Re: [PATCH v19 4/6] dt-bindings: remoteproc: Add compatibility for TEE support

Hi Arnaud,

First of all apologies for such a late review comment as previously I wasn't CCed or involved in the review of this patch-set. In case any of my following comments have been discussed in the past then feel free to point me at relevant discussions.

On Wed, Jun 25, 2025 at 11:40:26AM +0200, Arnaud Pouliquen wrote:

The "st,stm32mp1-m4-tee" compatible is utilized in a system configuration where the Cortex-M4 firmware is loaded by the Trusted Execution Environment (TEE).

Having a DT based compatible for a TEE service to me just feels like it is redundant here. I can see you have also used a TEE bus based device too but that is not being properly used. I know subsystems like remoteproc, SCMI and others heavily rely on DT to hardcode properties of system firmware which are rather better to be discovered dynamically.

So I have an open question for you and the remoteproc subsystem maintainers being:

Is it feasible to rather leverage the benefits of a fully discoverable TEE bus rather than relying on platform bus/ DT to hardcode firmware properties?

For instance, this compatible is used in both the Linux and OP-TEE device trees:

• In OP-TEE, a node is defined in the device tree with the "st,stm32mp1-m4-tee" compatible to support signed remoteproc firmware. Based on DT properties, the OP-TEE remoteproc framework is initiated to expose a trusted application service to authenticate and load the remote processor firmware provided by the Linux remoteproc framework, as well as to start and stop the remote processor.
• In Linux, when the compatibility is set, the Cortex-M resets should not be declared in the device tree. In such a configuration, the reset is managed by the OP-TEE remoteproc driver and is no longer accessible from the Linux kernel.

Associated with this new compatible, add the "st,proc-id" property to identify the remote processor. This ID is used to define a unique ID, common between Linux, U-Boot, and OP-TEE, to identify a coprocessor.

This "st,proc-id" is just one such property which can rather be directly probed from the TEE/OP-TEE service rather than hardcoding it in DT here. I think the same will apply to other properties as well.

-Sumit

This ID will be used in requests to the OP-TEE remoteproc Trusted Application to specify the remote processor.

Signed-off-by: Arnaud Pouliquen arnaud.pouliquen@foss.st.com Reviewed-by: Rob Herring (Arm) robh@kernel.org

---

.../bindings/remoteproc/st,stm32-rproc.yaml | 58 ++++++++++++++++--- 1 file changed, 50 insertions(+), 8 deletions(-)

diff --git a/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml b/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml index 843679c557e7..58da07e536fc 100644 --- a/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml +++ b/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml @@ -16,7 +16,12 @@ maintainers: properties: compatible:

• const: st,stm32mp1-m4

• enum:

•  - st,stm32mp1-m4
  

•  - st,stm32mp1-m4-tee
  

• description:

•  Use "st,stm32mp1-m4" for the Cortex-M4 coprocessor management by non-secure context
  

•  Use "st,stm32mp1-m4-tee" for the Cortex-M4 coprocessor management by secure context
  

reg: description: @@ -43,6 +48,10 @@ properties: - description: The offset of the hold boot setting register - description: The field mask of the hold boot

• st,proc-id:
• description: remote processor identifier
• $ref: /schemas/types.yaml#/definitions/uint32
• st,syscfg-tz: deprecated: true description:

@@ -146,21 +155,43 @@ properties: required:

• compatible
• reg
• • resets

allOf:

• if: properties:

•    reset-names:
  

•      not:
  

•        contains:
  

•          const: hold_boot
  

•    compatible:
  

•      contains:
  

•        const: st,stm32mp1-m4
  

  then:

•  if:
  

•    properties:
  

•      reset-names:
  

•        not:
  

•          contains:
  

•            const: hold_boot
  

•  then:
  

•    required:
  

•      - st,syscfg-holdboot
  

•  else:
  

•    properties:
  

•      st,syscfg-holdboot: false
  

•    required:
  

•      - reset-names
   required:
  

•    - st,syscfg-holdboot
  

• else:

•    - resets
  

• • if:

•  properties:
  

•    compatible:
  

•      contains:
  

•        const: st,stm32mp1-m4-tee
  

• then: properties: st,syscfg-holdboot: false

•    reset-names: false
  

•    resets: false
  

•  required:
  

•    - st,proc-id
  

additionalProperties: false @@ -192,5 +223,16 @@ examples: st,syscfg-rsc-tbl = <&tamp 0x144 0xFFFFFFFF>; st,syscfg-m4-state = <&tamp 0x148 0xFFFFFFFF>; };

• • |
• #include <dt-bindings/reset/stm32mp1-resets.h>
• m4@10000000 {

•  compatible = "st,stm32mp1-m4-tee";
  

•  reg = <0x10000000 0x40000>,
  

•        <0x30000000 0x40000>,
  

•        <0x38000000 0x10000>;
  

•  st,proc-id = <0>;
  

•  st,syscfg-rsc-tbl = <&tamp 0x144 0xFFFFFFFF>;
  

•  st,syscfg-m4-state = <&tamp 0x148 0xFFFFFFFF>;
  

• };

... -- 2.25.1