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

[Pali Rohár]

On Wednesday 01 February 2023 08:53:55 Michael Walle wrote:
> Hi Tony,
> 
> Am 2023-02-01 02:11, schrieb Tony Dinh:
> > 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).

> 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.

> > 
> > 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/