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

[Alexandre Ghiti <alexandre.ghiti@canonical.com>]

On Tue, Sep 21, 2021 at 1:33 PM Alexandre Ghiti
<alexandre.ghiti@canonical.com> wrote:
>
> On Tue, Sep 21, 2021 at 12:25 PM Ben Dooks <ben.dooks@codethink.co.uk> wrote:
> >
> > On 21/09/2021 06:33, Alexandre Ghiti wrote:
> > > The SiFive Unmatched board uses the da9063 PMIC for reset: add a restart
> > > notifier that will execute a small i2c sequence allowing to reset the
> > > board.
> > >
> > > The original implementation comes from Marcus Comstedt and Anders Montonen
> > > (https://forums.sifive.com/t/reboot-command/4721/28).
> > >
> > > Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
> >
> > I've got a couple of comments here, mainly is this the right place
> > and has anyone other than you tested. I tried something similar on
> > my Unmatched and it just turned the board off.
>
> Someone else in the thread I mention in the commit log tried it, but
> more feedback are welcome :)
>
> For the Unmatched, this solution will be temporary, the best place
> being openSBI which lacks i2c support for now.
> But I think this can be used by other boards using this PMIC.
>
> >
> > > ---
> > >   drivers/mfd/da9063-core.c       | 25 +++++++++++++++++++++++++
> > >   include/linux/mfd/da9063/core.h |  3 +++
> > >   2 files changed, 28 insertions(+)
> > >
> > > diff --git a/drivers/mfd/da9063-core.c b/drivers/mfd/da9063-core.c
> > > index df407c3afce3..c87b8d611f20 100644
> > > --- a/drivers/mfd/da9063-core.c
> > > +++ b/drivers/mfd/da9063-core.c
> > > @@ -20,6 +20,7 @@
> > >   #include <linux/mutex.h>
> > >   #include <linux/mfd/core.h>
> > >   #include <linux/regmap.h>
> > > +#include <linux/reboot.h>
> > >
> > >   #include <linux/mfd/da9063/core.h>
> > >   #include <linux/mfd/da9063/registers.h>
> > > @@ -158,6 +159,18 @@ static int da9063_clear_fault_log(struct da9063 *da9063)
> > >       return ret;
> > >   }
> > >
> > > +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;
> > > +}
> > > +
> >
> > Firstly, do you also need to force the AUTOBOOT (bit 3, CONTROL_C)
> > to ensure the PMIC does restart.
>
> I tried this too and actually, it seems that the value is read from
> OTP at reboot and as it is not set here, it has no effect.
>
> >
> > >   int da9063_device_init(struct da9063 *da9063, unsigned int irq)
> > >   {
> > >       int ret;
> > > @@ -197,6 +210,18 @@ int da9063_device_init(struct da9063 *da9063, unsigned int irq)
> > >               }
> > >       }
> > >
> > > +     da9063->restart_handler.notifier_call = da9063_restart_notify;
> > > +     da9063->restart_handler.priority = 128;
> > > +     ret = register_restart_handler(&da9063->restart_handler);
> > > +     if (ret) {
> > > +             dev_err(da9063->dev, "Failed to register restart handler\n");
> > > +             return ret;
> > > +     }
> > > +
> > > +     devm_add_action(da9063->dev,
> > > +                     (void (*)(void *))unregister_restart_handler,
> > > +                     &da9063->restart_handler);
> >
> > there's devm_register_reboot_notifier()
>
> Thanks for that!

Actually restart_notifier and reboot_notifier are not the same, see
https://elixir.bootlin.com/linux/latest/source/kernel/reboot.c#L72.
What we need here is restart_handler.

Thanks anyway :)

Alex

>
> >
> >
> > > +
> > >       return ret;
> > >   }
> > >
> > > diff --git a/include/linux/mfd/da9063/core.h b/include/linux/mfd/da9063/core.h
> > > index fa7a43f02f27..1b20c498e340 100644
> > > --- a/include/linux/mfd/da9063/core.h
> > > +++ b/include/linux/mfd/da9063/core.h
> > > @@ -85,6 +85,9 @@ struct da9063 {
> > >       int             chip_irq;
> > >       unsigned int    irq_base;
> > >       struct regmap_irq_chip_data *regmap_irq;
> > > +
> > > +     /* Restart */
> > > +     struct notifier_block restart_handler;
> > >   };
> > >
> > >   int da9063_device_init(struct da9063 *da9063, unsigned int irq);
> >
> > Note, the watchdog driver for the DA9063 also has a restart method
> > although it also does not set the AUTOBOOT bit either.
> >
> > The best thing is to enable the watchdog driver, the SiFive release
> > does not have either the core DA9063 or the watchdog driver for it
> > enabled.
>
> It seems that for the restart implemented here to work, the AUTOBOOT
> bit needs to be set in the OTP, which seems not to be the case with
> the chip on this board: it's been discussed here
> https://www.dialog-semiconductor.com/products/pmics?post_id=10052#tab-support_tab_content
> (see the accepted answer).
>
> Thanks,
>
> Alex
>
> >
> > --
> > Ben Dooks                               http://www.codethink.co.uk/
> > Senior Engineer                         Codethink - Providing Genius
> >
> > https://www.codethink.co.uk/privacy.html