linux-kernel - Re: [PATCH] watchdog: max77620: Add support for watchdog timer

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Message-ID: <57581A7F.4000200@roeck-us.net>
Date:	Wed, 8 Jun 2016 06:15:43 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	wim@...ana.be, linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org
Subject: Re: [PATCH] watchdog: max77620: Add support for watchdog timer

On 06/08/2016 01:58 AM, Laxman Dewangan wrote:
> Hi Guenter,
>
> Thanks for quick review. I will take care of most of comment.
> I have one query fr following comment.
>
> Thanks,
> Laxman
>
> On Tuesday 07 June 2016 11:26 PM, Guenter Roeck wrote:
>> Hi,
>>
>> On Mon, Jun 06, 2016 at 05:22:44PM +0530, Laxman Dewangan wrote:
>> +    /* Stop watchodog */
>> +    ret = regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL2,
>> +                 MAX77620_WDTEN, 0);
>> +    if (ret < 0) {
>> +        dev_err(wdt->dev, "Failed to reset WDTEN: %d\n", ret);
>> +        return ret;
>> +    }
>> Alternatively, you could set WDOG_HW_RUNNING to tell the watchdog core
>> that the watchdog is already running. The watchdog core would then ping
>> the watchdog until the watchdog device is opened.
>>
>> That would also require to tell the watchdog core about the current (or default)
>> timeout, which doesn't seem to be set anywhere. That means it won't be set at all
>> unless user space updates it explicitly. This is quite unusual. Is it on purpose
>> or an oversight ? If it is on purpose, please explain.
>
> OK, we have use cases where we have enabled the WDT in BL also. and keep runnign till kernel up.
> Instead of stopping WDT, I can say that WDOG_HW_RUNING and current timeout can be read from the register.
>
> Now, the WDT need to be ping periodically. Is there any flag which enabled the worker thread from core which will keep pinging till user space alive and activate the WDT?
>
The watchdog core will start the worker if WDOG_HW_RUNNING is set.

Guenter