Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support

[Guenter Roeck]

On 02/05/2016 10:21 AM, Fu Wei wrote:
> On 5 February 2016 at 22:42, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > On 02/05/2016 01:51 AM, Fu Wei wrote:
> > > Hi Guenter,
> > >
> > > On 4 February 2016 at 13:17, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > > > On 02/03/2016 03:00 PM, Fu Wei wrote:
> > > > > On 4 February 2016 at 02:45, Timur Tabi <timur@xxxxxxxxxxxxxx> wrote:
> > > > > > Fu Wei wrote:
> > > > > > > As you know I have made the pre-timeout support patch, If people like
> > > > > > > it, i am happy to go on upstream it separately.
> > > > > > >
> > > > > > > If we want to use pre-timeout here, user only can use get_pretimeout
> > > > > > > and disable panic by setting pretimeout to 0
> > > > > > > but user can not really set pretimeout, because "pre-timeout  ==
> > > > > > > timeout / 2 (always)".
> > > > > > > if user want to change pretimeout, he/she has to set_time instead.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > Ok, I think patches 4 and 5 should be combined, and I think the Kconfig
> > > > > > entry should be removed and just use panic_enabled.
> > > >
> > > >
> > > >
> > > > Agreed.
> > >
> > >
> > > np, will do
> > >
> > > > > NP, will update this patchset like that ,  thanks :-)
> > > >
> > > > Also, if panic is enabled, the timeout needs to be adjusted accordingly
> > > > (to only panic after the entire timeout period has expired, not after
> > > > half of it). We can not panic the system after timeout / 2.
> > >
> > >
> > > OK, my thought is
> > >
> > > if panic is enabled :
> > > |--------WOR-------WS0--------WOR-------WS1
> > > |------timeout------(panic)------timeout-----reset
> > >
> > > if panic is disabled .
> > > |--------WOR-------WS0--------WOR-------WS1
> > > |---------------------timeout---------------------reset
> > >
> > >    panic_enabled only can be configured when module is loaded by module
> > > parameter
> > >
> > > But user should know that max_timeout(panic_enable) =
> > > max_timeout(panic_disable) / 2
> >
> > That means you'll have to update max_timeout accordingly.
>
> panic_enabled only can be configured when module is loaded, so we
> don't need to update it.
>
> max_timeout will only be set up in the init stage.
>
> Does it make sense ? :-)
Not sure I understand your problem or question.

max_timeout will have to reflect the correct maximum timeout, under
all circumstances. It will have to be set to the correct value before
the watchdog driver is registered.

Guenter