On Thu, 19 Sep 2019 at 09:40, Suniel Mahesh <sunil.m@xxxxxxxxxxxx> 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
