watchdog: honour hw_margin_ms DT property

Some watchdog devices, e.g. external gpio-triggered ones, must be
reset more often than once per second, which means that the current
rate-limiting logic in watchdog_reset() fails to keep the board alive.

gpio-wdt.txt in the linux source tree defines a "hw_margin_ms"
property used to specifiy the maximum time allowed between resetting
the device. Allow any watchdog device to specify such a property, and
then use a reset period of one quarter of that. We keep the current
default of resetting once every 1000ms.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/drivers/watchdog/wdt-uclass.c b/drivers/watchdog/wdt-uclass.c
index c96a596f08c124788bec01f25cbdebb1ffb9265b..4cdb7bd64cdf4267628fb869e244a7f5df245d19 100644 (file)
--- a/drivers/watchdog/wdt-uclass.c
+++ b/drivers/watchdog/wdt-uclass.c
@@ -16,6 +16,12 @@ DECLARE_GLOBAL_DATA_PTR;
 
 #define WATCHDOG_TIMEOUT_SECS  (CONFIG_WATCHDOG_TIMEOUT_MSECS / 1000)
 
+/*
+ * Reset every 1000ms, or however often is required as indicated by a
+ * hw_margin_ms property.
+ */
+static ulong reset_period = 1000;
+
 int initr_watchdog(void)
 {
        u32 timeout = WATCHDOG_TIMEOUT_SECS;
@@ -37,6 +43,9 @@ int initr_watchdog(void)
        if (CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)) {
                timeout = dev_read_u32_default(gd->watchdog_dev, "timeout-sec",
                                               WATCHDOG_TIMEOUT_SECS);
+               reset_period = dev_read_u32_default(gd->watchdog_dev,
+                                                   "hw_margin_ms",
+                                                   4 * reset_period) / 4;
        }
 
        wdt_start(gd->watchdog_dev, timeout * 1000, 0);
@@ -118,7 +127,7 @@ void watchdog_reset(void)
        /* Do not reset the watchdog too often */
        now = get_timer(0);
        if (time_after(now, next_reset)) {
-               next_reset = now + 1000;        /* reset every 1000ms */
+               next_reset = now + reset_period;
                wdt_reset(gd->watchdog_dev);
        }
 }