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

[Guenter Roeck]

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.

> > I am not too happy with the parameter name (panic_enabled). How about
> > "action", to match machzwd ?
>
> yes, makes sense. Maybe we can do something  like this:
>
> /*
>   * action refers to action taken when watchdog gets WS0
>   * 0 = SKIP
>   * 1 = PANIC
>   * defaults to SKIP (0)
>   */
> static int action;
> module_param(action, int, 0);
> MODULE_PARM_DESC(action, "after watchdog gets WS0 interrupt, do: "
> "0 = SKIP(*)  1 = PANIC");
Yes, though I would suggest to use lower case letters.

Thanks,
Guenter