Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO_SUSPEND

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 07/03/2015 at 11:39:39 +0100, Pavel Machek wrote :
> > The Atmel watchdog can't be stopped once it's started. This is actually 
> > very useful so we can reset if suspend or resume failed, the only 
> > drawback is that you have to wake up from time to time (e.g. by using 
> > the RTC/RTT) to clear the watchdog and then go back to sleep ASAP.
> 
> Yeah. So you do "echo mem > /sys/power/state", and few seconds/minutes
> after watchdog kills the system. But you did not ask for dead system,
> you asked for suspend.
> 
> And while that behaviour is useful for you, I don't think it is
> exactly useful behaviour, nor it is the behaviour user would expect.
> 

I think you misunderstood, that is exactly the expected behaviour. This
is hardware defined. Once the watchdog is started, nobody can stop it.
Trying to change the mode register will result in a reset of the SoC.

It is documented in the datasheet and any user wanting another behaviour
is out of luck.

So basically, when using a watchdog, you have to wake up every 15-16s to
restart it.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux PPP]     [Linux FS]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Linmodem]     [Device Mapper]     [Linux Kernel for ARM]

  Powered by Linux