linux-kernel - Re: [PATCH 2/3] dt-bindings: mailbox: starfive: Add StarFive Meu Mailbox Driver

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Message-ID: <20231219-dispute-voicing-0e1c93640954@spud>
Date: Tue, 19 Dec 2023 15:08:45 +0000
From: Conor Dooley <conor@...nel.org>
To: Joshua Yeong <joshua.yeong@...rfivetech.com>
Cc: jeeheng.sia@...rfivetech.com, leyfoon.tan@...rfivetech.com,
	jassisinghbrar@...il.com, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] dt-bindings: mailbox: starfive: Add StarFive Meu
 Mailbox Driver

On Tue, Dec 19, 2023 at 01:52:53PM +0800, Joshua Yeong wrote:
> On 18/12/2023 7:17 PM, Conor Dooley wrote:
> > On Mon, Dec 18, 2023 at 02:12:00PM +0800, Joshua Yeong wrote:
> > > The StarFive Meu Mailbox allow communication between AP and SCP cores
> > > through mailbox doorbell.
> > > 
> > > Co-developed-by: Sia Jee Heng <jeeheng.sia@...rfivetech.com>
> > > Signed-off-by: Sia Jee Heng <jeeheng.sia@...rfivetech.com>
> > > Signed-off-by: Joshua Yeong <joshua.yeong@...rfivetech.com>
> > > Reviewed-by: Ley Foon Tan <leyfoon.tan@...rfivetech.com>
> > > ---
> > >   .../bindings/mailbox/starfive-meu.yaml        | 66 +++++++++++++++++++
> > >   1 file changed, 66 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/mailbox/starfive-meu.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/mailbox/starfive-meu.yaml b/Documentation/devicetree/bindings/mailbox/starfive-meu.yaml
> > > new file mode 100644
> > > index 000000000000..dbc5cfdb90ff
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/mailbox/starfive-meu.yaml
> > > @@ -0,0 +1,66 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/mailbox/starfive-meu.yaml#

Filename should match the compatible.

> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: StarFive MEU Mailbox Controller
> > > +
> > > +maintainers:
> > > +  - Jee Heng Sia <jeeheng.sia@...rfivetech.com>
> > > +  - Joshua Yeong <joshua.yeong@...rfivetech.com>
> > > +
> > > +description: |

This | is not needed, there's no formatting here to preserve.

> > > +  StarFive's Message-Exchange-Unit (MEU) is a mailbox controller that has 62
> > > +  independent doorbells. Each MEU channel consist of 31 doorbells and consist of
> > > +  a pair of Tx/Rx links that shall communicates with remote processor. The
> > > +  sender set the bit in the SET register to indicate data readiness for the
> > > +  receiver. An interrupt will be raised whenever receiving notification doorbell
> > > +  from remote processor. The receiver will clear the bit in the CLR register
> > > +  upon handling the doorbell notification. The sender should poll the STAT
> > > +  register before starting any transaction to ensure all on-going doorbells are
> > > +  processed.
> > What is/are the consumer(s) of this mailbox?
> > Is part of your RPMI implementation?
> > 
> > Cheers,
> > Conor.
> 
> Yes, it would be part of StarFive RPMI implementation.

I see. Seems a bit weird to submit the mailbox provider without a
consumer, since it'll be dead code until a provider arrives, but that's
for the mailbox driver maintainer to decide if he has a problem with.

> 
> Regards,
> Joshua
> 
> > 
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - starfive,jh8100-meu

I would just make this const: starfive,jh8100-meu unless you already
expect your other SoCs to use a different programming model.

> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    items:
> > > +      - description: mailbox0
> > > +      - description: mailbox1
> > > +
> > > +  '#mbox-cells':
> > > +    description: represents index of the mailbox/doorbell paired channel

> > > +      channel  0 - 30 for mailbox0 doorbell
> > > +      channel 31 - 61 for mailbox1 doorbell

I'd probably move this channel to doorbell interrupt mapping into the
main description and leave this as just

'#mbox-cells':
  const: 1

> > > +    const: 1
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - interrupts
> > > +  - '#mbox-cells'
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    soc {
> > > +        #address-cells = <2>;
> > > +        #size-cells = <2>;
> > > +
> > > +        meu: mailbox@...70000 {

Drop the label here, it has no user.

> > > +            compatible = "starfive,jh8100-meu";
> > > +            reg = <0x0 0x1f370000 0 0x8000>;
> > > +            interrupts = <170>, /* Mailbox0 */
> > > +                         <171>; /* Mailbox1 */

I'd also probably drop the comments here, since the binding enforces
this ordering.

Cheers,
Conor.

> > > +            #mbox-cells = <1>;
> > > +        };
> > > +    };
> > > +
> > > +...
> > > -- 
> > > 2.25.1
> > > 

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