Subject: [PATCH] at91sam9_wdt: Allow watchdog to reset device at early boot

From: [email-masked] (Timo Kokkonen)
Date: Thu, 27 Nov 2014 08:53:51 +0200

Hi,

On 21.11.2014 14:23, 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 <[email-masked]>

I forgot to put the PATCHv2 on the subject line.. But anyway, any 
thoughts about it? Is there something that should be done to get it forward?

Thanks,
-Timo

> ---
>   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.
>
>   Example:
>   	watchdog at fffffd40 {
> diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
> index 489729b..78b1977 100644
> --- a/drivers/watchdog/at91sam9_wdt.c
> +++ b/drivers/watchdog/at91sam9_wdt.c
> @@ -89,6 +89,7 @@ struct at91wdt {
>   	u32 mr_mask;
>   	unsigned long heartbeat;	/* WDT heartbeat in jiffies */
>   	bool nowayout;
> +	bool no_early_timer;
>   	unsigned int irq;
>   };
>
> @@ -122,7 +123,7 @@ static void at91_ping(unsigned long data)
>   {
>   	struct at91wdt *wdt = (struct at91wdt *)data;
>   	if (time_before(jiffies, wdt->next_heartbeat) ||
> -	    !watchdog_active(&wdt->wdd)) {
> +		(!watchdog_active(&wdt->wdd) && !wdt->no_early_timer)) {
>   		at91_wdt_reset(wdt);
>   		mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
>   	} else {
> @@ -316,6 +317,9 @@ static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
>
>   	wdt->mr |= max | ((max - min) << 16);
>
> +	if (of_property_read_bool(np, "enable-early-reset"))
> +		wdt->no_early_timer = 1;
> +
>   	return 0;
>   }
>   #else
>