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

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Date:   Tue, 21 Sep 2021 15:46:49 +0530
From:   Anup Patel <anup@...infault.org>
To:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Cc:     Support Opensource <support.opensource@...semi.com>,
        Lee Jones <lee.jones@...aro.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: mfd: da9063: Add restart notifier implementation

On Tue, Sep 21, 2021 at 11:04 AM Alexandre Ghiti
<alexandre.ghiti@...onical.com> 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;
> +}
> +
>  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;

How was this priority value chosen ?

I mean, we will be having SBI SRST as well so we should choose
a priority value lower than what we choose for SBI SRST handler.

Regards,
Anup

> +       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);
> +
>         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);
> --
> 2.30.2
>