[PATCH 2/3] dt-bindings: mtd: Add Documentation for Airoha fixed-partitions

[Miquel Raynal]

Hi Christian,

ansuelsmth at gmail.com wrote on Wed, 25 Sep 2024 12:13:58 +0200:

> Add Documentation for Airoha fixed-partitions compatibles.
> 
> Airoha based SoC declare a dedicated partition at the end of the flash to
> store calibration and device specific data, in addition to fixed
> partitions.
> 
> The offset of this special partition is not well defined as a custom bad
> block management driver is used that reserve space at the end of the flash.
> 
> This binding allows defining all fixed partitions and marking the last one
> to detect the correct offset.
> 
> Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
> ---
>  .../partitions/airoha,fixed-partitions.yaml   | 80 +++++++++++++++++++
>  .../bindings/mtd/partitions/partitions.yaml   |  1 +
>  2 files changed, 81 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml b/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> new file mode 100644
> index 000000000000..a45df51065af
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/partitions/airoha,fixed-partitions.yaml
> @@ -0,0 +1,80 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mtd/partitions/airoha,fixed-partitions.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Airoha SoC partitioning
> +
> +description: |
> +  Airoha based SoC declare a dedicated partition at the end of the flash to
> +  store calibration and device specific data, in addition to fixed partitions.
> +
> +  The offset of this special partition is not well defined as a custom bad block
> +  management driver is used that reserve space at the end of the flash.
> +
> +  This binding allows defining all fixed partitions and marking the last one to
> +  detect the correct offset from the new end of the flash.
> +
> +maintainers:
> +  - Christian Marangi <ansuelsmth at gmail.com>
> +
> +select: false
> +
> +properties:
> +  compatible:
> +    const: airoha,fixed-partitions
> +
> +  "#address-cells":
> +    enum: [ 1, 2 ]
> +
> +  "#size-cells":
> +    enum: [ 1, 2 ]
> +
> +patternProperties:
> +  "^partition@[0-9a-f]+$":
> +    $ref: partition.yaml#
> +    properties:
> +      compatible:
> +        const: airoha,dynamic-art
> +    unevaluatedProperties: false
> +
> +required:
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    partitions {
> +        compatible = "airoha,fixed-partitions";
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +
> +        partition at 0 {
> +          label = "bootloader";
> +          reg = <0x00000000 0x00080000>;
> +        };
> +
> +        partition at 80000 {
> +          label = "tclinux";
> +          reg = <0x00080000 0x02800000>;
> +        };
> +
> +        partition at 2880000 {
> +          label = "tclinux_slave";
> +          reg = <0x02880000 0x02800000>;
> +        };
> +
> +        partition at 5080000 {
> +          label = "rootfs_data";
> +          reg = <0x5080000 0x00800000>;
> +        };
> +
> +        partition at ffffffff {
> +          compatible = "airoha,dynamic-art";
> +          label = "art";
> +          reg = <0xffffffff 0x00300000>;

I'm a little bit puzzled by this kind of information which is known to
be wrong. As the partition offset and size must be dynamically
calculated, this reg property (as well as the size parameter of the
previous one) are notably wrong. I guess we are not fully constrained
by the fixed-partitions schema here, so could we avoid the reg property
in the airoha,dynamic-art partition? Maybe we also need a #define for a
specific placeholder in the penultimate reg property too (for the size).

Thanks,
Miquèl