On Fri, Dec 05, 2014 at 08:42:07PM +0200, Timo Kokkonen wrote: > On 05.12.2014 16:12, Boris Brezillon wrote: > >Hi Timo, > > > >On Fri, 05 Dec 2014 14:57:05 +0200 > >Timo Kokkonen <timo.kokkonen@xxxxxxxxxx> wrote: > > > >>On 27.11.2014 21:00, Boris Brezillon wrote: > >>>Hi Timo, > >>> > >>>Sorry for the late reply. > >>> > >>>On Fri, 21 Nov 2014 14:23:30 +0200 > >>>Timo Kokkonen <timo.kokkonen@xxxxxxxxxx> wrote: > >>> > >>>>By default the driver will start a kernel timer which keeps on kicking > >>>>the watchdog HW until user space has opened the watchdog > >>>>device. Usually this is desirable as the watchdog HW is running by > >>>>default and the user space may not have any watchdog daemon running at > >>>>all. > >>>> > >>>>However, on production systems it may be mandatory that also early > >>>>crashes and lockups will lead to a watchdog reset, even if they happen > >>>>before the user space has opened the watchdog device. > >>>> > >>>>To resolve the issue, add a new device tree property > >>>>"enable-early-reset" which will prevent the kernel timer from pinging > >>>>the watchdog HW on behalf of user space. The default is still to use > >>>>kernel timer, but more strict behavior can be enabled via the device > >>>>tree property. > >>>> > >>>>Signed-off-by: Timo Kokkonen <timo.kokkonen@xxxxxxxxxx> > >>>>--- > >>>> Documentation/devicetree/bindings/watchdog/atmel-wdt.txt | 4 ++++ > >>>> drivers/watchdog/at91sam9_wdt.c | 6 +++++- > >>>> 2 files changed, 9 insertions(+), 1 deletion(-) > >>>> > >>>>diff --git a/Documentation/devicetree/bindings/watchdog/atmel-wdt.txt b/Documentation/devicetree/bindings/watchdog/atmel-wdt.txt > >>>>index f90e294..a0b7b75 100644 > >>>>--- a/Documentation/devicetree/bindings/watchdog/atmel-wdt.txt > >>>>+++ b/Documentation/devicetree/bindings/watchdog/atmel-wdt.txt > >>>>@@ -28,6 +28,10 @@ Optional properties: > >>>> entering idle state. > >>>> - atmel,dbg-halt : Should be present if you want to stop the watchdog when > >>>> entering debug state. > >>>>+- enable-early-reset : Should be present if you want to let the > >>>>+ watchdog timer to expire even before user space has opened the > >>>>+ device. If not set, a kernel timer will keep on pinging the > >>>>+ watchdog until it is opened. > >>> > >>>If you want to make this property generic, maybe you should document it > >>>in a generic binding doc > >>>(Documentation/devicetree/bindings/watchdog/watchdog.txt ?). > >>>Once you're at it, maybe you could document the generic timeout-sec > >>>property in this file. > >>>Moreover, you might want to parse this property in watchdog_core.c and > >>>store the information in the watchdog_device struct. > >> > >>I gave a little thought about this today and we could maybe have it like > >>watchdog_init_timeout() is today. But I can't really think of any > >>generic handling for this property, anything else except storing the > >>parsed value to a variable in watchdog_device struct. Everything else is > >>HW specific, except how we read the variable.. If we had some logic or > >>checking for this variable (other than to check it is not negative) > >>maybe then it would make sense. > > > >Okay, I'm fine with keeping this DT property parsing out of the core. > > Ok, good. > > >> > >>So I could write a patch to document generic watchdog properties in > >>Documentation/devicetree/bindings/watchdog/watchdog.txt (anything else > >>generic that would go there except timeout-sec and enable-early-reset?) > > > >I'm not sure you and Guenter agreed on the 'early-keepalive-sec' > >property (and this one won't be used in atmel driver since you can't > >change the timeout once set), so I'd say the timeout-sec and > >enable-early-reset are the only common properties for now. > > Actually it can be done in Atmel driver as well. It already has a > timer that keeps on pinging the watchdog until user space opens it. > We just modify the code so that it keeps on pinging the watchdog > until early-keepalive-sec has expired. No need to change the HW > timeouts at all. And I rather have it implemented that way anyway, > the 16 second timeout is a little tight if there happens to be a lot > of stuff already in the early user space. > > Yeah, I didn't get anything back from Guenter about my > early-keepalive-sec property proposal. Frankly, I already forgot > about it my self already. I guess I'll get back to you with v3 set > once I get time for it. Probably easiest to continue from there. > Sorry for that, folks. I have been a bit overwhelmed in the last cycle. early-timeout-sec seems to be the best property name to me right now. It is aligned with the existing timeout-sec. early-keepalive-sec seems kind of different just for the purpose of being different. Not sure about how to name enable-early-reset. I'd prefer to have something generic, even if only implemented in a single driver for now, but I don't really know right now what that might/should look like. Maybe just "enable-early" to indicate that the watchdog should be enabled during init ? Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
