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SubjectRe: [PATCHv2 2/5] watchdog: add support for adjusting last known HW keepalive time
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On 7/3/20 5:04 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@ti.com>
> ---
> drivers/watchdog/watchdog_dev.c | 23 +++++++++++++++++++++++
> include/linux/watchdog.h | 2 ++
> 2 files changed, 25 insertions(+)
>
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index bc1cfa288553..5848551cf29d 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -1138,6 +1138,29 @@ void watchdog_dev_unregister(struct watchdog_device *wdd)
> watchdog_cdev_unregister(wdd);
> }
>
> +/*
> + * watchdog_set_last_hw_keepalive: set last HW keepalive time for watchdog
> + *
> + * Adjusts the last known HW keepalive time for a watchdog timer.
> + * This is needed in case where watchdog has been started before
> + * kernel by someone like bootloader, and it can't be pinged

... needed if the watchdog is already running when the probe function
is called, and ...

> + * immediately. This adjusts the watchdog ping period to match
> + * the currently running timer.

It doesn't adjust the ping period.

> + */

last_ping_ms needs to be documented (the last heartbeat was last_ping_ms
milliseconds ago ?), both here and in Documentation/watchdog/watchdog-kernel-api.rst.
It needs to be documented that the function must be called immediately
after watchdog registration, and that min_hw_heartbeat_ms must
be set for it to be useful.

> +int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
> + unsigned int last_ping_ms)
> +{
> + struct watchdog_core_data *wd_data = wdd->wd_data;

This needs a NULL check, in case it is called before watchdog driver
registration.

> + ktime_t now;
> +
> + 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 *);
>
>

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