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

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Message-ID: <CA+zEjCvKaS0sE7paCecMDvqpkw-yLM_QFHdF5pgWTAqeH0JAfA@mail.gmail.com>
Date:   Fri, 24 Sep 2021 18:17:19 +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,

On Fri, Sep 24, 2021 at 5:04 PM Adam Thomson
<Adam.Thomson.Opensource@...semi.com> wrote:
>
> On 21 September 2021 06:34, 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@...onical.com>
> > ---
> >  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;
> > +}
>
> 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 :)

Thanks,

Alex

>
> For board specific sequences, there are machine quirks I believe which can be
> used to handle stuff like this, if this really isn't a generic solution to fit
> all cases.
>