Hello Krzysztof,

On 1/26/24 12:03, Krzysztof Kozlowski wrote:

On 18/01/2024 11:04, Arnaud Pouliquen wrote:

quoted

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).
For instance, this compatible is used in both the Linux and OP-TEE
device-tree:
- In OP-TEE, a node is defined in the device tree with the
  st,stm32mp1-m4-tee to support signed remoteproc firmware.
  Based on DT properties, OP-TEE authenticates, loads, starts, and stops
  the firmware.
- On Linux, when the compatibility is set, the Cortex-M resets should not
  be declared in the device tree.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
---
V1 to V2 updates
- update "st,stm32mp1-m4" compatible description to generalize
- remove the 'reset-names' requirement in one conditional branch, as the
  property is already part of the condition test.
---
 .../bindings/remoteproc/st,stm32-rproc.yaml   | 52 +++++++++++++++----
 1 file changed, 43 insertions(+), 9 deletions(-)

diff --git a/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml b/Documentation/devicetree/bindings/remoteproc/st,stm32-rproc.yaml
index 370af61d8f28..6af821b15736 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

The patch looks good to me, but I wonder about this choice of two
compatibles.

Basically this is the same hardware with the same interface, but two
compatibles to differentiate a bit different firmware setup. We have
already such cases for Qualcomm [1] [2] and new ones will be coming. [3]

I wonder whether this should be rather the same compatible with
additional property, e.g. "st,tee-control" or "remote-control".

Yes the point is valid, I asked myself the question.

I proposed a compatibility solution for one main reason. On the STM32MP15, if
the firmware is loaded by Linux, no driver is probed in OP-TEE. But if the
firmware is authenticated and loaded by OP-TEE, a Op-TEE driver is probed to
manage memory access rights.

The drawback of a property is that we would need to probe the OP-TEE driver for
the STM32MP1 platform even if it is not used, just to check this property.

Thanks,
Arnaud

[1]
https://elixir.bootlin.com/linux/v6.7.1/source/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml#L54

[2]
https://elixir.bootlin.com/linux/v6.7.1/source/Documentation/devicetree/bindings/net/qcom,ipa.yaml#L129
(that's a bit different)

[3] https://lore.kernel.org/linux-devicetree/20240124103623.GJ4906@thinkpad/ (local)

@Rob,
Any general guidance for this and Qualcomm?

Best regards,
Krzysztof

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