watchdog: Improve description of min_hw_heartbeat_ms

The description of min_hw_heartbeat_ms is misleading and needs some
improvements.
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/watchdog-kernel-api.txt

@@ -82,8 +82,9 @@ 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.
+* min_hw_heartbeat_ms: Hardware limit for minimum time between heartbeats,
+  in milli-seconds. This value is normally 0; it should only be provided
+  if the hardware can not tolerate lower intervals between heartbeats.
 * 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

include/linux/watchdog.h

@@ -66,7 +66,8 @@ struct watchdog_ops {
  *		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.
+ *		Hardware limit for minimum time between heartbeats,
+ *		in milli-seconds.
  * @max_hw_heartbeat_ms:
  *		Hardware limit for maximum timeout, in milli-seconds.
  *		Replaces max_timeout if specified.