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SubjectRe: [PATCH 2/4] dt-bindings: arm: fsl: add imx-se-fw binding doc
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
> +---
> +$id: http://devicetree.org/schemas/firmware/fsl,imx-se.yaml#
> +$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:
> + '#address-cells':
> + const: 1
> +
> + '#size-cells':
> + const: 0
> +
> + compatible:
> + enum:
> + - fsl,imx8ulp-ele
> + - fsl,imx93-ele

You basically have 0 properties in the parent node. What's the point of
it? Either just get rid of it and define the child nodes independently
or make the parent contain all the resources.

> +
> +patternProperties:
> + "^[0-9a-z]*-if@[0-9]+$":

unit-addresses are hex.

> + 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 is
> + 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 secure-enclave.

What are the identifiers based on? Is the value significant to s/w? Kind
of looks like you just made up indices.

How many child nodes do you have? Is it fixed per SoC?

> +
> + 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.
> + $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.
> +
> + required:
> + - reg
> + - mboxes
> + - mbox-names
> +
> +allOf:
> + # memory-region
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - fsl,imx8ulp-ele
> + - fsl,imx93-ele

What else would they contain? Those are the only compatibles defined
here.

> + then:
> + patternProperties:
> + "^[0-9a-z]*-if@[0-9]+$":
> + allOf:
> + - if:

These conditionals are hard to follow. Probably a sign some of this
needs to be separate or simplified.

> + 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

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