linux-kernel - Re: [PATCH v3] rtc: ds1307: provide an indication that the watchdog has fired

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Message-ID: <20e6115f-f0dd-6e37-ae16-9f409ac4c413@roeck-us.net>
Date:   Mon, 27 Jul 2020 06:32:47 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        a.zummo@...ertech.it, alexandre.belloni@...tlin.com
Cc:     linux-rtc@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rtc: ds1307: provide an indication that the watchdog
 has fired

On 7/26/20 8:46 PM, Chris Packham wrote:
> There's not much feedback when the ds1388 watchdog fires. Generally it
> yanks on the reset line and the board reboots. Capture the fact that the
> watchdog has fired in the past so that userspace can retrieve it via
> WDIOC_GETBOOTSTATUS. This should help distinguish a watchdog triggered
> reset from a power interruption.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
> Changes in v3:
> - Check for watchdog flag in ds1307_wdt_register()
> Changes in v2:
> - Set bootstatus to WDIOF_CARDRESET and let userspace decide what to do with
>   the information.
> 
>  drivers/rtc/rtc-ds1307.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 49702942bb08..54c85cdd019d 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -1668,6 +1668,8 @@ static const struct watchdog_ops ds1388_wdt_ops = {
>  static void ds1307_wdt_register(struct ds1307 *ds1307)
>  {
>  	struct watchdog_device	*wdt;
> +	int err;
> +	int val;
>  
>  	if (ds1307->type != ds_1388)
>  		return;
> @@ -1676,6 +1678,10 @@ static void ds1307_wdt_register(struct ds1307 *ds1307)
>  	if (!wdt)
>  		return;
>  
> +	err = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &val);
> +	if (!err && val & DS1388_BIT_WF)
> +		wdt->bootstatus = WDIOF_CARDRESET;
> +
>  	wdt->info = &ds1388_wdt_info;
>  	wdt->ops = &ds1388_wdt_ops;
>  	wdt->timeout = 99;
>