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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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.

Cheers,
Ahmad

> 
> Sascha
> 
> 


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