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

[Krzysztof Kozlowski <krzk@kernel.org>]

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.

> - 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?

>  
>    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.

> +    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.

Best regards,
Krzysztof