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From:   Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
To:     Alexandre Ghiti <alexandre.ghiti@canonical.com>,
        Support Opensource <Support.Opensource@diasemi.com>,
        Lee Jones <lee.jones@linaro.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] drivers: mfd: da9063: Add restart notifier implementation
Thread-Topic: [PATCH] drivers: mfd: da9063: Add restart notifier
 implementation
Thread-Index: AQHXrqpI0LoFC+MHc0+B+6k9QHIUIauzTVsw
Date:   Fri, 24 Sep 2021 15:04:00 +0000
Message-ID: <DB9PR10MB465252461469340F60A8714780A49@DB9PR10MB4652.EURPRD10.PROD.OUTLOOK.COM>
References: <20210921053356.1705833-1-alexandre.ghiti@canonical.com>
In-Reply-To: <20210921053356.1705833-1-alexandre.ghiti@canonical.com>
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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.
>=20
> The original implementation comes from Marcus Comstedt and Anders
> Montonen
> (https://forums.sifive.com/t/reboot-command/4721/28).
>=20
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
> ---
>  drivers/mfd/da9063-core.c       | 25 +++++++++++++++++++++++++
>  include/linux/mfd/da9063/core.h |  3 +++
>  2 files changed, 28 insertions(+)
>=20
> 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>
>=20
>  #include <linux/mfd/da9063/core.h>
>  #include <linux/mfd/da9063/registers.h>
> @@ -158,6 +159,18 @@ static int da9063_clear_fault_log(struct da9063 *da9=
063)
>  	return ret;
>  }
>=20
> +static int da9063_restart_notify(struct notifier_block *this,
> +				 unsigned long mode, void *cmd)
> +{
> +	struct da9063 *da9063 =3D 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 be=
lieve
we should have multiple of these.

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.