* [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
@ 2009-11-12 18:43 ` Albrecht Dreß
0 siblings, 0 replies; 6+ messages in thread
From: Albrecht Dreß @ 2009-11-12 18:43 UTC (permalink / raw)
To: Likely, Grant, Linux PPC Development, Devicetree Discussions,
Wim Van Sebroeck
Add the "fsl,wdt-on-boot" OF property as to reserve a GPT as WDT which may
be a requirement in safety-related (e.g. ISO/EN 61508) applications.
Signed-off-by: Albrecht Dreß <albrecht.dress@arcor.de>
---
Change against v1: rename the new property.
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | 17 ++++++++++++++++-
1 files changed, 16 insertions(+), 1 deletions(-)
diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
index 8447fd7..ddd5ee3 100644
--- a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
+++ b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
@@ -103,7 +103,22 @@ 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
+ fsl,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.
+
+The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
An mpc5200-gpt can be used as a single line GPIO controller. To do so,
add the following properties to the gpt node:
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
@ 2009-11-12 18:43 ` Albrecht Dreß
0 siblings, 0 replies; 6+ messages in thread
From: Albrecht Dreß @ 2009-11-12 18:43 UTC (permalink / raw)
To: Likely, Grant, Linux PPC Development, Devicetree Discussions,
Wim Van Sebroeck
Add the "fsl,wdt-on-boot" OF property as to reserve a GPT as WDT which may
be a requirement in safety-related (e.g. ISO/EN 61508) applications.
Signed-off-by: Albrecht Dre=DF <albrecht.dress@arcor.de>
---
Change against v1: rename the new property.
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | 17 ++++++++++++++++=
-
1 files changed, 16 insertions(+), 1 deletions(-)
diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documenta=
tion/powerpc/dts-bindings/fsl/mpc5200.txt
index 8447fd7..ddd5ee3 100644
--- a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
+++ b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
@@ -103,7 +103,22 @@ 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
+ fsl,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.
+
+The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
=20
An mpc5200-gpt can be used as a single line GPIO controller. To do so,
add the following properties to the gpt node:
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
2009-11-12 18:43 ` Albrecht Dreß
@ 2009-11-12 19:06 ` Grant Likely
-1 siblings, 0 replies; 6+ messages in thread
From: Grant Likely @ 2009-11-12 19:06 UTC (permalink / raw)
To: Albrecht Dreß
Cc: Linux PPC Development, Devicetree Discussions, Wim Van Sebroeck
On Thu, Nov 12, 2009 at 11:43 AM, Albrecht Dreß <albrecht.dress@arcor.de> wrote:
> Add the "fsl,wdt-on-boot" OF property as to reserve a GPT as WDT which may
> be a requirement in safety-related (e.g. ISO/EN 61508) applications.
>
> Signed-off-by: Albrecht Dreß <albrecht.dress@arcor.de>
>
> ---
>
> Change against v1: rename the new property.
>
> Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | 17 ++++++++++++++++-
> 1 files changed, 16 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
> index 8447fd7..ddd5ee3 100644
> --- a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
> +++ b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
> @@ -103,7 +103,22 @@ 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
> + fsl,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.
> +
> +The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
I think it would be better to use a device tree property to enable up
NOWAYOUT. The static config isn't multiplatform-friendly. Thoughts?
Otherwise, this looks good to me.
g.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
@ 2009-11-12 19:06 ` Grant Likely
0 siblings, 0 replies; 6+ messages in thread
From: Grant Likely @ 2009-11-12 19:06 UTC (permalink / raw)
To: Albrecht Dreß
Cc: Linux PPC Development, Devicetree Discussions, Wim Van Sebroeck
On Thu, Nov 12, 2009 at 11:43 AM, Albrecht Dre=DF <albrecht.dress@arcor.de>=
wrote:
> Add the "fsl,wdt-on-boot" OF property as to reserve a GPT as WDT which ma=
y
> be a requirement in safety-related (e.g. ISO/EN 61508) applications.
>
> Signed-off-by: Albrecht Dre=DF <albrecht.dress@arcor.de>
>
> ---
>
> Change against v1: rename the new property.
>
> =A0Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | =A0 17 ++++++++++=
++++++-
> =A01 files changed, 16 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt b/Documen=
tation/powerpc/dts-bindings/fsl/mpc5200.txt
> index 8447fd7..ddd5ee3 100644
> --- a/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
> +++ b/Documentation/powerpc/dts-bindings/fsl/mpc5200.txt
> @@ -103,7 +103,22 @@ 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 fsl,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.
> +
> +The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
I think it would be better to use a device tree property to enable up
NOWAYOUT. The static config isn't multiplatform-friendly. Thoughts?
Otherwise, this looks good to me.
g.
--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
2009-11-12 19:06 ` Grant Likely
@ 2009-11-12 20:33 ` Albrecht Dreß
-1 siblings, 0 replies; 6+ messages in thread
From: Albrecht Dreß @ 2009-11-12 20:33 UTC (permalink / raw)
To: Grant Likely
Cc: Linux PPC Development, Devicetree Discussions, Wim Van Sebroeck
[-- Attachment #1.1: Type: text/plain, Size: 1032 bytes --]
Hi Grant!
Am 12.11.09 20:06 schrieb(en) Grant Likely:
> > +The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
>
> I think it would be better to use a device tree property to enable up
> NOWAYOUT. The static config isn't multiplatform-friendly. Thoughts?
I fully agree with you that this property would fit perfectly in the device tree. However, if we now add it *only* for the 52xx, but not for other device tree-aware platforms, this might be somewhat confusing. The good thing is that it wouldn't break
anything for the 5200 as the old wdt driver didn't work anyway.
One *real* advantage of the compile-time option is that it actually removes the code which stops the wdt. I'm not a real expert in that, but if we argue that the system is "safe" as required by IEC/EN 61508 part 3, it's probably beneficial if we can show
that there *is* no code to stop the wdt, not a snipplet only disabled by a flag.
Just my €0.01, though - maybe more insight from the WDT gurus?
Cheers, Albrecht.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot
@ 2009-11-12 20:33 ` Albrecht Dreß
0 siblings, 0 replies; 6+ messages in thread
From: Albrecht Dreß @ 2009-11-12 20:33 UTC (permalink / raw)
To: Grant Likely
Cc: Linux PPC Development, Devicetree Discussions, Wim Van Sebroeck
[-- Attachment #1: Type: text/plain, Size: 1032 bytes --]
Hi Grant!
Am 12.11.09 20:06 schrieb(en) Grant Likely:
> > +The watchdog will respect the CONFIG_WATCHDOG_NOWAYOUT option.
>
> I think it would be better to use a device tree property to enable up
> NOWAYOUT. The static config isn't multiplatform-friendly. Thoughts?
I fully agree with you that this property would fit perfectly in the device tree. However, if we now add it *only* for the 52xx, but not for other device tree-aware platforms, this might be somewhat confusing. The good thing is that it wouldn't break
anything for the 5200 as the old wdt driver didn't work anyway.
One *real* advantage of the compile-time option is that it actually removes the code which stops the wdt. I'm not a real expert in that, but if we argue that the system is "safe" as required by IEC/EN 61508 part 3, it's probably beneficial if we can show
that there *is* no code to stop the wdt, not a snipplet only disabled by a flag.
Just my €0.01, though - maybe more insight from the WDT gurus?
Cheers, Albrecht.
[-- Attachment #2: Type: application/pgp-signature, Size: 190 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
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2009-11-12 18:43 [PATCHv2 1/3] mpc52xx/wdt: OF property to enable the WDT on boot Albrecht Dreß
2009-11-12 18:43 ` Albrecht Dreß
2009-11-12 19:06 ` Grant Likely
2009-11-12 19:06 ` Grant Likely
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2009-11-12 20:33 ` Albrecht Dreß
2009-11-12 20:33 ` Albrecht Dreß
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