Re: [PATCH v2 1/1] watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend

Alexandre Belloni
2019-06-14T20:33:43Z

On 14/06/2019 18:43:22+0000, Ken Sloat wrote:
> Well I'm a little confused still because there are two separate comments
> in these statements. The first within resume implies that the init should
> be called because we might have lost register values for some reason
> unexplained.

The sama5d2 has a suspend mode where power to the core is completely
cut. Only a few IPs remain powered (in the backup power domain).
Unfortunately, the watchdog is not in that domain and may lose its
registers.

> Then within the init it says that the bootloader might have
> modified the registers so we should check them and then update it or
> otherwise disable it. I'm not trying to pick apart the logic or anything,
> I'm just readily assuming it is good as it was already reviewed before.
>

The bootloaders may have started the watchdog (this makes sense if you
really care about reliability) and so we need to be careful to keep the
proper parameters.

> So without digging into that too much, if we don't know if any of the runtime
> situations above might have occurred, then isn't it best to leave my patch
> as is? Yes this has the side effect of resetting the timer count, but if
> the init call is needed and we don't have any way to know if any
> of the situations occurred, then we have no choice right?
>

Until we can differentiate between suspend modes, we have no other
choice.

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering