[PATCH 1/3] mpc52xx/wdt: OF property to enable the WDT on boot

[Albrecht Dreß]

Add the "wdt,on-boot" OF property as to reserve a GPT as WDT which may be a
requirement in safety-related (e.g. ISO 61508) applications.

Signed-off-by: Albrecht Dreß <albrecht.dress at arcor.de>
---

 Documentation/powerpc/dts-bindings/fsl/mpc5200.txt |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
index 8447fd7..1eecb06 100644
--- a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
+++ b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
@@ -103,7 +103,20 @@ fsl,mpc5200-gpt nodes
 ---------------------
 On the mpc5200 and 5200b, GPT0 has a watchdog timer function.  If the board
 design supports the internal wdt, then the device node for GPT0 should
-include the empty property 'fsl,has-wdt'.
+include the empty property 'fsl,has-wdt'.  Note that this does not activate
+the watchdog.  The timer will function as a GPT if the timer api is used, and
+it will function as watchdog if the watchdog device is used.  The watchdog
+mode has priority over the gpt mode, i.e. if the watchdog is activated, any
+gpt api call to this timer will fail with -EBUSY.
+
+If you add the property
+	wdt,on-boot = <n>;
+GPT0 will be marked as in-use watchdog, i.e. blocking every gpt access to it.
+If n>0, the watchdog is started with a timeout of n seconds.  If n=0, the
+configuration of the watchdog is not touched.  This is useful in two cases:
+- just mark GPT0 as watchdog, blocking gpt accesses, and configure it later;
+- do not touch a configuration assigned by the boot loader which supervises
+  the boot process itself.
 
 An mpc5200-gpt can be used as a single line GPIO controller.  To do so,
 add the following properties to the gpt node: