[U-Boot] [PATCH] cmd: pxe: Use internal FDT if external one cannot be retrieved

[Anton Leontiev]

чт, 29 авг. 2019 г. в 23:35, Stephen Warren <swarren at wwwdotorg.org>:
> On 8/29/19 5:20 AM, Anton Leontiev wrote:
> > 2019-08-26 at 18:59, Stephen Warren <swarren at wwwdotorg.org>:
> > We have a GNU/Linux distribution that use FDTDIR in its extlinux.conf
> > to support several boards. But some boards have FDT embedded in U-Boot
> > and it is't present in FDTDIR. In such configuration U-Boot fails to
> > boot an entry, despite no exact FDT is specified in it. Distribution
> > itself is designed to work on any board.
>
> I lookead at that referenced commit description in full and the code,
> and I believe what you want is for U-Boot to set fdt_addr to the
> location of the in-RAM DT, and leave fdt_addr_r unset. This will
> indicate to the pxe code that no FDT should be loaded when parsing
> extlinux.conf, but instead to use fdt_addr directly.
>
> Does that work for you, or does it break some other script/use-case on
> this board?

Indeed, it's a possible option. However, if fdt_addr_r is not set,
user can't override embedded FDT using extlinux.conf. README.distro
says about fdt_addr_r: "This is mandatory even when fdt_addr is
provided, since extlinux.conf must always be able to provide a DTB
which overrides any copy provided by the HW."

So it should be considered as a workaround rather than a solution.

Best regards,
Anton Leontiev