linux-kernel - Re: [PATCH 2/2] dt-bindings: mailbox: Add devicetree binding for bcm74110 mbox

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Message-ID: <cb0905ec-1e80-4c56-befd-b90243dcfa31@broadcom.com>
Date: Fri, 28 Mar 2025 11:36:53 -0700
From: Justin Chen <justin.chen@...adcom.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: florian.fainelli@...adcom.com, conor+dt@...nel.org, krzk+dt@...nel.org,
 robh@...nel.org, jassisinghbrar@...il.com,
 bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 2/2] dt-bindings: mailbox: Add devicetree binding for
 bcm74110 mbox



On 3/28/25 12:31 AM, Krzysztof Kozlowski wrote:
> On 27/03/2025 23:16, justin.chen@...adcom.com wrote:
>> From: Justin Chen <justin.chen@...adcom.com>
>>
>> Add devicetree YAML binding for brcmstb bcm74110 mailbox used
>> for communicating with a co-processor.
>>
>> Signed-off-by: Justin Chen <justin.chen@...adcom.com>
> 
> Bindings are before users, see DT submitting patches.
> 
>> ---
>>   .../bindings/mailbox/brcm,bcm74110-mbox.yaml  | 68 +++++++++++++++++++
>>   1 file changed, 68 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/mailbox/brcm,bcm74110-mbox.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/mailbox/brcm,bcm74110-mbox.yaml b/Documentation/devicetree/bindings/mailbox/brcm,bcm74110-mbox.yaml
>> new file mode 100644
>> index 000000000000..139728a35303
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mailbox/brcm,bcm74110-mbox.yaml
>> @@ -0,0 +1,68 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/mailbox/brcm,bcm74110-mbox.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Broadcom BCM74110 Mailbox Driver
> 
> Driver as Linux driver? Drop, bindings describe hardware.
> 
>> +
>> +maintainers:
>> +  - Justin Chen <justin.chen@...adcom.com>
>> +  - Florian Fainelli <florian.fainelli@...adcom.com>
>> +
>> +description: Broadcom mailbox driver first introduced with 74110
> 
> Same comments.
> 
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - brcm,bcm74110-mbox
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  "#mbox-cells":
>> +    const: 2
>> +    description:
>> +      The first cell is channel type and second cell is shared memory slot
>> +
>> +  brcm,mbox_tx:
> 
> No underscores. See DTS coding style.
> 

Acked. I already had this fixed in the driver, but not in the doc. Woops!

>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: Mailbox transmit doorbell
> 
> Why is this needed in DT? How many instances do you have in one SoC?
> Where is the SoC DTS?
> 

We have 3 possible instances in our current SoC. We currently only 
implement one. arm,scmi. But more will come in the future. I'll put a 
sample arm,scmi node as an example consumer in v2.

>> +
>> +  brcm,mbox_rx:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: Mailbox receive doorbell
>> +
>> +  brcm,mbox_shmem:
>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>> +    maxItems: 2
>> +    description: Mailbox shared memory region and size
> 
> No, use existing properties, e.g. memory region.
> 

This is a region from the on chip memory. I will rename to be clear. It 
lies in a different address space as reserved-memory. I can still use 
memory region if you prefer, but I will need to manually strip the 
offset in my driver as the API agreed upon with the FW is an offset from 
the beginning of on chip memory. IMHO this makes things unnecessarily 
complicated.

>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - interrupts
>> +  - "#mbox-cells"
>> +  - brcm,mbox_tx
>> +  - brcm,mbox_rx
>> +  - brcm,mbox_shmem
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/interrupt-controller/irq.h>
>> +
>> +        brcm_pmc_mailbox: brcm_pmc_mailbox@...2000 {
> 
> Use indentation we expect. See writing schema, example-schema.
> 
>> +                #mbox-cells = <2>;
>> +                compatible = "brcm,bcm74110-mbox";
> 
> Fix order, see DTS coding style.
> 
> 
> 

Thanks for the review.
Justin

> Best regards,
> Krzysztof