Hello Sumit,
On 9/16/25 11:14, Sumit Garg wrote:
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.
No worries, there are too many versions of this series to follow all the
past discussions. I sometimes have difficulty remembering all the
discussions myself :)
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?
The discoverable TEE bus does not works if the remoteproc is probed
before the OP-TEE bus, in such case no possibility to know if the TEE
TA is not yet available or not available at all.
This point is mentioned in a comment in rproc_tee_register().
Then, it is not only a firmware property in our case. Depending on the
compatible string, we manage the hardware differently. The same compatibles
are used in both OP-TEE and Linux. Based on the compatible, we can assign
memories, clocks, and resets to either the secure or non-secure context.
This approach is implemented on the STM32MP15 and STM32MP2x platforms.
More details are available in the ST WIKI:
https://wiki.st.com/stm32mpu/wiki/OP-TEE_remoteproc_framework_overview#Device_tree_configuration
https://wiki.st.com/stm32mpu/wiki/Linux_remoteproc_framework_overview#Device_tree_configuration
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.
Do you mean a topology discovery mechanism through the TEE remoteproc
service?
For the STM32MP15, it could work since we have only one remote processor.
However, this is not the case for the STM32MP25, which embeds both a
Cortex-M33 and a Cortex-M0.
Could you please elaborate on how you see the support of multiple remote
processors without using an hardcoded identifier?
I think the same will apply to other properties as well.
Could you details the other properties you have in mind?
Thanks,
Arnaud
-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 <[email protected]>
Reviewed-by: Rob Herring (Arm) <[email protected]>
---
.../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
