On 7/17/20 6:29 AM, Tero Kristo wrote:
> Certain watchdogs require the watchdog only to be pinged within a
> specific time window, pinging too early or too late cause the watchdog
> to fire. In cases where this sort of watchdog has been started before
> kernel comes up, we must adjust the watchdog keepalive window to match
> the actually running timer, so add a new driver API for this purpose.
>
> Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> .../watchdog/watchdog-kernel-api.rst | 12 ++++++++
> drivers/watchdog/watchdog_dev.c | 30 +++++++++++++++++++
> include/linux/watchdog.h | 2 ++
> 3 files changed, 44 insertions(+)
>
> diff --git a/Documentation/watchdog/watchdog-kernel-api.rst b/Documentation/watchdog/watchdog-kernel-api.rst
> index 068a55ee0d4a..baf44e986b07 100644
> --- a/Documentation/watchdog/watchdog-kernel-api.rst
> +++ b/Documentation/watchdog/watchdog-kernel-api.rst
> @@ -336,3 +336,15 @@ an action is taken by a preconfigured pretimeout governor preassigned to
> the watchdog device. If watchdog pretimeout governor framework is not
> enabled, watchdog_notify_pretimeout() prints a notification message to
> the kernel log buffer.
> +
> +To set the last known HW keepalive time for a watchdog, the following function
> +should be used::
> +
> + int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
> + unsigned int last_ping_ms)
> +
> +This function must be called immediately after watchdog registration. It
> +sets the last known hardware heartbeat to have happened last_ping_ms before
> +current time. Calling this is only needed if the watchdog is already running
> +when probe is called, and the watchdog can only be pinged after the
> +min_hw_heartbeat_ms time has passed from the last ping.
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index bc1cfa288553..e74a0c6811b5 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -1138,6 +1138,36 @@ void watchdog_dev_unregister(struct watchdog_device *wdd)
> watchdog_cdev_unregister(wdd);
> }
>
> +/*
> + * watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
> + * @wdd: watchdog device
> + * @last_ping_ms: time since last HW heartbeat
> + *
> + * Adjusts the last known HW keepalive time for a watchdog timer.
> + * This is needed if the watchdog is already running when the probe
> + * function is called, and it can't be pinged immediately. This
> + * function must be called immediately after watchdog registration,
> + * and min_hw_heartbeat_ms must be set for this to be useful.
> + */
> +int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
> + unsigned int last_ping_ms)
> +{
> + struct watchdog_core_data *wd_data;
> + ktime_t now;
> +
> + if (!wdd)
> + return -EINVAL;
> +
> + wd_data = wdd->wd_data;
> +
> + now = ktime_get();
> +
> + wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
> +
> + return __watchdog_ping(wdd);
> +}
> +EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
> +
> /*
> * watchdog_dev_init: init dev part of watchdog core
> *
> diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
> index 1464ce6ffa31..9b19e6bb68b5 100644
> --- a/include/linux/watchdog.h
> +++ b/include/linux/watchdog.h
> @@ -210,6 +210,8 @@ extern int watchdog_init_timeout(struct watchdog_device *wdd,
> extern int watchdog_register_device(struct watchdog_device *);
> extern void watchdog_unregister_device(struct watchdog_device *);
>
> +int watchdog_set_last_hw_keepalive(struct watchdog_device *, unsigned int);
> +
> /* devres register variant */
> int devm_watchdog_register_device(struct device *dev, struct watchdog_device *);
>
>
