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

[Tony Dinh]

Hi Pali,

On Fri, Feb 3, 2023 at 2:05 PM Pali Rohár <pali at kernel.org> wrote:
>
> On Thursday 02 February 2023 19:04:45 Pali Rohár wrote:
> > On Wednesday 01 February 2023 13:13:16 Tony Dinh wrote:
> > > Hi all,
> > >
> > > On Wed, Feb 1, 2023 at 11:05 AM Pali Rohár <pali at kernel.org> wrote:
> > > >
> > > > On Wednesday 01 February 2023 09:17:15 Michael Walle wrote:
> > > > > > > > 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 heard about it... maybe it is a bug in client software (kwboot)? I do
> > > > not have such board if you are interested in it I could try to send some
> > > > details how to debug it.
> > >
> > > The Kirkwood SoCs came with different BootROM versions. Version 1.1
> > > cannot be booted over UART, but version 1.2  can. I think there must
> > > be a bug in the BootROM 1.1. The older Kirkwood such as Sheevaplug,
> > > Dockstar, iConnect boards come with BootROM 1.1. Later version of
> > > Sheevaplug, GoFlex Home, GoFlex Net, Dreamplug, Pogoplug V4, Zyxel
> > > NSA310S, NSA320, NSA325 come with BootROM 1.2. So even though it is
> > > the same SoC, eg. 6281, they are actually produced at a different time
> > > and have different BootROM versions.
> >
> > There are always multiple revisions of the same SoC. So it is possible
> > that something was broken on first revision of 88F6281 and in next
> > revision was updated BootROM with some fixes. Revision is written on
> > package label and for Armada SoCs it is available also in some register
> > (not sure about Kirkwood). It looks like that there is at least revision
> > Z0 and revision A0 of some Kirkwood SoC.
> >
> > If there is a bug in first revisions then it should be documented in
> > some Kirkwood Errata document. Unfortunately I have never seen it, it is
> > not public, so I have no idea. In any case, if somebody has access to
> > Marvell documents, interesting are these document numbers:
> >
> > * MV-S105223-001 - Differences Between the 88F6192, and 88F6281 Stepping Z0 and A0
> > * MV-S501081-00 - 88F6180, 88F6192, and 88F6281 Functional Errata, Interface Guidelines, and Restrictions
> > * MV-S501157-U0 - 88F6180, 88F6190, 88F6192, and 88F6281 Functional Errata, Interface Guidelines, and Restrictions
> >
> > One of the option how to investigate or debug this issue without
> > documentation is to dump both BootROM versions (1.1, 1.2) and compare
> > them. Either there is different UART protocol for booting (which needs
> > to be implemented) or UART protocol is buggy and needs some workaround
> > or it is completely broken and does not work.
>
> BootROM is mapped to 0xF8000000 address and is 64 kB long. So via U-Boot
> md command it is possible to dump it over console. Or via ext4write
> command store it so ext4 fs on sd card / sata disk.

Thanks for the info. It will be a while before I can get back to this
BootROM 1.1 vs 1.2 topic.

All the best,
Tony