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

Marc Zyngier
2020-02-07T11:09:53Z

On 2020-02-07 11:00, Peng Fan wrote:
>> 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?

Or rather just a function ID, full stop. the conduit *MUST* be inherited
from the PSCI context.

M.
--
Jazz is not dead. It just smells funny...