Re: [PATCH v2 1/2] dt-bindings: remoteproc: Add C906L rproc for Sophgo CV1800B SoC

[Junhui Liu]

On 29/07/2025 16:31, Inochi Amaoto wrote:
> On Mon, Jul 28, 2025 at 07:03:23PM +0800, Junhui Liu wrote:
>> Add C906L remote processor for CV1800B SoC, which is an asymmetric
>> processor typically running RTOS.
>> 
>> Signed-off-by: Junhui Liu <junhui.liu@xxxxxxxxxxxxx>
>> ---
>>  .../bindings/remoteproc/sophgo,cv1800b-c906l.yaml  | 79 ++++++++++++++++++++++
>>  1 file changed, 79 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml b/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..2061c2fd6ba343c09b1a91700ea4a695d2b57f81
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml
>> @@ -0,0 +1,79 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/remoteproc/sophgo,cv1800b-c906l.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Sophgo C906L remote processor controller for CV1800B SoC
>> +
>> +maintainers:
>> +  - Junhui Liu <junhui.liu@xxxxxxxxxxxxx>
>> +
>> +description:
>> +  Document the bindings for the C906L remoteproc component that loads and boots
>> +  firmwares on the CV1800B SoC.
>> +
>> +properties:
>> +  compatible:
>> +    const: sophgo,cv1800b-c906l
>> +
>> +  firmware-name:
>> +    maxItems: 1
>> +
>> +  mbox-names:
>> +    items:
>> +      - const: tx
>> +      - const: rx
>> +
>> +  mboxes:
>> +    description:
>> +      This property is required only if the rpmsg/virtio functionality is used.
>> +      (see mailbox/sophgo,cv1800b-mailbox.yaml)
>> +    items:
>> +      - description: mailbox channel to send data to C906L
>> +      - description: mailbox channel to receive data from C906L
>> +
>> +  memory-region:
>> +    description:
>> +      List of phandles to reserved memory regions used by the remote processor.
>> +      The first region is required and provides the firmware region for the
>> +      remote processor. The following regions (vdev buffer, vrings) are optional
>> +      and are only required if rpmsg/virtio functionality is used.
>> +    minItems: 1
>> +    items:
>> +      - description: firmware region
>> +      - description: vdev buffer
>> +      - description: vring0
>> +      - description: vring1
>> +    additionalItems: true
>> +
> 
> Why not allocating these region dynamicly? I do not think firware is
> always avaible before staring. Allowing dynamic firmware give us max
> flexiblity.

I'm afraid it's not easy to do this.

For firmware region, the RTOS firmware usually needs a physical address
to link to, and I have researched and tested two RTOS (RT-Thread and
Zephyr) on the C906L, both of them do not support position-independent
execution or runtime relocation. Therefore, a reserved memory region is
needed to provide a fixed physical address for the RTOS firmware.
(In fact, there is already a reserved memory region for the C906L in
cv1800b-milkv-duo.dts)

For virtio-related regions, the RTOS firmware also needs to know the
shared memory regions for communications at compile time.

So, reserving memory through DT is necessary for now.

> 
> Regards,
> Inochi

-- 
Best regards,
Junhui Liu