> On Feb 18, 2015, at 8:57 PM, 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 ++++++++-
This should not be handled by the driver but the kernel in a generic way
Best Regards,
J.
> 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>;
> };
> diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
> index 6df9405..1b40bfa 100644
> --- a/drivers/watchdog/at91sam9_wdt.c
> +++ b/drivers/watchdog/at91sam9_wdt.c
> @@ -89,6 +89,8 @@ struct at91wdt {
> u32 mr_mask;
> unsigned long heartbeat; /* WDT heartbeat in jiffies */
> bool nowayout;
> + /* Timeout in jiffies for stopping the early timer */
> + unsigned long early_timer;
> unsigned int irq;
> };
>
> @@ -122,7 +124,8 @@ static void at91_ping(unsigned long data)
> {
> struct at91wdt *wdt = (struct at91wdt *)data;
> if (time_before(jiffies, wdt->next_heartbeat) ||
> - !watchdog_active(&wdt->wdd)) {
> + (time_before(jiffies, wdt->early_timer) &&
> + !watchdog_active(&wdt->wdd))) {
> at91_wdt_reset(wdt);
> mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
> } else {
> @@ -316,6 +319,10 @@ static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
>
> wdt->mr |= max | ((max - min) << 16);
>
> + if (!of_property_read_u32_index(np, "early-timeout-sec", 0,
> + (u32 *)&wdt->early_timer))
> + wdt->early_timer = wdt->early_timer * HZ + jiffies;
> +
> return 0;
> }
> #else
> --
> 2.1.0
>
>
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