Re: [PATCH v2 1/6] wdt: sunxi: Move restart code to the watchdog driver

[Guenter Roeck]

On 06/23/2014 02:30 PM, Wim Van Sebroeck wrote:
> Hi All,
>
> > On Mon, Jun 23, 2014 at 07:30:56AM -0700, Guenter Roeck wrote:
> > > > > The patches _are_ in my watchdog-next branch and get some coverage from
> > > > > both my auto-builders and from Fenguang's build robots, so while they are
> > > > > not in linux-next, they are not completely in the dark either.
> > > >
> > > > So, this patch finally didn't make it into 3.16. Great. Now, we can't
> > > > even reboot the boards.
> > > >
> > > > Given how it's just impossible to get something merged reliably
> > > > through the watchdog tree, I guess I should just start merging the
> > > > patches through mine?
> > >
> > > You can not really blame Wim here.
> > >
> > > In this case, I suspect the major reason for not accepting the patch
> > > is that I tried to provide a clean method / API for "reset through watchdog
> > > subsystem", which went nowhere, in my understanding because someone objected
> > > that it would be the wrong thing to do [1] and it didn't get approval /
> > > acceptance from the arm maintainers. If it is wrong to reset the board
> > > from the watchdog subsystem in a clean way, it is for sure even more wrong
> > > to do it as you proposed in your patch.
> > >
> > > My conclusion therefore is that all board reset code should move back out
> > > of the watchdog subsystem, and that we should not accept such code in the
> > > future. This is not my personal preference, but I do believe that we should
> > > do it in a clean way or not at all.
> >
> > Well, considering that this patch isn't depending on your reboot API
> > set, and that Wim never either commented on this patch, your reboot
> > API patchset or your pull request to say that he was not willing to
> > merge this, there's still a huge failure to communicate.
> >
> > I'm fine with any technical reason, let's debate on that. But the
> > point is there has been no debate at all, only silence from his side.
> >
> > I have been told some patches would be merged and I merged through my
> > tree some patches that were depending on this one based on that
> > assumption.
> >
> > And now, we have a regression.
> >
> > Anyway... I guess I should just revert some commits now.
>
> To continue the discussion: I would like to add an excerpt from drivers/watchdog/alim7101_wdt.c
> /*
>   *      Notifier for system down
>   */
>
> static int wdt_notify_sys(struct notifier_block *this,
>                                          unsigned long code, void *unused)
> {
>          if (code == SYS_DOWN || code == SYS_HALT)
>                  wdt_turnoff();
>
>          if (code == SYS_RESTART) {
>                  /*
>                   * Cobalt devices have no way of rebooting themselves other
>                   * than getting the watchdog to pull reset, so we restart the
>                   * watchdog on reboot with no heartbeat
>                   */
>                  wdt_change(WDT_ENABLE);
>                  pr_info("Watchdog timer is now enabled with no heartbeat - should reboot in ~1 second\n");
>          }
>          return NOTIFY_DONE;
> }
>
> For some systems the watchdog is the only way to reboot... So where we should put it, is not trivial neither...

Agreed. The above definitely doesn't look like a good solution to me.

Guenter

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