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From: Pankaj Gupta <pankaj.gupta@nxp.com>
To: Rob Herring <robh@kernel.org>
CC: Jonathan Corbet <corbet@lwn.net>, Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>,
	Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>, Fabio Estevam
	<festevam@gmail.com>, "linux-doc@vger.kernel.org"
	<linux-doc@vger.kernel.org>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, "devicetree@vger.kernel.org"
	<devicetree@vger.kernel.org>, "imx@lists.linux.dev" <imx@lists.linux.dev>,
	"linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>
Subject: RE: [EXT] Re: [PATCH 2/4] dt-bindings: arm: fsl: add imx-se-fw
 binding doc
Thread-Topic: [EXT] Re: [PATCH 2/4] dt-bindings: arm: fsl: add imx-se-fw
 binding doc
Thread-Index: AQHaot4r694Tqoi2OkK/Xnn0LWMP+LGQ5hKAgAQVonA=
Date: Mon, 13 May 2024 15:36:44 +0000
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References: <20240510-imx-se-if-v1-0-27c5a674916d@nxp.com>
 <20240510-imx-se-if-v1-2-27c5a674916d@nxp.com>
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> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Saturday, May 11, 2024 1:39 AM
> To: Pankaj Gupta <pankaj.gupta@nxp.com>
> Cc: Jonathan Corbet <corbet@lwn.net>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@linaro.org>; Conor Dooley <conor+dt@kernel.org>;
> Shawn Guo <shawnguo@kernel.org>; Sascha Hauer
> <s.hauer@pengutronix.de>; Pengutronix Kernel Team
> <kernel@pengutronix.de>; Fabio Estevam <festevam@gmail.com>; linux-
> doc@vger.kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org; imx@lists.linux.dev; linux-arm-
> kernel@lists.infradead.org
> Subject: [EXT] Re: [PATCH 2/4] dt-bindings: arm: fsl: add imx-se-fw bindi=
ng
> doc
>=20
> Caution: This is an external email. Please take care when clicking links =
or
> opening attachments. When in doubt, report the message using the 'Report
> this email' button
>=20
>=20
> On Fri, May 10, 2024 at 06:57:28PM +0530, Pankaj Gupta wrote:
> > The NXP security hardware IP(s) like: i.MX EdgeLock Enclave, V2X etc.,
> > creates an embedded secure enclave within the SoC boundary to enable
> > features like:
> > - HSM
> > - SHE
> > - V2X
> >
> > Secure-Enclave(s) communication interface are typically via message
> > unit, i.e., based on mailbox linux kernel driver. This driver enables
> > communication ensuring well defined message sequence protocol between
> > Application Core and enclave's firmware.
> >
> > Driver configures multiple misc-device on the MU, for multiple
> > user-space applications, to be able to communicate over single MU.
> >
> > It exists on some i.MX processors. e.g. i.MX8ULP, i.MX93 etc.
> >
> > Signed-off-by: Pankaj Gupta <pankaj.gupta@nxp.com>
> > ---
> >  .../devicetree/bindings/firmware/fsl,imx-se.yaml   | 186
> +++++++++++++++++++++
> >  1 file changed, 186 insertions(+)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/firmware/fsl,imx-se.yaml
> > b/Documentation/devicetree/bindings/firmware/fsl,imx-se.yaml
> > new file mode 100644
> > index 000000000000..a858ef6965cb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/firmware/fsl,imx-se.yaml
> > @@ -0,0 +1,186 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2
> > +---
> > +$id:
> > +https://eur01.safelinks.protection.outlook.com/?url=3Dhttp%3A%2F%2Fdev=
i
> > +cetree.org%2Fschemas%2Ffirmware%2Ffsl%2Cimx-
> se.yaml%23&data=3D05%7C02%7
> >
> +Cpankaj.gupta%40nxp.com%7C2c17789530e9431069b308dc712d0e47%7C
> 686ea1d3
> >
> +bc2b4c6fa92cd99c5c301635%7C0%7C0%7C638509685520936926%7CUnkn
> own%7CTWF
> >
> +pbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJX
> VCI6
> >
> +Mn0%3D%7C0%7C%7C%7C&sdata=3DRwof3k3K1OWimcI5ApRMiyvD%2FPXgk
> b%2BRWrvx76J
> > +YBtw%3D&reserved=3D0
> > +$schema:
> > +https://eur01.safelinks.protection.outlook.com/?url=3Dhttp%3A%2F%2Fdev=
i
> > +cetree.org%2Fmeta-
> schemas%2Fcore.yaml%23&data=3D05%7C02%7Cpankaj.gupta%
> >
> +40nxp.com%7C2c17789530e9431069b308dc712d0e47%7C686ea1d3bc2b4c
> 6fa92cd9
> >
> +9c5c301635%7C0%7C0%7C638509685520944809%7CUnknown%7CTWFpb
> GZsb3d8eyJWI
> >
> +joiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7
> C0%7C%
> >
> +7C%7C&sdata=3Daile3WnYE69fuJHvAOXQARlqLV9roZDuDK63fCj2ZTE%3D&res
> erved=3D0
> > +
> > +title: NXP i.MX HW Secure Enclave(s) EdgeLock Enclave
> > +
> > +maintainers:
> > +  - Pankaj Gupta <pankaj.gupta@nxp.com>
> > +
> > +description: |
> > +  NXP's SoC may contain one or multiple embedded secure-enclave HW
> > +  IP(s) like i.MX EdgeLock Enclave, V2X etc. These NXP's HW IP(s)
> > +  enables features like
> > +    - Hardware Security Module (HSM),
> > +    - Security Hardware Extension (SHE), and
> > +    - Vehicular to Anything (V2X)
> > +
> > +  Communication interface to the secure-enclaves is based on the
> > + messaging unit(s).
> > +
> > +properties:
> > +  '#address-cells':
> > +    const: 1
> > +
> > +  '#size-cells':
> > +    const: 0
> > +
> > +  compatible:
> > +    enum:
> > +      - fsl,imx8ulp-ele
> > +      - fsl,imx93-ele
>=20
> You basically have 0 properties in the parent node. What's the point of i=
t?
> Either just get rid of it and define the child nodes independently or mak=
e the
> parent contain all the resources.
>=20
> > +
> > +patternProperties:
> > +  "^[0-9a-z]*-if@[0-9]+$":
>=20
> unit-addresses are hex.
Accepted.

>=20
> > +    type: object
> > +    description:
> > +      Communication interface to secure-enclave node, that defines
> hardware
> > +      properties to required to establish the communication. There can=
 be
> > +      multiple interfaces to the same secure-enclave. Each interface i=
s
> > +      enumerated with reg property. It optionally defines properties
> > +      depending on the compatible string and interface enum identifier=
.
> > +
> > +    properties:
> > +      reg:
> > +        maxItems: 1
> > +        description: Identifier of the communication interface to secu=
re-
> enclave.
>=20
> What are the identifiers based on?=20
Identifier is used to identify a particular secure enclave interface, withi=
n the multiple secure enclave interfaces under same compatible string.

Secure enclave interface is the combination of:
- messaging unit (hardware), and
- memory constraint applicable to a particular interface.

> Is the value significant to s/w? Kind of looks like you just made up indi=
ces.

For the below example:
    v2x {
      compatible =3D "fsl,imx95-v2x";
      #address-cells =3D <1>;
      #size-cells =3D <0>;

      v2x-if@0 { // if it is not @0, then what identifier to be used to ide=
ntify a particular node.
        reg =3D <0x0>;
        mboxes =3D <&v2x_mu 0 0>, <&v2x_mu 1 0>;
        mbox-names =3D "tx", "rx";
      };
      v2x-if@1 {
        reg =3D <0x1>;
        mboxes =3D <&v2x_mu6 0 0>, <&v2x_mu6 1 0>;
        mbox-names =3D "txdb", "rxdb";
      };
      v2x-if@2 {
        reg =3D <0x2>;
        mboxes =3D <&v2x_mu7 0 0>, <&v2x_mu7 1 0>;
        mbox-names =3D "tx", "rx";
      };
    };
s/w needs to differentiate one node from another node, for the same compati=
ble string for the SoC.=20

>=20
> How many child nodes do you have? Is it fixed per SoC?
It is fixed for a particular SoC.
While number of child nodes varies from one SoC to another SoC.

>=20
> > +
> > +      mboxes:
> > +        description: contain a list of phandles to mailboxes.
> > +        items:
> > +          - description: Specify the mailbox used to send message to s=
e
> firmware
> > +          - description: Specify the mailbox used to receive message
> > + from se firmware
> > +
> > +      mbox-names:
> > +        items:
> > +          - const: tx
> > +          - const: rx
> > +          - const: txdb
> > +          - const: rxdb
> > +        minItems: 2
> > +
> > +      memory-region:
> > +        description: contains a list of phandles to reserved external =
memory.
> > +        items:
> > +          - description: It is used by secure-enclave firmware. It is =
an optional
> > +              property based on compatible and identifier to communica=
tion
> interface.
> > +              (see bindings/reserved-memory/reserved-memory.txt)
> > +
> > +      sram:
> > +        description: contains a list of phandles to sram.
> > +        $ref: /schemas/types.yaml#/definitions/phandle-array
> > +        items:
> > +          - description: Phandle to the device SRAM. It is an optional=
 property
> > +              based on compatible and identifier to communication inte=
rface.
> > +
> > +    required:
> > +      - reg
> > +      - mboxes
> > +      - mbox-names
> > +
> > +allOf:
> > +  # memory-region
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - fsl,imx8ulp-ele
> > +              - fsl,imx93-ele
>=20
> What else would they contain? Those are the only compatibles defined here=
.

It will have multiple child nodes, but fixed number of child node for a par=
ticular SoC.

>=20
> > +    then:
> > +      patternProperties:
> > +        "^[0-9a-z]*-if@[0-9]+$":
> > +          allOf:
> > +            - if:
>=20
> These conditionals are hard to follow. Probably a sign some of this needs=
 to be
> separate or simplified.
I am ready to separate and simplify.=20
Please help by sharing an example on how to go about this change. =20
Probably an example that helps me understand your point and then will start=
 to work on this comment.
It is highly appreciated. Thanks.

>=20
> > +                properties:
> > +                  reg:
> > +                    items:
> > +                      - enum:
> > +                          - 0
> > +              then:
> > +                required:
> > +                  - memory-region
> > +              else:
> > +                not:
> > +                  required:
> > +                    - memory-region
> > +  # sram
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - fsl,imx8ulp-ele
> > +    then:
> > +      patternProperties:
> > +        "^[0-9a-z]*-if@[0-9]+$":
> > +          allOf:
> > +            - if:
> > +                properties:
> > +                  reg:
> > +                    items:
> > +                      - enum:
> > +                          - 0
> > +              then:
> > +                required:
> > +                  - sram
> > +              else:
> > +                not:
> > +                  required:
> > +                    - sram
> > +
> > +additionalProperties: false