg = dapmic_reg_read(sc, ALARM_MO);
> 249     reg &= ~ALARM_MO_TICK_TYPE;
> 250     reg |= ALARM_MO_TICK_WAKE;
> 251     dapmic_reg_write(sc, ALARM_MO, reg);
> 252
> 253     /* Enable tick function. */
> 254     reg = dapmic_reg_read(sc, ALARM_Y);
> 255     reg |= ALARM_Y_TICK_ON;
> 256     dapmic_reg_write(sc, ALARM_Y, reg);
> 257
> 258     /* Clear events such that we wake up again. */
> 259     dapmic_reg_write(sc, EVENT_A, dapmic_reg_read(sc, EVENT_A));
> 260     dapmic_reg_write(sc, CONTROL_F, CONTROL_F_SHUTDOWN);
> 261 }
> [..]
>

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.

Thanks

Alex

> >
> > 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.
>
> Agree. Currently it seems Linux drivers expect DA9063 boards to have
> AUTOBOOT ON set in OTP, which is not the case for SiFive Unmatched
> (thus issues with reset and WDT).
>
> david
>
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