Documentation: add sbsa-gwdt driver documentation

The sbsa-gwdt.txt documentation in devicetree/bindings/watchdog is for
introducing SBSA(Server Base System Architecture) Generic Watchdog
device node info into FDT.

Also add sbsa-gwdt introduction in watchdog-parameters.txt

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Fu Wei <fu.wei@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 31 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/watchdog/sbsa-gwdt.txt b/Documentation/devicetree/bindings/watchdog/sbsa-gwdt.txt
new file mode 100644
index 000000000000..6f2d5f91964d
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/sbsa-gwdt.txt
@@ -0,0 +1,31 @@
+* SBSA (Server Base System Architecture) Generic Watchdog
+
+The SBSA Generic Watchdog Timer is used to force a reset of the system
+after two stages of timeout have elapsed.  A detailed definition of the
+watchdog timer can be found in the ARM document: ARM-DEN-0029 - Server
+Base System Architecture (SBSA)
+
+Required properties:
+- compatible: Should at least contain "arm,sbsa-gwdt".
+
+- reg: Each entry specifies the base physical address of a register frame
+  and the length of that frame; currently, two frames must be defined,
+  in this order:
+  1: Watchdog control frame;
+  2: Refresh frame.
+
+- interrupts: Should contain the Watchdog Signal 0 (WS0) SPI (Shared
+  Peripheral Interrupt) number of SBSA Generic Watchdog.
+
+Optional properties
+- timeout-sec: Watchdog timeout values (in seconds).
+
+Example for FVP Foundation Model v8:
+
+watchdog@2a440000 {
+        compatible = "arm,sbsa-gwdt";
+        reg = <0x0 0x2a440000 0 0x1000>,
+              <0x0 0x2a450000 0 0x1000>;
+        interrupts = <0 27 4>;
+        timeout-sec = <30>;
+};