From: Krzysztof Kozlowski <krzk@kernel.org>
To: Suniel Mahesh <sunil.m@techveda.org>
Cc: kgene@kernel.org, wim@linux-watchdog.org, linux@roeck-us.net,
heiko@sntech.de,
"linux-samsung-soc@vger.kernel.org"
<linux-samsung-soc@vger.kernel.org>,
linux-watchdog@vger.kernel.org
Subject: Re: Samsung based S3C2440A chipset - watchdog timer issue
Date: Thu, 19 Sep 2019 10:38:16 +0200 [thread overview]
Message-ID: <CAJKOXPdoYZTr_4ysVxN17bo8FZzQXRJS=ch4BAZzY+bLsLhS9Q@mail.gmail.com> (raw)
In-Reply-To: <652bf0b2-3681-47f2-3b50-40edff52a7b5@techveda.org>
On Thu, 19 Sep 2019 at 09:40, Suniel Mahesh <sunil.m@techveda.org> wrote:
>
> Hi,
>
> I am working on one of the Samsung based S3C2440A chipset based target .
>
> I have couple of questions and I request someone to shed some light on these: (Thank you)
>
> The watchdog driver in linux, looks like, it just configured WDT but didn't start it (code snippet included below).
>
> May i know the reasson why WDT is not started ? Is it because u-boot already started WDT, implies it is not required to do the
> same once we jump into linux ? or is there any specific reason ?
>
> drivers/watchdog/s3c2410_wdt.c (line 53 and lines 616 - 625)
>
> #define S3C2410_WATCHDOG_ATBOOT (0)
> ....
> static int tmr_atboot = S3C2410_WATCHDOG_ATBOOT;
> ...
> ...
> if (tmr_atboot && started == 0) {
> dev_info(dev, "starting watchdog timer\n");
> s3c2410wdt_start(&wdt->wdt_device);
> } else if (!tmr_atboot) {
> /* if we're not enabling the watchdog, then ensure it is
> * disabled if it has been left running from the bootloader
> * or other source */
>
> s3c2410wdt_stop(&wdt->wdt_device);
> }
> ...
> ...
>
> Tried to start WDT in linux by assigning value 1 to S3C2410_WATCHDOG_ATBOOT. The target resets.
>
> please comment.
I think watchdog should not start during boot before user-space is
brought up. Otherwise who will ping it? Usually watchdog is started by
opening the watchdog device by user-space. If you need it to be
running without user-space, there are special flags for this (see
WDOG_HW_RUNNING and others).
Best regards,
Krzysztof
next prev parent reply other threads:[~2019-09-19 8:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 7:40 Samsung based S3C2440A chipset - watchdog timer issue Suniel Mahesh
2019-09-19 8:38 ` Krzysztof Kozlowski [this message]
2019-09-19 13:26 ` Guenter Roeck
2019-09-19 13:21 ` Guenter Roeck
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