watchdog: da9063_wdt: don't trigger watchdog too fast

Triggering the watchdog faster than T_WDMIN=256ms leads to resets of the
DA9063 chip. The datasheet says that the watchdog must only be triggered
in the timeframe T_WDMIN to T_WDMAX. The T_WDMAX is configured in the
driver.
Signed-off-by: Stefan Christ <s.christ@phytec.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/da9063_wdt.c

@@ -34,6 +34,7 @@ static const unsigned int wdt_timeout[] = { 0, 2, 4, 8, 16, 32, 65, 131 };
 #define DA9063_WDT_MIN_TIMEOUT		wdt_timeout[DA9063_TWDSCALE_MIN]
 #define DA9063_WDT_MAX_TIMEOUT		wdt_timeout[DA9063_TWDSCALE_MAX]
 #define DA9063_WDG_TIMEOUT		wdt_timeout[3]
+#define DA9063_RESET_PROTECTION_MS	256
 
 struct da9063_watchdog {
 	struct da9063 *da9063;
@@ -171,6 +172,7 @@ static int da9063_wdt_probe(struct platform_device *pdev)
 	wdt->wdtdev.ops = &da9063_watchdog_ops;
 	wdt->wdtdev.min_timeout = DA9063_WDT_MIN_TIMEOUT;
 	wdt->wdtdev.max_timeout = DA9063_WDT_MAX_TIMEOUT;
+	wdt->wdtdev.min_hw_heartbeat_ms = DA9063_RESET_PROTECTION_MS;
 	wdt->wdtdev.timeout = DA9063_WDG_TIMEOUT;
 	wdt->wdtdev.parent = &pdev->dev;