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

[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 Dre=DF <albrecht.dress@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/Documenta=
tion/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 boar=
d
 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 activat=
e
+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, an=
y
+gpt api call to this timer will fail with -EBUSY.
+
+If you add the property
+	wdt,on-boot =3D <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=3D0, th=
e
+configuration of the watchdog is not touched.  This is useful in two cases=
:
+- just mark GPT0 as watchdog, blocking gpt accesses, and configure it late=
r;
+- do not touch a configuration assigned by the boot loader which supervise=
s
+  the boot process itself.
=20
 An mpc5200-gpt can be used as a single line GPIO controller.  To do so,
 add the following properties to the gpt node:

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

[Grant Likely]

On Tue, Nov 10, 2009 at 12:40 PM, Albrecht Dre=DF <albrecht.dress@arcor.de>=
 wrote:
> 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 Dre=DF <albrecht.dress@arcor.de>
> ---
>
> =A0Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | =A0 15 ++++++++++=
++++-
> =A01 files changed, 14 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documen=
tation/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
> =A0---------------------
> =A0On the mpc5200 and 5200b, GPT0 has a watchdog timer function. =A0If th=
e board
> =A0design 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'. =A0Note that this does not act=
ivate
> +the watchdog. =A0The timer will function as a GPT if the timer api is us=
ed, and
> +it will function as watchdog if the watchdog device is used. =A0The watc=
hdog
> +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
> + =A0 =A0 =A0 wdt,on-boot =3D <n>;
> +GPT0 will be marked as in-use watchdog, i.e. blocking every gpt access t=
o it.
> +If n>0, the watchdog is started with a timeout of n seconds. =A0If n=3D0=
, the
> +configuration of the watchdog is not touched. =A0This is useful in two c=
ases:
> +- just mark GPT0 as watchdog, blocking gpt accesses, and configure it la=
ter;
> +- do not touch a configuration assigned by the boot loader which supervi=
ses
> + =A0the boot process itself.

I'm not *totally* convinced on the usage model, but I just need some
time to think about it.  Give me a day or so and ping me again if you
haven't heard from me.  However, until a common WDT binding is
defined, this property needs to be named something like
"fsl,wdt-on-boot".

Cheers,
g.

--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.