Re: [PATCH v13 1/3] dt-bindings: mtd: Describe MTD partitions concatenation

[Rob Herring <robh@kernel.org>]

On Wed, Jun 04, 2025 at 01:12:07AM +0530, Amit Kumar Mahapatra wrote:
> The AMD QSPI controller supports an advanced connection modes called
> Stacked mode which allow the controller to treat two different flashes
> as one storage.
> 
> In Stacked connection mode flashes share the same SPI bus, but different CS
> line, controller driver asserts the CS of the flash to which it needs to
> communicate. Stacked mode is a software abstraction rather than a
> controller feature or capability. At any given time, the controller
> communicates with one of the two connected flash devices, as determined by
> the requested address and data length. If an operation starts on one flash
> and ends on the other, the mtd layer needs to split it into two separate
> operations and adjust the data length accordingly. For more information on
> the modes please feel free to go through the controller flash interface
> below [1].
> 
> To support stacked mode, the existing MTD concat driver has been extended
> to be more generic, enabling multiple sets of MTD partitions to be
> virtually concatenated, with each set forming a distinct logical MTD
> device.
> 
> A new Device Tree property is introduced to facilitate this, containing
> phandles of the partitions to be concatenated with the one where the
> property is defined. This approach supports multiple sets of concatenated
> partitions.
> 
> [1] https://docs.amd.com/r/en-US/am011-versal-acap-trm/QSPI-Flash-Device-Interface
> 
> Suggested-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Suggested-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
> ---
>  .../bindings/mtd/partitions/partition.yaml     | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/partitions/partition.yaml b/Documentation/devicetree/bindings/mtd/partitions/partition.yaml
> index 80d0452a2a33..2ef4bde02cd9 100644
> --- a/Documentation/devicetree/bindings/mtd/partitions/partition.yaml
> +++ b/Documentation/devicetree/bindings/mtd/partitions/partition.yaml
> @@ -57,6 +57,13 @@ properties:
>        user space from
>      type: boolean
>  
> +  part-concat-next:
> +    description: List of phandles to MTD partitions that need be concatenated
> +      with the current partition.
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    minItems: 1
> +    maxItems: 16

Add:

       items:
         maxItems: 1

Because phandle-array is really a matrix.

> +
>    align:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      minimum: 2
> @@ -138,4 +145,15 @@ examples:
>              reg = <0x200000 0x100000>;
>              align = <0x4000>;
>          };
> +
> +        part0: partition@400000 {
> +            part-concat-next = <&part1>;
> +            label = "part0_0";
> +            reg = <0x400000 0x100000>;
> +        };
> +
> +        part1: partition@800000 {
> +            label = "part0_1";
> +            reg = <0x800000 0x800000>;
> +        };
>      };
> -- 
> 2.34.1
>