Re: [PATCH v5] dt-bindings: arm: keystone: add boot_* mboxes to ti,sci

[Anshul Dalal <anshuld@ti.com>]

> On 11:38-20251215, 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 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 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   | 50 +++++++++++++++++++---
>>  1 file changed, 43 insertions(+), 7 deletions(-)
>> 
>> diff --git a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> index 25a2b42105e5..d9eb2a81e539 100644
>> --- a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> +++ b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
>> @@ -51,15 +51,15 @@ 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 +79,42 @@ 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
>> +        - 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:
>> +  properties:
>> +    mbox-names:
>> +      items:
>> +        - const: rx
>> +        - const: tx
>> +    mboxes:
>> +      items:
>> +        - description: RX thread
>> +        - description: TX thread
>> +
>>  required:
>>    - compatible
>>    - mbox-names
>> @@ -99,11 +135,11 @@ examples:
>>  
>>    - |
>>      dmsc: system-controller@44083000 {
>> -      compatible = "ti,k2g-sci";
>> +      compatible = "ti,am654-sci";
>>        ti,host-id = <12>;
>> -      mbox-names = "rx", "tx";
>> -      mboxes = <&secure_proxy_main 11>,
>> -               <&secure_proxy_main 13>;
>> +      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>;
>
> Please add a different example for am654, i want to make sure k2g still
> continues to be checked.
>
> That said, AM62 series of devices do not use notification pipe for
> standard communication. So, the schema will break for those.
>
> in summary:
> k2g: rx, tx
> am654, j721e, j721s2, j7200, j784s4, .. : rx, tx, notify, boot_rx,
> boot_tx, boot_notify
> am625, am62p ..: rx, tx, boot_rx, boot_tx, boot_notify
>
> we will need three examples, and will need to add am62x series as one
> additional compatible.
>
> Though we could play a trick by reordering as follows to handle superset
> of am62 and am65 series as follows, but I do prefer explicitly handling
> them:
>
>    - const: rx
>    - const: tx
>    - const: boot_rx
>    - const: boot_tx
>    - const: notify
>    - const: boot_notify

I'm in favour of adding the new compatible for the AM62 devices and
handling the mboxes properly, let's fix it properly this time :)

Will post a v6 shortly,
~ Anshul