Re: [PATCH 3/3] dt-bindings: remoteproc: Add Arm remoteproc

Krzysztof Kozlowski
2024-03-14T13:57:12Z

On 14/03/2024 14:49, Abdellatif El Khlifi wrote:
>> Frankly at the moment I'd be inclined to say it isn't even a remoteproc
>> binding (or driver) at all, it's a reset controller. Bindings are a contract
>> for describing the hardware, not the current state of Linux driver support -
>> if this thing still needs mailboxes, shared memory, a reset vector register,
>> or whatever else to actually be useful, those should be in the binding from
>> day 1 so that a) people can write and deploy correct DTs now, such that
>> functionality becomes available on their systems as soon as driver support
>> catches up, and b) the community has any hope of being able to review
>> whether the binding is appropriately designed and specified for the purpose
>> it intends to serve.
>
> This is an initial patchset for allowing to turn on and off the remote processor.
> The FW is already loaded before the Corstone-1000 SoC is powered on and this
> is done through the FPGA board bootloader in case of the FPGA target.
> Or by the Corstone-1000 FVP model (emulator).
>
> The plan for the driver is as follows:
>
> Step 1: provide a foundation driver capable of turning the core on/off
> Step 2: provide mailbox support for comms
> Step 3: provide FW reload capability
>
> Steps 2 & 3 are waiting for a HW update so the Cortex-A35 (running Linux) can
> share memory with the remote core.
>
> So, when memory sharing becomes available in the FPGA and FVP the
> DT binding will be upgraded with:
>
> - mboxes property specifying the RX/TX mailboxes (based on MHU v2)
> - memory-region property describing the virtio vrings
>
> Currently the mailbox controller does exist in the HW but is not
> usable via virtio (no memory sharing available).
>
> Do you recommend I add the mboxes property even currently we can't do the comms ?

Bindings should be complete, regardless whether Linux driver supports it
or not. Please see writing bindings document for explanation on this and
other rules.

So yes: please describe as much as possible/reasonable.

Best regards,
Krzysztof