Re: [PATCH v3 2/5] dt-bindings: arm: fsl: add imx-se-fw binding doc

Conor Dooley
2024-06-17T16:37:19Z

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On Mon, Jun 17, 2024 at 12:59:40PM +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 | 160 +++++++++++++++++++++
> 1 file changed, 160 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..60ad1c4a3dfa
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/fsl,imx-se.yaml
> @@ -0,0 +1,160 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/fsl,imx-se.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +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:
> + $nodename:
> + pattern: "^[0-9a-z]*-if@[0-9a-f]+$"

Just "firmware@<hex>" please.

> +
> + compatible:
> + enum:
> + - fsl,imx8ulp-se
> + - fsl,imx93-se
> + - fsl,imx95-se
> +
> + reg:
> + maxItems: 1
> + description: Identifier of the communication interface to secure-enclave.
> +
> + mboxes:
> + description: contain a list of phandles to mailboxes.
> + items:
> + - description: Specify the mailbox used to send message to se 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 communication interface.
> + (see bindings/reserved-memory/reserved-memory.txt)
> +
> + sram:
> + description: contains a list of phandles to sram.

There's only 1 phandle allowed, don't describe it as a list.
Same for memory-region.

> + $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 interface.
> +
> +allOf:
> + # memory-region
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - fsl,imx8ulp-se
> + - fsl,imx93-se
> + then:
> + required:
> + - memory-region

> + else:
> + not:
> + required:
> + - memory-region

Use

else: properties: memory-region: false

Same for sram. Sort the allOf after required.

> +
> + # sram
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - fsl,imx8ulp-se
> + then:
> + required:
> + - sram
> + else:
> + not:
> + required:
> + - sram
> +
> +required:
> + - compatible
> + - reg
> + - mboxes
> + - mbox-names
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + firmware {

You've made up these firmware "buses" here, what purpose do they serve,
other than allowing you to have a reg property?

> + #address-cells = <1>;
> + #size-cells = <0>;
> + ele-if@0 {
> + compatible = "fsl,imx8ulp-se";
> + reg = <0x0>;

What does the reg property even do? Is it ever more than 0? Can this
information be provided as a mbox cell?

> + mboxes = <&s4muap 0 0>, <&s4muap 1 0>;
> + mbox-names = "tx", "rx";
> + sram = <&sram0>;
> + memory-region = <&ele_reserved>;
> + };
> + };
> + - |
> + firmware {

These examples are all basically the same, drop all but one.

Thanks,
Conor.

> + #address-cells = <1>;
> + #size-cells = <0>;
> + ele-if@0 {
> + compatible = "fsl,imx93-se";
> + reg = <0x0>;
> + mboxes = <&s4muap 0 0>, <&s4muap 1 0>;
> + mbox-names = "tx", "rx";
> + memory-region = <&ele_reserved>;
> + };
> + };
> + - |
> + firmware {
> + #address-cells = <1>;
> + #size-cells = <0>;
> + ele-if@0 {
> + compatible = "fsl,imx95-se";
> + reg = <0x0>;
> + mboxes = <&ele_mu0 0 0>, <&ele_mu0 1 0>;
> + mbox-names = "tx", "rx";
> + };
> + v2x-if@3 {
> + compatible = "fsl,imx95-se";
> + reg = <0x3>;
> + mboxes = <&v2x_mu 0 0>, <&v2x_mu 1 0>;
> + mbox-names = "tx", "rx";
> + };
> + v2x-if@4 {
> + compatible = "fsl,imx95-se";
> + reg = <0x4>;
> + mboxes = <&v2x_mu6 0 0>, <&v2x_mu6 1 0>;
> + mbox-names = "tx", "rx";
> + };
> + v2x-if@5 {
> + compatible = "fsl,imx95-se";
> + reg = <0x5>;
> + mboxes = <&v2x_mu7 0 0>, <&v2x_mu7 1 0>;
> + mbox-names = "tx", "rx";
> + };
> + };
> +...
>
> --
> 2.34.1
>

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