mpc52xx/wdt: OF property to enable the WDT on boot
PATCH v2 1/3 mpc52xx/wdt: OF property to enable the WDT on boot
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.
---
Change against v1: rename the new property.
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | 17 ++++++++++++++++- 1 files changed, 16 insertions(+), 1 deletions(-)
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt +16 -1
@@ -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:
Quoted 27 lines · Albrecht Dreß
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 <[email protected]>---
Change against v1: rename the new property.
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt | 17 ++++++++++++++++-
1 files changed, 16 insertions(+), 1 deletions(-)Documentation/powerpc/dts-bindings/fsl/mpc5200.txt +0
-0@@ -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 shouldDocumentation/powerpc/dts-bindings/fsl/mpc5200.txt +6
-1-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. +
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt fsl,mpc5200-gpt nodes · line 121
Quoted 10 lines
Documentation/powerpc/dts-bindings/fsl/mpc5200.txt +10
-0+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.
Signature · 2 lines
Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.
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Hi Grant!
Am 12.11.09 20:06 schrieb(en) Grant Likely:
Quoted 4 lines
Quoted 1 line
+The watchdog will respect the
CONFIG_WATCHDOG_NOWAYOUToption.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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