From mboxrd@z Thu Jan 1 00:00:00 1970 From: timo.kokkonen@offcode.fi (Timo Kokkonen) Date: Fri, 28 Nov 2014 08:42:57 +0200 Subject: [PATCH] at91sam9_wdt: Allow watchdog to reset device at early boot In-Reply-To: <20141127200036.2c65df62@bbrezillon> References: <5465C00E.4030808@offcode.fi> <1416572610-1770-1-git-send-email-timo.kokkonen@offcode.fi> <20141127200036.2c65df62@bbrezillon> Message-ID: <54781971.4060600@offcode.fi> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Boris, Thanks for the comments. 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 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 >> --- >> 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. Yeah, I can take a look at it. Thanks, -Timo > Apart from that, I'm not opposed to the approach, and I'm fine with the > current implementation. > > Regards, > > Boris >