Re: [PATCH 2/2] Documentation: user: barebox: mention generic dt 2nd stage support

[Sascha Hauer <sha@pengutronix.de>]

On Mon, Feb 07, 2022 at 09:14:51AM +0100, Ahmad Fatoum wrote:
> Hello Sascha,
> 
> On 07.02.22 09:00, Sascha Hauer wrote:
> > On Sun, Feb 06, 2022 at 12:19:30AM +0100, Ahmad Fatoum wrote:
> >> Most users interested in chainloading barebox will probably want to use
> >> the generic DT format for that: It will pass the checks the boot command
> >> may have and it will ensure the system is in the correct state, e.g.
> >> that caches are disabled.
> >>
> >> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> >> ---
> >>  Documentation/user/barebox.rst | 18 +++++++++++++++---
> >>  1 file changed, 15 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/Documentation/user/barebox.rst b/Documentation/user/barebox.rst
> >> index 8634d8e48eef..4abcf79c6d2a 100644
> >> --- a/Documentation/user/barebox.rst
> >> +++ b/Documentation/user/barebox.rst
> >> @@ -203,9 +203,21 @@ Starting barebox
> >>  Bringing barebox to a board for the first time is highly board specific, see your
> >>  board documentation for initial bringup.
> >>  
> >> -barebox binaries are, where possible, designed to be startable second stage from another
> >> -bootloader. For example, if you have U-Boot running on your board, you can start barebox
> >> -with U-Boot's ``bootm`` command:
> >> +For ARM and RISC-V, the barebox build can additionally generate a generic DT image
> >> +(enable ``CONFIG_BOARD_ARM_GENERIC_DT`` or ``CONFIG_BOARD_RISCV_GENERIC_DT``,
> >> +respectively). The resulting ``images/barebox-dt-2nd.img`` can be booted just
> >> +like a Linux kernel that is passed an external device tree. For example:
> >> +
> >> +.. code-block:: console
> >> +
> >> +  U-Boot: tftp $kernel_addr barebox-dt-2nd.img
> >> +  U-Boot: tftp $fdt_addr my-board.dtb
> >> +  U-Boot: booti $kernel_addr - $fdt_addr
> >> +
> >> +For non-DT enabled-bootloaders or other architectures, often the normal barebox
> >> +binaries can also be used as they are designed to be startable second stage
> >> +from another bootloader, where possible. For example, if you have U-Boot running
> >> +on your board, you can start barebox with U-Boot's ``bootm`` command:
> > 
> > Hm, that seems wrong. U-Boot's bootm command starts images generated
> > with U-Boot's mkimage tool. A raw barebox image cannot be started with
> > this command, one has to create a uImage from it before.
> 
> This is what the documentation is saying right now. It only appeared
> in the diff, because I rephrased the start a bit. I don't have a
> 32-bit ARM U-Boot here to test, so I'd rather not rewrite that part
> myself.

Well you've introduced the part to use the bootm command yourself :)

commit 3a14fb79153af84323fee8308989011cd05c7d96
Author: Ahmad Fatoum <a.fatoum@pengutronix.de>
Date:   Mon Jun 17 16:18:46 2019 +0200

However, I obviously failed to review this properly. I'll create a patch
for that.

Sascha

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