Re: [PATCH v6] dt-bindings: arm: keystone: add boot_* mboxes to ti,sci

[Anshul Dalal <anshuld@ti.com>]

On Mon Dec 22, 2025 at 2:23 PM IST, Krzysztof Kozlowski wrote:
> On 22/12/2025 09:43, Anshul Dalal wrote:
>> The bootloader on K3 devices makes use of mailboxes as per the ROM spec
>> which might be different than one's available to the kernel (firmware
>> spec).
>> 
>> Therefore, this patch adds the missing mailbox entries to the DT binding
>> if the matching compatible is ti,am654-sci to represent the mailboxes
>> exposed by the hardware during boot for the purpose of loading the
>> firmware.
>> 
>> The new ti,am642-sci compatible is also added to represent SoCs which do
>> not expose a "notify" channel as part of their TI-SCI spec such as AM64x
>> or the AM62 family. The newly added mboxes are made optional by keeping
>> minItems as 2 to remain compliant with existing device-trees.
>> 
>> Signed-off-by: Anshul Dalal <anshuld@ti.com>
>> ---
>> Changes in v6:
>> - Added ti,am642-sci compatible to represent SoCs without a "notify" channel
>> - Added new examples instead of editing existing ones
>
> Why? Rob asked not to.

I had followed what Nishanth had said[1], I'll wait for him and Rob to
align first before posting the next revision.

[1]: https://lore.kernel.org/linux-devicetree/20251218190449.cnp46cf6hikt6cqa@freebie/

>
>> - Link to v5: https://lore.kernel.org/r/20251215-k3_syscon_add_boot_mailboxes-v5-1-5a8fe567fd31@ti.com
>> 
>> Changes in v5:
>> - Added commit description for the optional mailboxes
>> - Link to v4: https://lore.kernel.org/r/20251205-k3_syscon_add_boot_mailboxes-v4-1-8e216fb88941@ti.com
>> 
>> Changes in v4:
>> - Make new boot_* mboxes conditional on ti,am654-sci compatible
>> - Link to v3: https://lore.kernel.org/r/20251112-k3_syscon_add_boot_mailboxes-v3-1-66155a4236dc@ti.com
>> 
>> Changes in v3:
>> - Drop [1/2] of the last patch series
>> - Update existing example with boot_* mailboxes instead of adding a new one
>> - Link to v2: https://lore.kernel.org/r/20251112-k3_syscon_add_boot_mailboxes-v2-0-aebc1e47b391@ti.com
>> 
>> Changes in v2:
>> - Remove maxItems entry
>> - Remove RFC tag from patch (added by mistake in v1)
>> - Document the new mailboxes in mboxes instead of mbox-names
>> - Provide example with all the mailboxes set
>> - Update commit title to have "ti,sci"
>> - Split into two patches
>> - Link to v1: https://lore.kernel.org/r/20251111-k3_syscon_add_boot_mailboxes-v1-1-529a27f21076@ti.com
>> ---
>>  .../devicetree/bindings/arm/keystone/ti,sci.yaml   | 94 +++++++++++++++++++++-
>>  1 file changed, 91 insertions(+), 3 deletions(-)
>> 
>> diff --git a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> index 25a2b42105e5..0f2c764eae5a 100644
>> --- a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> +++ b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> @@ -40,6 +40,9 @@ properties:
>>        - description: System controller on TI AM654 SoC
>>          items:
>>            - const: ti,am654-sci
>> +      - description: System controller on TI AM642 SoC
>> +        items:
>> +          - const: ti,am642-sci
>
> Why this is not part of enum with previous entries like that?

Yes, I missed adding it. Will fixed in the next revision if the
compatible is still required.

>
>>  
>>    reg-names:
>>      description: |
>> @@ -51,15 +54,15 @@ properties:
>>      minItems: 1
>>  
>>    mbox-names:
>> +    minItems: 2
>> +    maxItems: 6
>>      description: |
>>        Specifies the mailboxes used to communicate with TI-SCI Controller
>>        made available from TI-SCI controller.
>> -    items:
>> -      - const: rx
>> -      - const: tx
>>  
>>    mboxes:
>>      minItems: 2
>> +    maxItems: 6
>>  
>>    ti,host-id:
>>      $ref: /schemas/types.yaml#/definitions/uint32
>> @@ -79,6 +82,66 @@ properties:
>>      type: object
>>      $ref: /schemas/reset/ti,sci-reset.yaml#
>>  
>> +if:
>> +  properties:
>> +    compatible:
>> +      contains:
>> +        const: ti,am654-sci
>> +then:
>> +  properties:
>> +    mbox-names:
>> +      minItems: 2
>> +      items:
>> +        - const: rx
>> +        - const: tx
>> +        - const: notify
>
> Move the notify to the end, so you have only one common list defined at
> the top and you only change number of items per variant.
>
>> +        - const: boot_rx
>> +        - const: boot_tx
>> +        - const: boot_notify
>> +    mboxes:
>> +      minItems: 2
>> +      items:
>> +        - description: RX thread
>> +        - description: TX thread
>> +        - description: Notify thread
>> +        - description: boot stage RX thread
>> +        - description: boot stage TX thread
>> +        - description: boot stage Notify thread
>> +else:
>> +  if:
>
> No, that's not readable. Don't nest these.
>

I agree, perhaps we should drop the new ti,am642-sci compatible and just
reorder the list for ti,am654-sci to: rx, tx, boot_rx, boot_tx,
notify, boot_notify with a minItems of 2 as Nishanth had suggested?

>> +    properties:
>> +      compatible:
>> +        contains:
>> +          const: ti,am642-sci
>> +  then:
>> +    properties:
>> +      mbox-names:
>> +        minItems: 2
>> +        items:
>> +          - const: rx
>> +          - const: tx
>> +          - const: boot_rx
>> +          - const: boot_tx
>> +          - const: boot_notify
>> +      mboxes:
>> +        minItems: 2
>> +        items:
>> +          - description: RX thread
>> +          - description: TX thread
>> +          - description: boot stage RX thread
>> +          - description: boot stage TX thread
>> +          - description: boot stage Notify thread
>> +  else:
>> +    properties:
>> +      mbox-names:
>> +        items:
>> +          - const: rx
>> +          - const: tx
>> +      mboxes:
>> +        items:
>> +          - description: RX thread
>> +          - description: TX thread
>> +
>>  required:
>>    - compatible
>>    - mbox-names
>> @@ -122,3 +185,28 @@ examples:
>>          #reset-cells = <2>;
>>        };
>>      };
>> +
>> +  - |
>> +    system-controller@44083000 {
>> +      compatible = "ti,am654-sci";
>> +      ti,host-id = <4>;
>> +      mbox-names = "rx", "tx", "notify", "boot_rx", "boot_tx";
>> +      mboxes = <&secure_proxy_mcu 6>, <&secure_proxy_mcu 8>,
>> +        <&secure_proxy_mcu 5>, <&secure_proxy_mcu 5>, <&secure_proxy_mcu 4>;
>> +
>> +      reg-names = "debug_messages";
>> +      reg = <0x44083000 0x1000>;
>> +    };
>
> You already have there two examples. You do not need three and for sure
> you do not need four of which two are exactly the same. Rob already
> commented on this.

I can edit the existing example instead if Rob and Nishanth are aligned.

Regards,
Anshul