linux-kernel - Re: [PATCH v5 1/3] dt-bindings: mailbox: add google,gs101-mbox

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Message-ID: <CABb+yY0rBzP8JPAik5aaXp6GivQKEf++sgiMM9fTPgd_5YXT1w@mail.gmail.com>
Date: Fri, 20 Dec 2024 20:19:13 -0600
From: Jassi Brar <jassisinghbrar@...il.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, linux-kernel@...r.kernel.org, 
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, andre.draszik@...aro.org, 
	peter.griffin@...aro.org, kernel-team@...roid.com, willmcvicker@...gle.com, 
	daniel.lezcano@...aro.org, vincent.guittot@...aro.org, ulf.hansson@...aro.org, 
	arnd@...db.de
Subject: Re: [PATCH v5 1/3] dt-bindings: mailbox: add google,gs101-mbox

On Thu, Dec 19, 2024 at 4:51 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
> Hi, Krzysztof, Jassi,
>
> On 12/17/24 9:40 AM, Tudor Ambarus wrote:
>
> > diff --git a/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml b/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml
>
> cut
>
> > +
> > +  '#mbox-cells':
> > +    description: |
> > +      <&phandle type channel>
> > +      phandle : label name of controller.
> > +      type    : channel type, doorbell or data-transfer.
> > +      channel : channel number.
> > +
> > +      Here is how a client can reference them:
> > +      mboxes = <&ap2apm_mailbox DOORBELL 2>;
> > +      mboxes = <&ap2apm_mailbox DATA 3>;
> > +    const: 2
> > +
>
> Revisiting this, I think that for the ACPM interface mailbox client use
> case, it would be better to introduce a mbox property where I reference
> just the phandle to the controller:
>         mbox = <&ap2apm_mailbox>;
>
> The ACPM interface discovers the mailbox channel IDs at runtime by
> parsing SRAM. And all ACPM's channels are of type DOORBELL, thus
> specifying the type and channel in DT is redundant.
>
> It would require to extend a bit the mailbox core to provide a
> mbox_request_channel_by_args() method. I already wrote a draft and
> tested it.
>
> Do you find the idea fine?
>
Looking at v6, I prefer this version... maybe modify it a bit.

Even if you get the channel number at runtime, the type (Data vs
Doorbell) is static and needs to be passed via DT. You may have
  mbox = <&ap2apm_mailbox DOORBELL>;
and in your custom of_xlate implementation return any available
"virtual" channel. You could use 'void *data' in
exynos_mbox_send_data() to pass the h/w channel-id, instead of the
index of the virtual channel.

Thanks.