On Fri, Feb 07, 2014 at 10:44:53AM -0500, Jason Cooper wrote: > On Fri, Feb 07, 2014 at 12:17:28PM -0300, Ezequiel Garcia wrote: > > On Fri, Feb 07, 2014 at 05:38:09AM -0800, Guenter Roeck wrote: > > > On 02/07/2014 02:40 AM, Ezequiel Garcia wrote: > > > > On Thu, Feb 06, 2014 at 06:02:56PM -0800, Guenter Roeck wrote: > > > >> On 02/06/2014 09:20 AM, Ezequiel Garcia wrote: > > > >>> Having the watchdog initially fully stopped is important to avoid > > > >>> any spurious watchdog triggers, in case the registers are not in > > > >>> its reset state. > > > >>> > > > >>> Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx> > > > >>> Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@xxxxxxxxx> > > > >>> Tested-by: Willy Tarreau <w@xxxxxx> > > > >>> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@xxxxxxxxxxxxxxxxxx> > > > >>> --- > > > >>> drivers/watchdog/orion_wdt.c | 3 +++ > > > >>> 1 file changed, 3 insertions(+) > > > >>> > > > >>> diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c > > > >>> index 6746033..2dbeee9 100644 > > > >>> --- a/drivers/watchdog/orion_wdt.c > > > >>> +++ b/drivers/watchdog/orion_wdt.c > > > >>> @@ -142,6 +142,9 @@ static int orion_wdt_probe(struct platform_device *pdev) > > > >>> orion_wdt.max_timeout = wdt_max_duration; > > > >>> watchdog_init_timeout(&orion_wdt, heartbeat, &pdev->dev); > > > >>> > > > >>> + /* Let's make sure the watchdog is fully stopped */ > > > >>> + orion_wdt_stop(&orion_wdt); > > > >>> + > > > >> > > > >> Actually we just had that in another driver, and I stumbled over it there. > > > >> > > > >> Problem with stopping the watchdog in probe unconditionally is that you can > > > >> use it to defeat nowayout: unload the module, then load it again, > > > >> and the watchdog is stopped even if nowayout is true. > > > >> > > How often would a user legitimately want to unload/load the watchdog > module? > Not sure what you are saying here. If you don't think the nowayout option should be supported, drop it. Don't claim it is supported when it isn't. > > > > > > > > Hm... I see. > > > > > > > >> Is this really what you want ? Or, in other words, what is the problem > > > >> you are trying to solve ? > > > >> > > > > > > > > Well, this is related to the discussion about the bootloader not > > > > reseting the watchdog properly, provoking spurious watchdog triggering. > > > > > > > > Jason Gunthorpe explained [1] that we needed a particular sequence: > > > > > > > > 1. Disable WDT > > > > 2. Clear bridge > > > > 3. Enable WDT > > > > > > > > We added the irq handling to satisfy (2), and the watchdog stop for (1). > > > > > > > > The watchdog stop was agreed specifically [2]. > > > > > > > > Ideas? > > > > > > > > > > Other drivers assume that if the watchdog is running, it is supposed > > > to be running. The more common approach in such cases is to ping the > > > watchdog once to give userspace more time to get ready, but leave > > > it enabled. So you could check if the watchdog is enabled, and if > > > it was enabled re-enable it after initialization is complete > > > (and maybe log a message stating that the watchdog is enabled). > > > > > > If you don't want to do that, and if you are defeating nowayout > > > on purpose to fix a problem with a broken bootloader, > > > you should at least put in comment describing the problem you are > > > trying to solve, and that you accept breaking nowayout with your fix. > > Yes, this should be commented. > > > I'm not fond of not having "nowayout" option on our driver, given I'm sure > > it's a watchdog feature for a good reason. > > > > On the other side, I can't see how can we distinguish a previously > > and explicitly enabled watchdog, from a spurious enable by broken bootloader. > > How about we just don't define module_exit() and leave a comment as > such? It's not unprecedented, a couple of the atm drivers are > explicitly setup like this (uPD98402.c, zatm.c, eni.c). > Or don't support tristate in the first place. There was some argument from others earlier that a watchdog should never be optional. Or drop the nowayout option from the driver. There is one problem, though, if you don't support a pre-enabled watchdog: If the system dies before the watchdog application starts running, it will hang. This is the reason why the watchdog is enabled on purpose by some boot loaders. Guenter -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
