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

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Date:   Fri, 7 Feb 2020 11:00:37 +0000
From:   Peng Fan <peng.fan@....com>
To:     Marc Zyngier <maz@...nel.org>, Sudeep Holla <sudeep.holla@....com>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "andre.przywara@....com" <andre.przywara@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 1/2] dt-bindings: arm: arm,scmi: add smc/hvc transports

> 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@....com wrote:
> >> > From: Peng Fan <peng.fan@....com>
> >> >
> >> > SCMI could use SMC/HVC as tranports, so add into devicetree binding
> >> > doc.
> >> >
> >> > Signed-off-by: Peng Fan <peng.fan@....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...