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    Subject[PATCH v6 4/9] 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>

    ---
    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 | 4 ++++
    drivers/watchdog/watchdog_dev.c | 12 ++++++++++++
    include/linux/watchdog.h | 6 ++++++
    3 files changed, 22 insertions(+)

    diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
    index f2ee8226d320..b417fdb6caac 100644
    --- a/Documentation/watchdog/watchdog-kernel-api.txt
    +++ b/Documentation/watchdog/watchdog-kernel-api.txt
    @@ -53,11 +53,13 @@ struct watchdog_device {
    unsigned int timeout;
    unsigned int min_timeout;
    unsigned int max_timeout;
    + unsigned int min_hw_heartbeat_ms;
    unsigned int max_hw_timeout_ms;
    void *driver_data;
    unsigned long status;
    struct mutex lock;
    unsigned long last_keepalive;
    + unsigned long last_hw_keepalive;
    struct delayed_work work;
    struct list_head deferred;
    };
    @@ -83,6 +85,8 @@ 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_timeout_ms is non-zero.
    +* min_hw_heartbeat_ms: Minimum time between heartbeats sent to the chip,
    + in milli-seconds.
    * max_hw_timeout_ms: Maximum hardware timeout, in milli-seconds.
    If set, the infrastructure will send heartbeats to the watchdog driver
    if 'timeout' is larger than max_hw_timeout, unless WDOG_ACTIVE
    diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
    index 5dd7319c0169..82706d43e0c8 100644
    --- a/drivers/watchdog/watchdog_dev.c
    +++ b/drivers/watchdog/watchdog_dev.c
    @@ -111,6 +111,8 @@ static inline void watchdog_update_worker(struct watchdog_device *wdd,

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

    if (test_bit(WDOG_UNREGISTERED, &wdd->status))
    @@ -119,6 +121,13 @@ static int _watchdog_ping(struct watchdog_device *wdd)
    if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
    return 0;

    + if (time_is_after_jiffies(earliest_keepalive)) {
    + mod_delayed_work(watchdog_wq, &wdd->work,
    + earliest_keepalive - jiffies);
    + return 0;
    + }
    +
    + wdd->last_hw_keepalive = jiffies;
    if (wdd->ops->ping)
    err = wdd->ops->ping(wdd); /* ping the watchdog */
    else
    @@ -667,6 +676,9 @@ int watchdog_dev_register(struct watchdog_device *wdd)
    return err;
    }

    + /* Record time of most recent heartbeat as 'just before now'. */
    + wdd->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 98f79db93600..606dfd55927f 100644
    --- a/include/linux/watchdog.h
    +++ b/include/linux/watchdog.h
    @@ -66,6 +66,8 @@ struct watchdog_ops {
    * @max_timeout:The watchdog devices maximum timeout value (in seconds)
    * as configurable from user space. Only relevant if
    * max_hw_timeout_ms is not provided.
    + * @min_hw_heartbeat_ms:
    + * Minimum time between heartbeats, in milli-seconds.
    * @max_hw_timeout_ms:
    * Hardware limit for maximum timeout, in milli-seconds.
    * Replaces max_timeout if specified.
    @@ -75,6 +77,8 @@ struct watchdog_ops {
    * @last_keepalive:
    * Time of most recent keepalive triggered from user space,
    * in jiffies (watchdog core internal).
    + * @last_hw_keepalive:
    + * Time of most recent keepalive sent to the driver, in jiffies.
    * @work: Data structure for worker function (watchdog core internal).
    * @deferred: entry in wtd_deferred_reg_list which is used to
    * register early initialized watchdogs.
    @@ -99,6 +103,7 @@ struct watchdog_device {
    unsigned int timeout;
    unsigned int min_timeout;
    unsigned int max_timeout;
    + unsigned int min_hw_heartbeat_ms;
    unsigned int max_hw_timeout_ms;
    void *driver_data;
    unsigned long status;
    @@ -112,6 +117,7 @@ struct watchdog_device {
    /* the following variables are for internal use only */
    struct mutex lock;
    unsigned long last_keepalive;
    + unsigned long last_hw_keepalive;
    struct delayed_work work;
    struct list_head deferred;
    };
    --
    2.1.4


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