[PATCH] arm: kirkwood: Enable uart0 dm-pre-reloc for Kirkwood boards

[Michael Walle]

>> > When DM_SERIAL is enabled, the device-tree property dm-pre-reloc is
>> > required to boot over UART with kwboot. Enable this in a Kirkwood
>> > common u-boot dtsi.
>> 
>> My (dev) board unfortunately, have a bootloader which can't boot over
>> serial.
> 
> This is feature of Marvell BootROM and does not require any special 
> from
> Bootloader. So you should be able to boot over UART (if you have
> accessible pins).

I know, but there are known versions ob the bootrom where uart boot
isn't supported (correctly). I also have another board which can boot
over uart. But thats in daily use ;)

>> Could you elaborate that a bit more? Why is this required for
>> uart boot? kwboot will talk with the bootrom why does u-boot need
>> anything? Or will there just be no output until the uart is 
>> initialized?
> 
> On mvebu/armada boards this dm-pre-reloc is required to ensure that DT
> nodes are present in SPL DTB file. Otherwise build process drop all
> non-pre-realoc nodes from SPL version of DTB file. And because SPL use
> DM serial, it is required to have uart DT nodes in DTB file. Btw, same
> problem is with SPI in SPL.
> 
> But... kirkwood does not use SPL, so I do not know what is reason for
> this here.

Yes thats what puzzled me, too.

>> >
>> > Signed-off-by: Tony Dinh <mibodhi at gmail.com>
>> > ---
>> >
>> >  arch/arm/dts/kirkwood-u-boot.dtsi | 7 +++++++
>> >  1 file changed, 7 insertions(+)
>> >  create mode 100644 arch/arm/dts/kirkwood-u-boot.dtsi
>> 
>> Is this new? AFAIK only <boardname>-u-boot.dtsi is included
>> automatically.
> 
> It is not new, Tom wrote about it quite ago:
> https://lore.kernel.org/u-boot/20220802121113.GG1146598@bill-the-cat/

Thats relatively new for someone not following the u-boot
development that closely ;) Thanks for the pointer.

-michael