[PATCHv2 2/5] watchdog: add support for adjusting last known HW keepalive time

[Tero Kristo]

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>
---
 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
+ *	immediately. This adjusts the watchdog ping period to match
+ *	the currently running timer.
+ */
+int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
+				   unsigned int last_ping_ms)
+{
+	struct watchdog_core_data *wd_data = wdd->wd_data;
+	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 *);
 
-- 
2.17.1

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