RE: [PATCH 1/2] dt-bindings: arm: arm,scmi: add smc/hvc transports

Peng Fan
2020-02-07T11:01:22Z

> Subject: Re: [PATCH 1/2] dt-bindings: arm: arm,scmi: add smc/hvc transports
>
> On 2020-02-07 10:47, Sudeep Holla wrote:
> > On Fri, Feb 07, 2020 at 10:08:36AM +0000, Marc Zyngier wrote:
> >> On 2020-02-06 13:01, peng.fan@nxp.com wrote:
> >> > From: Peng Fan <peng.fan@nxp.com>
> >> >
> >> > SCMI could use SMC/HVC as tranports, so add into devicetree binding
> >> > doc.
> >> >
> >> > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> >> > ---
> >> > Documentation/devicetree/bindings/arm/arm,scmi.txt | 4 +++-
> >> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt
> >> > b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> >> > index f493d69e6194..03cff8b55a93 100644
> >> > --- a/Documentation/devicetree/bindings/arm/arm,scmi.txt
> >> > +++ b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> >> > @@ -14,7 +14,7 @@ Required properties:
> >> >
> >> > The scmi node with the following properties shall be under the
> >> > /firmware/ node.
> >> >
> >> > -- compatible : shall be "arm,scmi"
> >> > +- compatible : shall be "arm,scmi" or "arm,scmi-smc"
> >> > - mboxes: List of phandle and mailbox channel specifiers. It
> >> > should contain
> >> > exactly one or two mailboxes, one for transmitting messages("tx")
> >> > and another optional for receiving the notifications("rx") if
> >> > @@ -25,6 +25,8 @@ The scmi node with the following properties shall
> >> > be under the /firmware/ node.
> >> > protocol identifier for a given sub-node.
> >> > - #size-cells : should be '0' as 'reg' property doesn't have any size
> >> > associated with it.
> >> > +- arm,smc-id : SMC id required when using smc transports
> >> > +- arm,hvc-id : HVC id required when using hvc transports
> >> >
> >> > Optional properties:
> >>
> >> Not directly related to DT: Why do we need to distinguish between SMC
> >> and HVC?
> >
> > IIUC you want just one property to get the function ID ? Does that
> > align with what you are saying ? I wanted to ask the same question and
> > I see no need for 2 different properties.
>
> Exactly. Using SMC or HVC should come from the context, and there is zero
> value in having different different IDs, depending on the conduit.
>
> We *really* want SMC and HVC to behave the same way. Any attempt to
> make them different should just be NAKed.

ok. Then just like psci node,
Add a "method" property for each protocol, and add "arm,func-id" to
indicate the ID.

How about this?

Thanks,
Peng.

>
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...