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From:   Etienne Carriere <etienne.carriere@linaro.org>
Date:   Tue, 1 Mar 2022 15:11:44 +0100
Message-ID: <CAN5uoS8QotrsoWYX3rCjxCKQFJNhFBXHc6JDYAn1rcX6N5mj4w@mail.gmail.com>
Subject: Re: [PATCH v8 1/2] dt-bindings: arm: Add OP-TEE transport for SCMI
To:     Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Sudeep Holla <sudeep.holla@arm.com>,
        Cristian Marussi <cristian.marussi@arm.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Pengutronix Kernel Team <kernel@pengutronix.de>
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Precedence: bulk

Hi sorry,

I sent the mail while i was still typing it...
Here is with the full answer.


On Tue, 1 Mar 2022 at 15:05, Etienne Carriere
<etienne.carriere@linaro.org> wrote:
>
> Hello Ahmad,
>
> On Mon, 28 Feb 2022 at 17:01, Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> >
> > Hello Etienne,
> >
> > On 28.10.21 16:00, Etienne Carriere wrote:
> > > Introduce compatible "linaro,scmi-optee" for SCMI transport channel
> > > based on an OP-TEE service invocation. The compatible mandates a
> > > channel ID defined with property "linaro,optee-channel-id".
> >
> > I just found this thread via the compatible in the STM32MP131 patch set:
> > https://lore.kernel.org/all/20220225133137.813919-1-gabriel.fernandez@foss.st.com/
> >
> > Linux doesn't care whether PSCI is provided by TF-A, OP-TEE or something
> > else, so there is just the arm,psci* compatible.
> >
> > What's different about SCMI that this is not possible? Why couldn't the
> > existing binding and driver be used to communicate with OP-TEE as secure
> > monitor as well?
>
> Compatible "linaro,scmi-optee" denote a alternate SCMI transport to
> those already in v5.16.

It is names scmi-optee because the interface exposed to access SCMI services is
based on TEE's interface (UUID to open a session with and invoke commands).

The compatible is described in the Linux Documentation but not yet
merged in the linux-next.
It can be found in the tree of arm_scmi driver maintainers:
https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git/log/?h=for-linux-next

This commit:
https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git/commit/?h=for-linux-next&id=b7d2cf7c817b86e705b97f72c6be192a6760a14f

Br,
Etienne

>
>
> >
> > Cheers,
> > Ahmad
> >
> > >
> > > Cc: devicetree@vger.kernel.org
> > > Cc: Rob Herring <robh+dt@kernel.org>
> > > Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
> > > ---
> > > Changes since v6:
> > >  - Remove maxItems from linaro,optee-channel-id description
> > >
> > > No change since v5
> > >
> > > Changes since v4:
> > >  - Fix sram node name in DTS example: s/-shm-/-sram-/
> > >
> > > Changes since v3:
> > >  - Add description for linaro,optee-channel-id in patternProperties
> > >    specifying protocol can optionaly define a dedicated channel id.
> > >  - Fix DTS example (duplicated phandles issue, subnodes ordering)
> > >  - Fix typo in DTS example and description comments.
> > >
> > > Changes since v2:
> > >  - Define mandatory property linaro,optee-channel-id
> > >  - Rebased on yaml description file
> > >
> > > Changes since v1:
> > >  - Removed modification regarding mboxes property description.
> > > ---
> > >  .../bindings/firmware/arm,scmi.yaml           | 65 +++++++++++++++++++
> > >  1 file changed, 65 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> > > index 5c4c6782e052..eae15df36eef 100644
> > > --- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> > > +++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> > > @@ -38,6 +38,9 @@ properties:
> > >                       The virtio transport only supports a single device.
> > >          items:
> > >            - const: arm,scmi-virtio
> > > +      - description: SCMI compliant firmware with OP-TEE transport
> > > +        items:
> > > +          - const: linaro,scmi-optee
> > >
> > >    interrupts:
> > >      description:
> > > @@ -83,6 +86,11 @@ properties:
> > >      description:
> > >        SMC id required when using smc or hvc transports
> > >
> > > +  linaro,optee-channel-id:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description:
> > > +      Channel specifier required when using OP-TEE transport.
> > > +
> > >    protocol@11:
> > >      type: object
> > >      properties:
> > > @@ -195,6 +203,12 @@ patternProperties:
> > >          minItems: 1
> > >          maxItems: 2
> > >
> > > +      linaro,optee-channel-id:
> > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > +        description:
> > > +          Channel specifier required when using OP-TEE transport and
> > > +          protocol has a dedicated communication channel.
> > > +
> > >      required:
> > >        - reg
> > >
> > > @@ -226,6 +240,16 @@ else:
> > >        - arm,smc-id
> > >        - shmem
> > >
> > > +  else:
> > > +    if:
> > > +      properties:
> > > +        compatible:
> > > +          contains:
> > > +            const: linaro,scmi-optee
> > > +    then:
> > > +      required:
> > > +        - linaro,optee-channel-id
> > > +
> > >  examples:
> > >    - |
> > >      firmware {
> > > @@ -340,7 +364,48 @@ examples:
> > >                  reg = <0x11>;
> > >                  #power-domain-cells = <1>;
> > >              };
> > > +        };
> > > +    };
> > > +
> > > +  - |
> > > +    firmware {
> > > +        scmi {
> > > +            compatible = "linaro,scmi-optee";
> > > +            linaro,optee-channel-id = <0>;
> > > +
> > > +            #address-cells = <1>;
> > > +            #size-cells = <0>;
> > > +
> > > +            scmi_dvfs1: protocol@13 {
> > > +                reg = <0x13>;
> > > +                linaro,optee-channel-id = <1>;
> > > +                shmem = <&cpu_optee_lpri0>;
> > > +                #clock-cells = <1>;
> > > +            };
> > > +
> > > +            scmi_clk0: protocol@14 {
> > > +                reg = <0x14>;
> > > +                #clock-cells = <1>;
> > > +            };
> > > +        };
> > > +    };
> > >
> > > +    soc {
> > > +        #address-cells = <2>;
> > > +        #size-cells = <2>;
> > > +
> > > +        sram@51000000 {
> > > +            compatible = "mmio-sram";
> > > +            reg = <0x0 0x51000000 0x0 0x10000>;
> > > +
> > > +            #address-cells = <1>;
> > > +            #size-cells = <1>;
> > > +            ranges = <0 0x0 0x51000000 0x10000>;
> > > +
> > > +            cpu_optee_lpri0: optee-sram-section@0 {
> > > +                compatible = "arm,scmi-shmem";
> > > +                reg = <0x0 0x80>;
> > > +            };
> > >          };
> > >      };
> > >
> >
> >
> > --
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