linux-kernel - Re: [PATCH v4 3/4] dt-bindings: mailbox: add binding for Microchip IPC mailbox controller

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Message-ID: <20241126-pulmonary-krypton-30da3faa8482@spud>
Date: Tue, 26 Nov 2024 16:21:13 +0000
From: Conor Dooley <conor@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Valentina Fernandez <valentina.fernandezalanis@...rochip.com>,
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	ycliang@...estech.com, prabhakar.mahadev-lad.rj@...renesas.com,
	peterlin@...estech.com, samuel.holland@...ive.com,
	conor.dooley@...rochip.com, alexghiti@...osinc.com,
	ruanjinjie@...wei.com, takakura@...inux.co.jp, conor+dt@...nel.org,
	jassisinghbrar@...il.com, robh@...nel.org, krzk+dt@...nel.org,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v4 3/4] dt-bindings: mailbox: add binding for Microchip
 IPC mailbox controller

On Tue, Nov 26, 2024 at 08:04:38AM +0100, Krzysztof Kozlowski wrote:
> On Mon, Nov 25, 2024 at 05:58:17PM +0000, Valentina Fernandez wrote:
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - description:
> > +          Intended for use by software running in supervisor privileged
> > +          mode (s-mode). This SBI interface is compatible with the Mi-V
> > +          Inter-hart Communication (IHC) IP.
> > +        const: microchip,sbi-ipc
> > +
> > +      - description:
> > +          Intended for use by the SBI implementation in machine mode
> > +          (m-mode), this compatible string is for the MIV_IHC Soft-IP.
> > +        const: microchip,miv-ihc-rtl-v2

> > +allOf:
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: microchip,sbi-ipc
> > +    then:
> > +      properties:
> > +        reg: false
> 
> What does this mean in reality? Device does not have IO address space?
> Then it is completely different programming model, isn't it?

Ye, different programming models. Two compatibles for the same hardware,
but one represents the m-mode/firmware programming model that has MMIO
access and is the SBI implementation and the other the s-mode/OS
programming model that uses ecalls provided by the SBI implementation.

> > +        microchip,ihc-chan-disabled-mask: false
> > +    else:
> > +      required:
> > +        - reg
> > +        - microchip,ihc-chan-disabled-mask


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