[PATCH] ARM: Distro boot: document the need for fdtfile variable to be set

[Stephen Warren]

On 9/3/20 10:40 AM, Dennis Gilmore wrote:
> When testing builds provided in https://github.com/openwrt/openwrt/pull/3360
> I discovered that fdtfile was not set and as a result the firmware was not
> functional. So I am documenting what is needed.
> 
> Signed-off-by: Dennis Gilmore <dennis at ausil.us>
> 
> Cc: Atish Patra <atish.patra at wdc.com>
> Cc: Lukas Auer <lukas.auer at aisec.fraunhofer.de>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
> Cc: Vagrant Cascadian <vagrant at debian.org>
> Cc: Stephen Warren <swarren at nvidia.com>
> Cc: Karsten Merker <merker at debian.org>
> ---
>  doc/README.distro | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/doc/README.distro b/doc/README.distro
> index 5076bebd18..3eb70aeb14 100644
> --- a/doc/README.distro
> +++ b/doc/README.distro
> @@ -224,6 +224,14 @@ fdt_addr_r:
>  
>    A size of 1MB for the FDT/DTB seems reasonable.
>  
> +fdtfile:
> +
> +  Mandatory. the name of the DTB file for the specific board for instance
> +  the espressobin v5 board the value is "marvell/armada-3720-espressobin.dtb"
> +  while on a clearfog pro it is "armada-388-clearfog-pro.dtb" in the case of
> +  a board providing its firmware based DTB this value can be used to override
> +  the DTB with a different DTB.

IIRC this variable isn't mandatory; if the DT filename follows expected
${soc}-${board}.dtb naming, then U-Boot has a default value that will
work without the user or U-Boot author having to manually set this variable.

So it's certainly mandatory that U-Boot know this value at runtime, but
perhaps the text should be expanded to indicate that sometimes U-Boot
can provide the value itself, but sometimes the variable needs to be set?