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References: <20200924074715.GT9675@piout.net> <20200924105256.18162-1-u.kleine-koenig@pengutronix.de>
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From:   Bruno Thomsen <bruno.thomsen@gmail.com>
Date:   Sun, 27 Sep 2020 10:09:50 +0200
Message-ID: <CAH+2xPAVvMpTgT3W=0AsKy=9jkS8qd6eB65Qebw51YKRQshaGQ@mail.gmail.com>
Subject: Re: [PATCH 2/2] [RFC] rtc: pcf2127: only use watchdog when explicitly available
To:     =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>
Cc:     Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Qiang Zhao <qiang.zhao@nxp.com>, linux-rtc@vger.kernel.org,
        Alessandro Zummo <a.zummo@towertech.it>,
        linux-watchdog@vger.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Sascha Hauer <kernel@pengutronix.de>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Guenter Roeck <linux@roeck-us.net>
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Den tor. 24. sep. 2020 kl. 12.53 skrev Uwe Kleine-K=C3=B6nig
<u.kleine-koenig@pengutronix.de>:
>
> Most boards using the pcf2127 chip (in my bubble) don't make use of the
> watchdog functionality and the respective output is not connected. The
> effect on such a board is that there is a watchdog device provided that
> doesn't work.
>
> So only register the watchdog if the device tree has a "has-watchdog"
> property.
>
> Signed-off-by: Uwe Kleine-K=C3=B6nig <u.kleine-koenig@pengutronix.de>
> ---
>  drivers/rtc/rtc-pcf2127.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> index 5b1f1949b5e5..8bd89d641578 100644
> --- a/drivers/rtc/rtc-pcf2127.c
> +++ b/drivers/rtc/rtc-pcf2127.c
> @@ -340,7 +340,8 @@ static int pcf2127_watchdog_init(struct device *dev, =
struct pcf2127 *pcf2127)
>         u32 wdd_timeout;
>         int ret;
>
> -       if (!IS_ENABLED(CONFIG_WATCHDOG))
> +       if (!IS_ENABLED(CONFIG_WATCHDOG) ||
> +           !device_property_read_bool(dev, "has-watchdog"))
>                 return 0;

I don't think the compiler can remove the function if
CONFIG_WATCHDOG is disabled due to the device tree
value check. Maybe it can if split into 2 conditions.

if (!IS_ENABLED(CONFIG_WATCHDOG))
        return 0;
if (!device_property_read_bool(dev, "has-watchdog"))
        return 0;

/Bruno

>
>         pcf2127->wdd.parent =3D dev;
> --
> 2.28.0
>