[U-Boot] [PATCH] watchdog/imx_watchdog: do not set WCR_WDW

[Stefano Babic]

Hi Sebastian,

On 25/03/2015 13:15, Sebastian Andrzej Siewior wrote:

>>
>> Just some questions. The described behavior is coherent with the
>> description in the manual. When WDW is set, the watchdog is stopped
>> while the processor is in wait mode.
> 
> I fail to notice how it could make any sense.

Well, I have not said it makes sense - only that the behavior is
expected ;-)

> 
>> Current imx2_wdt.c driver in kernel does not care about this bit, but it
>> looks like that only the kernel and/or the application can decide if the
>> watchdog should run when the system is in WAIT or not. The bootloader
>> cannot decide, and it should set the bit for its own usage.
>>
>> Should this setup be done by the kernel driver instead of by the
>> bootloader ?
> 
> It is a one-time-bit. Once it is set (or not) it can not be changed
> later. It makes no difference for the bootloader.

mmhhh..Sorry, it looks like I read the wrong line in the manual. This is
a write once bit exactly as WDZST. My assumption were wrong. We cannot
disable in kernel if the bootloader has already activated it.

> And the kernel may
> remain idle for longer than one jiffy with NO_HZ but it will still wake
> up within a second if I remember correctly. Eitherway the user will
> usually trigger the WD in timeout/2 so atleast that timer will wake up
> the kernel from idle.
> Having the WDT not account the idle time makes it hard for the user to
> figure out how much time has been accounted by the WDT so far.

I have no objections here - I start from the wrong assumption that the
bit could be cleared by the kernel, but it is not.

> 
>>>
>>> While I don't see a reason why the WDT should not be running while the
>>> CPU is in idle, I'm dropping this bit.
>>
>> I can agree or disagree. This depends on the application.
>>
>> Differently as the WDZST, that can be set only once, and it is set by
>> *both* U-Boot and kernel (setting in kernel has then no influence), the
>> WDW can be even disabled in kernel.
> 
> I patched the kernel as well. Once I get through here I would also push
> patches there. The thing I don't like is that the kernel pings the WDT
> on its own. While it may make sense for some people I would like to
> atleast configure it :)

Agree, patch put in my merge queue.

Acked-by: Stefano Babic <sbabic at denx.de>

Best regards,
Stefano

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