watchdog: aspeed: add nowayout support

Add support for not stopping the watchdog
when the userspace application quits. At
closing of the device, the driver cannot
determine if this was a graceful closure
or if the app crashed. If the support
of nowayout on this driver, the system integrator
can select the behaviour by setting the kernel
config and enabling it.

Cc: Wim Van Sebroeck <wim@linux-watchdog.org> (maintainer:WATCHDOG DEVICE DRIVERS)
Cc: Guenter Roeck <linux@roeck-us.net> (maintainer:WATCHDOG DEVICE DRIVERS)
Cc: Joel Stanley <joel@jms.id.au> (supporter:ARM/ASPEED MACHINE SUPPORT)
Cc: Andrew Jeffery <andrew@aj.id.au> (reviewer:ARM/ASPEED MACHINE SUPPORT)
Cc: linux-watchdog@vger.kernel.org (open list:WATCHDOG DEVICE DRIVERS)
Cc: linux-arm-kernel@lists.infradead.org (moderated list:ARM/ASPEED MACHINE SUPPORT)
Cc: linux-aspeed@lists.ozlabs.org (moderated list:ARM/ASPEED MACHINE SUPPORT)
Cc: linux-kernel@vger.kernel.org (open list)
Signed-off-by: Eduardo Valentin <eduval@amazon.com>
Signed-off-by: Eduardo Valentin <evalenti@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220212021033.2344-1-eduval@amazon.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/aspeed_wdt.c

@@ -13,6 +13,11 @@
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>
 
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
 struct aspeed_wdt {
 	struct watchdog_device	wdd;
 	void __iomem		*base;
@@ -266,6 +271,8 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
 	wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
 	watchdog_init_timeout(&wdt->wdd, 0, dev);
 
+	watchdog_set_nowayout(&wdt->wdd, nowayout);
+
 	np = dev->of_node;
 
 	ofdid = of_match_node(aspeed_wdt_of_table, np);