Re: [RFC PATCH v2 03/17] dt-bindings: mailbox: Add bindings for RISC-V SBI MPXY extension

[Anup Patel <apatel@ventanamicro.com>]

On Tue, Feb 4, 2025 at 4:14 AM Rob Herring <robh@kernel.org> wrote:
>
> On Mon, Feb 03, 2025 at 02:18:52PM +0530, Anup Patel wrote:
> > Add device tree bindings for the RISC-V SBI Message Proxy (MPXY)
> > extension as a mailbox controller.
> >
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> >  .../bindings/mailbox/riscv,sbi-mpxy-mbox.yaml | 54 +++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml b/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> > new file mode 100644
> > index 000000000000..8a05e089b710
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> > @@ -0,0 +1,54 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mailbox/riscv,sbi-mpxy-mbox.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: RISC-V SBI Message Proxy (MPXY) extension based mailbox
> > +
> > +maintainers:
> > +  - Anup Patel <anup@brainfault.org>
> > +
> > +description: |
> > +  The RISC-V SBI Message Proxy (MPXY) extension [1] allows supervisor
> > +  software to send messages through the SBI implementation (M-mode
> > +  firmware or HS-mode hypervisor). The underlying message protocol
> > +  and message format used by the supervisor software could be some
> > +  other standard protocol compatible with the SBI MPXY extension
> > +  (such as RISC-V Platform Management Interface (RPMI) [2]).
> > +
> > +  ===========================================
> > +  References
> > +  ===========================================
> > +
> > +  [1] RISC-V Supervisor Binary Interface (SBI)
> > +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> > +
> > +  [2] RISC-V Platform Management Interface (RPMI)
> > +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> > +
> > +properties:
> > +  $nodename:
> > +    const: sbi-mpxy-mbox
>
> 'mailbox' is the defined name for mailbox providers.

Okay, I will update.

>
> > +
> > +  compatible:
> > +    const: riscv,sbi-mpxy-mbox
> > +
> > +  "#mbox-cells":
> > +    const: 2
> > +    description:
> > +      The first cell specifies channel_id of the SBI MPXY channel,
> > +      the second cell specifies MSG_PROT_ID of the SBI MPXY channel
> > +
> > +required:
> > +  - compatible
> > +  - "#mbox-cells"
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    sbi-mpxy-mbox {
> > +          compatible = "riscv,sbi-mpxy-mbox";
> > +          #mbox-cells = <2>;
>
> Is there an SBI node? #mbox-cells could just be part of that along with
> anything else that SBI is a provider for. And we already have the PMU
> SBI binding. It's all one thing, so there should be one SBI node. Then
> we can debate about child nodes of it.

There is no SBI node for any other SBI extension.

The PMU bindings for "riscv,pmu" compatible string is for the firmware
driver (M-mode) which implements the SBI PMU extension not the Linux
driver.

The "title" and "description" of
<linux_source>/Documentation/devicetree/bindings/perf/riscv,pmu.yaml
needs some clarification.

Regards,
Anup