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    Subject[PATCH v8 05/10] watchdog: Add support for minimum time between heartbeats
    Date
    Some watchdogs require a minimum time between heartbeats.
    Examples are the watchdogs in DA9062 and AT91SAM9x.

    Signed-off-by: Guenter Roeck <linux@roeck-us.net>

    ---
    v8: Rebased to v4.5-rc5
    v7: Rebased to v4.5-rc1
    v6: Rebased to v4.4-rc2
    v5: Rebased to v4.4-rc1
    Fixed typo in documentation.
    v4: Added patch
    ---
    Documentation/watchdog/watchdog-kernel-api.txt | 3 +++
    drivers/watchdog/watchdog_dev.c | 15 +++++++++++++++
    include/linux/watchdog.h | 3 +++
    3 files changed, 21 insertions(+)

    diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
    index 9eabca1d9355..917eeeabfa5e 100644
    --- a/Documentation/watchdog/watchdog-kernel-api.txt
    +++ b/Documentation/watchdog/watchdog-kernel-api.txt
    @@ -52,6 +52,7 @@ struct watchdog_device {
    unsigned int timeout;
    unsigned int min_timeout;
    unsigned int max_timeout;
    + unsigned int min_hw_heartbeat_ms;
    unsigned int max_hw_heartbeat_ms;
    struct notifier_block reboot_nb;
    struct notifier_block restart_nb;
    @@ -81,6 +82,8 @@ It contains following fields:
    * max_timeout: the watchdog timer's maximum timeout value (in seconds),
    as seen from userspace. If set, the maximum configurable value for
    'timeout'. Not used if max_hw_heartbeat_ms is non-zero.
    +* min_hw_heartbeat_ms: Minimum time between heartbeats sent to the chip,
    + in milli-seconds.
    * max_hw_heartbeat_ms: Maximum hardware heartbeat, in milli-seconds.
    If set, the infrastructure will send heartbeats to the watchdog driver
    if 'timeout' is larger than max_hw_heartbeat_ms, unless WDOG_ACTIVE
    diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
    index 5163c3eb3428..2d6110278eac 100644
    --- a/drivers/watchdog/watchdog_dev.c
    +++ b/drivers/watchdog/watchdog_dev.c
    @@ -64,6 +64,7 @@ struct watchdog_core_data {
    struct watchdog_device *wdd;
    struct mutex lock;
    unsigned long last_keepalive;
    + unsigned long last_hw_keepalive;
    struct delayed_work work;
    unsigned long status; /* Internal status bits */
    #define _WDOG_DEV_OPEN 0 /* Opened ? */
    @@ -137,8 +138,19 @@ static inline void watchdog_update_worker(struct watchdog_device *wdd)

    static int __watchdog_ping(struct watchdog_device *wdd)
    {
    + struct watchdog_core_data *wd_data = wdd->wd_data;
    + unsigned long earliest_keepalive = wd_data->last_hw_keepalive +
    + msecs_to_jiffies(wdd->min_hw_heartbeat_ms);
    int err;

    + if (time_is_after_jiffies(earliest_keepalive)) {
    + mod_delayed_work(watchdog_wq, &wd_data->work,
    + earliest_keepalive - jiffies);
    + return 0;
    + }
    +
    + wd_data->last_hw_keepalive = jiffies;
    +
    if (wdd->ops->ping)
    err = wdd->ops->ping(wdd); /* ping the watchdog */
    else
    @@ -819,6 +831,9 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
    return err;
    }

    + /* Record time of most recent heartbeat as 'just before now'. */
    + wd_data->last_hw_keepalive = jiffies - 1;
    +
    /*
    * If the watchdog is running, prevent its driver from being unloaded,
    * and schedule an immediate ping.
    diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
    index f46ae4a8b353..eddf6e29fec9 100644
    --- a/include/linux/watchdog.h
    +++ b/include/linux/watchdog.h
    @@ -65,6 +65,8 @@ struct watchdog_ops {
    * @max_timeout:The watchdog devices maximum timeout value (in seconds)
    * as configurable from user space. Only relevant if
    * max_hw_heartbeat_ms is not provided.
    + * @min_hw_heartbeat_ms:
    + * Minimum time between heartbeats, in milli-seconds.
    * @max_hw_heartbeat_ms:
    * Hardware limit for maximum timeout, in milli-seconds.
    * Replaces max_timeout if specified.
    @@ -95,6 +97,7 @@ struct watchdog_device {
    unsigned int timeout;
    unsigned int min_timeout;
    unsigned int max_timeout;
    + unsigned int min_hw_heartbeat_ms;
    unsigned int max_hw_heartbeat_ms;
    struct notifier_block reboot_nb;
    struct notifier_block restart_nb;
    --
    2.5.0
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