[PATCH 1/1] sysreset: watchdog: watchdog cannot power off

[François Ozog]

Hi Heinrich,

Le jeu. 4 nov. 2021 à 12:45, Heinrich Schuchardt <
heinrich.schuchardt at canonical.com> a écrit :

> On 11/4/21 10:55, François Ozog wrote:
> > Hi Heinrich,
> >
> > On Thu, 4 Nov 2021 at 10:31, Heinrich Schuchardt
> > <heinrich.schuchardt at canonical.com
> > <mailto:heinrich.schuchardt at canonical.com>> wrote:
> >
> >     The watchdog system reset driver can reboot the device but it cannot
> >     power
> >     it off. If power off is requested, the driver should not reset the
> >     system
> >     but leave powering off to one of the other system reset drivers.
> >
> >     As power cycling is typically not a feature of a watchdog driver the
> >     reset
> >     types SYSRESET_POWER and SYSRESET_POWER_OFF shall both be excluded.
> >
> > A candid question here. I know that IPMI can powercycle a platform.
> > How would we handle that should there be a way to make the power cycle
> > happen?
> > (for instance we could define a PSCI extension of SYSTEM_RESET2 to have
> > a power cycle effect)
>
> Your comment seems not to relate to the validity of the current patch.
>
yes. It was a related question to understand more about the topic.

>
> For PSCI we have a separate sysreset driver
> drivers/sysreset/sysreset_psci.c. That driver currently does not support
> SYSRESET_POWER.
>
> Once such an extension is offered by PSCI you should define a
> device-tree node property for it in Linux'
> Documentation/devicetree/bindings/arm/psci.yaml. Next implement a probe
> function in the driver code to detect that property. In
> psci_sysreset_request(), if type=SYSRESET_POWER, call the appropriate
> PSCI method if the extension is enabled or return -ENOSYS if the
> extension is not available.
>
> Currently in U-Boot I see no code invoking a reset with SYSRESET_POWER.
> You would have to change function do_reset() in
> drivers/sysreset/sysreset-uclass.c to accept a new argument to select
> this reset type.
>
> Best regards
>
> Heinrich
>
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François-Frédéric Ozog | *Director Business Development*
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