linux-kernel - Re: [PATCH v2 3/8] watchdog: JZ4740: Register a restart handler

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Date:   Sat, 20 Jan 2018 13:01:17 +0530
From:   PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Wim Van Sebroeck <wim@...ana.be>,
        Guenter Roeck <linux@...ck-us.net>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v2 3/8] watchdog: JZ4740: Register a restart handler

Hi Paul,

On 30 December 2017 at 19:21, Paul Cercueil <paul@...pouillou.net> wrote:
> The watchdog driver can restart the system by simply configuring the
> hardware for a timeout of 0 seconds.
>
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/watchdog/jz4740_wdt.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
>  v2: No change
>
> diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
> index 92d6ca8ceb49..fa7f49a3212c 100644
> --- a/drivers/watchdog/jz4740_wdt.c
> +++ b/drivers/watchdog/jz4740_wdt.c
> @@ -130,6 +130,14 @@ static int jz4740_wdt_stop(struct watchdog_device *wdt_dev)
>         return 0;
>  }
>
> +static int jz4740_wdt_restart(struct watchdog_device *wdt_dev,
> +                             unsigned long action, void *data)
> +{
> +       wdt_dev->timeout = 0;
> +       jz4740_wdt_start(wdt_dev);
> +       return 0;
> +}
> +
>  static const struct watchdog_info jz4740_wdt_info = {
>         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
>         .identity = "jz4740 Watchdog",
> @@ -141,6 +149,7 @@ static const struct watchdog_ops jz4740_wdt_ops = {
>         .stop = jz4740_wdt_stop,
>         .ping = jz4740_wdt_ping,
>         .set_timeout = jz4740_wdt_set_timeout,
> +       .restart = jz4740_wdt_restart,
>  };
>
>  #ifdef CONFIG_OF
> --
> 2.11.0
>
>

Noticed that min_timeout of the watchdog device is set to 1 but this
function calls start with timeout set to 0. Even though this works I
feel it is better to set min_timeout to 0.

Regards,
PrasannaKumar