linux-kernel - RE: [PATCH v4 1/2] dt-bindings: mailbox: Add ASPEED AST2700 series SoC

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Message-ID:
 <TYZPR06MB656882B1D5BA4CB72D19AA9DF17BA@TYZPR06MB6568.apcprd06.prod.outlook.com>
Date: Wed, 25 Jun 2025 03:03:03 +0000
From: Jammy Huang <jammy_huang@...eedtech.com>
To: Andrew Jeffery <andrew@...econstruct.com.au>, "jassisinghbrar@...il.com"
	<jassisinghbrar@...il.com>, "robh@...nel.org" <robh@...nel.org>,
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org"
	<conor+dt@...nel.org>, "joel@....id.au" <joel@....id.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-aspeed@...ts.ozlabs.org"
	<linux-aspeed@...ts.ozlabs.org>
CC: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: RE: [PATCH v4 1/2] dt-bindings: mailbox: Add ASPEED AST2700 series
 SoC

> On Wed, 2025-06-25 at 00:34 +0000, Jammy Huang wrote:
> > >
> > > On Mon, 2025-06-23 at 10:44 +0800, Jammy Huang wrote:
> > > > Introduce the mailbox module for AST27XX series SoC, which is
> > > > responsible for interchanging messages between asymmetric processors.
> > > >
> > > > Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
> > > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > > ---
> > > >  .../mailbox/aspeed,ast2700-mailbox.yaml       | 57
> > > > +++++++++++++++++++
> > > >  1 file changed, 57 insertions(+)
> > > >  create mode 100644
> > > > Documentation/devicetree/bindings/mailbox/aspeed,ast2700-mailbox.y
> > > > aml
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/mailbox/aspeed,ast2700-mailbox
> > > > .yam
> > > > l
> > > > b/Documentation/devicetree/bindings/mailbox/aspeed,ast2700-mailbox
> > > > .yam
> > > > l
> > > > new file mode 100644
> > > > index 000000000000..9c5d7028e116
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/mailbox/aspeed,ast2700-mai
> > > > +++ lbox
> > > > +++ .yaml
> > > > @@ -0,0 +1,57 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) %YAML 1.2
> > > > +---
> > > > +$id:
> > > > +http://devicetree.org/schemas/mailbox/aspeed,ast2700-mailbox.yaml
> > > > +#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: ASPEED AST2700 mailbox controller
> > > > +
> > > > +maintainers:
> > > > +  - Jammy Huang <jammy_huang@...eedtech.com>
> > > > +
> > > > +description:
> > > > +  ASPEED AST2700 has multiple processors that need to communicate
> > > > +with each
> > > > +  other. The mailbox controller provides a way for these
> > > > +processors to send
> > > > +  messages to each other. It is a hardware-based inter-processor
> > > > +communication
> > > > +  mechanism that allows processors to send and receive messages
> > > > +through
> > > > +  dedicated channels.
> > > > +  The mailbox's tx/rx are independent, meaning that one processor
> > > > +can send a
> > > > +  message while another processor is receiving a message
> simultaneously.
> > > > +  There are 4 channels available for both tx and rx operations.
> > > > +Each channel
> > > > +  has a FIFO buffer that can hold messages of a fixed size (32
> > > > +bytes in this
> > > > +  case).
> > > > +  The mailbox controller also supports interrupt generation,
> > > > +allowing
> > > > +  processors to notify each other when a message is available or
> > > > +when an event
> > > > +  occurs.
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: aspeed,ast2700-mailbox
> > > > +
> > > > +  reg:
> > > > +    maxItems: 1
> > > > +
> > > > +  interrupts:
> > > > +    maxItems: 1
> > > > +
> > > > +  "#mbox-cells":
> > > > +    const: 1
> > > > +
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - interrupts
> > > > +  - "#mbox-cells"
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > +  - |
> > > > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > > > +
> > > > +    mailbox@...1c200 {
> > > > +        compatible = "aspeed,ast2700-mailbox";
> > > > +        reg = <0x12c1c200 0x200>;
> > >
> > > I realise this is just an example, but with respect to the
> > > datasheet, shouldn't this be sized as 0x100?
> > >
> > I use 0x200 here because I want to include tx/rx together in one
> > mailbox controller instance.
> > Ex. 0x12c1c200 is a IPC whose TX is NS-CA35 and RX is SSP.
> > 0x12c1c300 is a IPC whose TX is SSP and RX is NS-CA35.
> 
> What do you think of instead requiring two reg items? One for the TX block
> and another for RX. I feel that aligns better with the way the blocks are
> desribed in the datasheet, even if TX and RX happen to be contiguous for a
> given remote side in the current design.
Agree. I will modify accordingly.

> 
> Andrew

Regards
Jammy