watchdog: add a driver to support SAMA5D4 watchdog timer

From SAMA5D4, the watchdog timer is upgrated with a new feature,
which is describled as in the datasheet, "WDT_MR can be written
until a LOCKMR command is issued in WDT_CR".
That is to say, as long as the bootstrap and u-boot don't issue
a LOCKMR command, WDT_MR can be written more than once in the driver.

So the SAMA5D4 watchdog driver's implementation is different from
the at91sam9260 watchdog driver implemented in file at91sam9_wdt.c.
The user application open the device file to enable the watchdog timer
hardware, and close to disable it, and set the watchdog timer timeout
by seting WDV and WDD fields of WDT_MR register, and ping the watchdog
by issuing WDRSTT command to WDT_CR register with hard-coded key.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index cd99fcce3bab..ce0658c92fe8 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -188,6 +188,15 @@ config AT91SAM9X_WATCHDOG
           Watchdog timer embedded into AT91SAM9X and AT91CAP9 chips. This will
           reboot your system when the timeout is reached.
 
+config SAMA5D4_WATCHDOG
+        tristate "Atmel SAMA5D4 Watchdog Timer"
+        depends on ARCH_AT91
+        select WATCHDOG_CORE
+        help
+          Atmel SAMA5D4 watchdog timer is embedded into SAMA5D4 chips.
+          Its Watchdog Timer Mode Register can be written more than once.
+          This will reboot your system when the timeout is reached.
+
 config CADENCE_WATCHDOG
         tristate "Cadence Watchdog Timer"
         depends on HAS_IOMEM