Re: [PATCH v1 2/5] dt-bindings: mailbox: add binding for Microchip IPC mailbox driver

[Samuel Holland]

Hi Valentina,

On 2024-09-12 12:00 PM, Valentina Fernandez wrote:
> Add a dt-binding for the Microchip Inter-Processor Communication (IPC)
> mailbox controller.
> 
> Signed-off-by: Valentina Fernandez <valentina.fernandezalanis@xxxxxxxxxxxxx>
> ---
>  .../bindings/mailbox/microchip,sbi-ipc.yaml   | 115 ++++++++++++++++++
>  1 file changed, 115 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/microchip,sbi-ipc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/microchip,sbi-ipc.yaml b/Documentation/devicetree/bindings/mailbox/microchip,sbi-ipc.yaml
> new file mode 100644
> index 000000000000..dc2cbd5eb28f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/microchip,sbi-ipc.yaml
> @@ -0,0 +1,115 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mailbox/microchip,sbi-ipc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip Inter-processor communication (IPC) mailbox controller
> +
> +maintainers:
> +  - Valentina Fernandez <valentina.fernandezalanis@xxxxxxxxxxxxx>
> +
> +description:
> +  The Microchip Inter-processor Communication (IPC) facilitates
> +  message passing between processors using an interrupt signaling
> +  mechanism.
> +  This SBI interface is compatible with the Mi-V Inter-hart
> +  Communication (IHC) IP.
> +  The microchip,sbi-ipc compatible string is inteded for use by software
> +  running in supervisor privileged mode (s-mode). The SoC-specific
> +  compatibles are inteded for use by the SBI implementation in machine
> +  mode (m-mode).

There is a lot of conditional logic in this binding for how small it is. Would
it make sense to split this into two separate bindings? For example, with the
current binding microchip,ihc-chan-disabled-mask is allowed for the SBI
interface, but doesn't look like it belongs there.

> +
> +properties:
> +  compatible:
> +    enum:
> +      - microchip,sbi-ipc
> +      - microchip,miv-ihc-rtl-v2
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    minItems: 1
> +    maxItems: 5
> +
> +  interrupt-names:
> +    minItems: 1
> +    maxItems: 5
> +
> +  "#mbox-cells":
> +    description:
> +      For the SBI "device", the cell represents the global "logical" channel IDs.
> +      The meaning of channel IDs are platform firmware dependent. The
> +      SoC-specific compatibles are intended for use by the SBI implementation,
> +      rather than s-mode software. There the cell would represent the physical
> +      channel and do not vary depending on platform firmware.
> +    const: 1
> +
> +  microchip,ihc-chan-disabled-mask:
> +    description:
> +      Represents the enable/disable state of the bi-directional IHC channels
> +      within the MIV-IHC IP configuration. The mask is a 16-bit value, but only
> +      the first 15 bits are utilized.Each of the bits corresponds to
> +      one of the 15 IHC channels.
> +      A bit set to '1' indicates that the corresponding channel is disabled,
> +      and any read or write operations to that channel will return zero.
> +      A bit set to '0' indicates that the corresponding channel is enabled
> +      and will be accessible through its dedicated address range registers.
> +      The remaining bit of the 16-bit mask is reserved and should be ignored.
> +      The actual enable/disable state of each channel is determined by the
> +      IP block’s configuration.
> +    $ref: /schemas/types.yaml#/definitions/uint16
> +    default: 0
> +
> +required:
> +  - compatible
> +  - interrupts
> +  - interrupt-names
> +  - "#mbox-cells"
> +
> +additionalProperties: false
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: microchip,sbi-ipc
> +    then:
> +      properties:
> +        reg: false
> +    else:
> +      required:
> +        - reg
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: microchip,miv-ihc-rtl-v2
> +    then:
> +      properties:
> +        interrupt-names:
> +          items:
> +            pattern: "^hart-[0-5]+$"

The driver in patch 3 uses this pattern for the SBI interface, so should it
apply there as well?

Regards,
Samuel

> +
> +examples:
> +  - |
> +    mailbox {
> +      compatible = "microchip,sbi-ipc";
> +      interrupt-parent = <&plic>;
> +      interrupts = <180>, <179>, <178>;
> +      interrupt-names = "hart-1", "hart-2", "hart-3";
> +      #mbox-cells = <1>;
> +    };
> +  - |
> +    mailbox@50000000 {
> +      compatible = "microchip,miv-ihc-rtl-v2";
> +      microchip,ihc-chan-disabled-mask=  /bits/ 16 <0>;
> +      reg = <0x50000000 0x1C000>;
> +      interrupt-parent = <&plic>;
> +      interrupts = <180>, <179>, <178>;
> +      interrupt-names = "hart-1", "hart-2", "hart-3";
> +      #mbox-cells = <1>;
> +    };