Re: [PATCH v3 1/2] dt-bindings: can: m_can: add out-band-wakeup property

[Conor Dooley <conor@kernel.org>]

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On Fri, Aug 28, 2026 at 11:07:29AM +0200, Krzysztof Kozlowski wrote:
> On Mon, Aug 24, 2026 at 05:50:20PM +0100, Conor Dooley wrote:
> > On Fri, Aug 21, 2026 at 02:05:11PM -0500, Kendall Willis wrote:
> > > On 17:45-20260821, Conor Dooley wrote:
> > > > On Fri, Aug 21, 2026 at 11:07:00AM -0500, Kendall Willis wrote:
> > > > > Add the out-band-wakeup property as a possible property. The property
> > > > > indicates that the device can wakeup the system even when its power
> > > > > domain is off.
> > > > > 
> > > > > Signed-off-by: Kendall Willis <k-willis@ti.com>
> > > > > ---
> > > > >  Documentation/devicetree/bindings/net/can/bosch,m_can.yaml | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml b/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
> > > > > index 2c9d37975bedd652b3060ab11ba75c37565edaad..0663beaa532bcc4a71cd6ad01520a4dfea294d0c 100644
> > > > > --- a/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
> > > > > +++ b/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
> > > > > @@ -150,6 +150,8 @@ properties:
> > > > >      description:
> > > > >        List of phandles to system idle states in which mcan can wakeup the system.
> > > > >  
> > > > > +  out-band-wakeup: true
> > > > 
> > > > Where is "-wakeup" defined genericly, or out-band-wakeup defined that
> > > > you're getting the property definition from?
> > > 
> > > I sent a PR to define out-band-wakeup in the wakeup-source.yaml binding
> > > in dt-schema repo. I figured it made more sense to be defined in the
> > > wakeup-source.yaml binding to allow other drivers the option to use it.
> > > 
> > > dt-schema PR:
> > > https://github.com/devicetree-org/dt-schema/pull/205
> > 
> > This sounds like something you should be able to determine from
> > device specific compatibles for these platforms. Not sure why they are
> > not used for this particular device, but this is an indication to me
> > that that is a mistake.
> 
> Yeah, it looks a bit too much replicating Linux PM detail. I can imagine
> that some devices on some board are capable of waking up the system even
> when power domain is off, but this does not look like a capability of
> the actual device, but power domain. Device does not have different
> wakeups. (by device I mean this individual schema - Bosch CAN)
> 
> Happy to see some bigger picture through DTS or board layouts. Actually
> DTS, showing same Bosch CAN devices which are different on a board -
> some are wakeups and some out of band wakeups - would illustrate it
> better.

As far as I could make out when I looked at the patch, "Bosch CAN" is an
IP that can be integrated on an SoC rather than a device on the board,
so I'm doubting that there's any difference in capability to wake up the
device caused by the board at all. If there is, it's between different
power domains on the SoC, as you say.

> 
> Best regards,
> Krzysztof
> 

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