[PATCH] dt-bindings: nvmem: u-boot, env: add Broadcom's variant binding

[Joel Peshkin]

Hi Rafal,

   The first 32b value is a magic number (endian swapped mnemonic of "uEnv"
short for "u-boot environment").   Finding that magic number of a 4K
boundary followed by a length and then a u-boot environment with a valid
CRC permits a scan of the flash partition to locate the environment without
knowing a-priori where it is.

Regards,

Joel Peshkin


On Wed, Apr 6, 2022 at 8:25 AM Rafał Miłecki <zajec5 at gmail.com> wrote:

> From: Rafał Miłecki <rafal at milecki.pl>
>
> Broadcom uses U-Boot for some of their recent platforms like BCM4908.
> They decided to use modified environment variables variables format
> though. Their header includes 2 extra 32 b fields at the beginning.
>
> The first field meaning is unknown, the second one stores length of env
> data block. Example (length 0x4000):
> $ hexdump -n 32 -C -s 0x40000 /dev/mtdblock0
> 00040000  76 6e 45 75 00 40 00 00  34 89 7a 82 49 4d 41 47  |vnEu.@
> ..4.z.IMAG|
> 00040010  45 3d 4e 41 4e 44 3a 31  4d 2c 31 30 32 34 4d 00
> |E=NAND:1M,1024M.|
>
> Add a custom "compatible" value to allow describing Broadcom devices
> properly.
>
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> ---
>  Documentation/devicetree/bindings/nvmem/u-boot,env.yaml | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> index e70b2a60cb9a..6a6b223be4a0 100644
> --- a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
> @@ -36,6 +36,8 @@ properties:
>          const: u-boot,env-redundant-bool
>        - description: Two redundant blocks with active having higher
> counter
>          const: u-boot,env-redundant-count
> +      - description: Broadcom's variant with custom header
> +        const: brcm,env
>
>    reg:
>      maxItems: 1
> --
> 2.34.1
>
>
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