linux-kernel - Re: R: [PATCH v1] watchdog: wdat: add param. to start wdog on module insertion

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Message-ID: <4ed7ec8c-d5bf-41b8-96c4-b34db670315d@roeck-us.net>
Date:   Fri, 19 Feb 2021 07:32:59 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Flavio Suligoi <f.suligoi@...m.it>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: R: [PATCH v1] watchdog: wdat: add param. to start wdog on module
 insertion

On 2/19/21 6:01 AM, Flavio Suligoi wrote:
> Hi Mika,
> 
>>>  	 const struct wdat_instruction *instr, u32 *value)
>>>  {
>>> @@ -437,6 +443,8 @@ static int wdat_wdt_probe(struct platform_device
>> *pdev)
>>>  	}
>>>
>>>  	wdat_wdt_boot_status(wdat);
>>> +	if (start_enabled)
>>> +		wdat_wdt_start(&wdat->wdd);
>>
>> No objections to this if it is really needed. However, I think it is
>> better start the watchdog after devm_watchdog_register_device() has been
>> called so we have everything initialized.
> 
> Yes, it is needed. We need this feature to enable the watchdog
> as soon as possible and this is essential for unmanned applications,
> such as routers, water pumping stations, climate data collections,
> etc.  
> 
FWIW, in your use case the watchdog should be enabled in the
BIOS/ROMMON.

> Right, ok for the correct positioning of the wdat_wdt_start function
> at the end of the watchdog device initialization. Thanks!
> 

No, it isn't, because it won't set WDOG_HW_RUNNING, and the
watchdog core won't know that the watchdog is running.
The watchdog has to be started before the call to
wdat_wdt_set_running(). If that isn't possible with the
current location of wdat_wdt_set_running(), then
wdat_wdt_set_running() has to be moved accordingly.
Either case, both have to be called before calling
devm_watchdog_register_device().

Having said that, I'd prefer to have a module parameter
in the watchdog core. We already have a number of similar
module parameters in various drivers, all named differently,
and I'd rather not have more.

Guenter

>>
>>>  	wdat_wdt_set_running(wdat);
>>>
>>>  	ret = wdat_wdt_enable_reboot(wdat);
>>> --
>>> 2.25.1
> 
> Regards,
> Flavio
>