Hi Timo,
On Wed, 18 Feb 2015 14:57:22 +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
> "early-timeout-sec" which will let the kernel timer to ping the
> watchdog HW only as long as the specified timeout permits. 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/watchdog.txt | 7 +++++++
> drivers/watchdog/at91sam9_wdt.c | 9 ++++++++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/watchdog/watchdog.txt b/Documentation/devicetree/bindings/watchdog/watchdog.txt
> index 7e3686c..32647cf 100644
> --- a/Documentation/devicetree/bindings/watchdog/watchdog.txt
> +++ b/Documentation/devicetree/bindings/watchdog/watchdog.txt
> @@ -4,9 +4,16 @@ using these definitions.
>
> Optional properties:
> - timeout-sec: Contains the watchdog timeout in seconds.
> +- early-timeout-sec: If present, specifies a timeout value in seconds
> + that the driver keeps on ticking the watchdog HW on behalf of user
> + space. Once this timeout expires watchdog is left to expire in
> + timeout-sec seconds. If this propery is set to zero, watchdog is
> + started (or left running) so that a reset occurs in timeout-sec
> + since the watchdog was started.
>
> Example:
>
> watchdog {
> timeout-sec = <60>;
> + early-timeout-sec = <120>;
> };
IMHO the documentation update should be self-contained (it should be
done in a separate patch).
Best Regards,
Boris
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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