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

[Tony Dinh]

Hi Stefan,

On Wed, Feb 8, 2023 at 11:15 PM Stefan Roese <sr at denx.de> wrote:
>
> Hi Tony,
>
> On 2/9/23 04:17, Tony Dinh wrote:
> > Hi Stefan,
> >
> > On Fri, Feb 3, 2023 at 4:11 PM Tony Dinh <mibodhi at gmail.com> wrote:
> >>
> >> 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.
> >>
> >
> > I  have run some more tests, and am quite positive that if the uart0
> > node exists in the DTS, it must be tagged with dm,pre-reloc. That is
> > consistent with the serial documentation in
> > doc/develop/driver-model/serial-howto.rst. The issue is whether the
> > uart0 node is specified in the DTS. If it is, the dm-pre-reloc tag
> > must also be used.
> >
> > To prove my theory, I've modified the Pogo V4 DTS to look exactly like
> > the NSA310S, as far as uart0 is concerned. The NSA310S does not even
> > have a uart0 node! and DM_SERIAL boots fine with this box. With the
> > patch below, the Pogo V4 can be kwboot and run normally. No
> > dm-pre-reloc tag is needed.
> >
> > diff --git a/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > b/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > index 5aa4669ae2..227d5ff802 100644
> > --- a/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > +++ b/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > @@ -24,7 +24,8 @@
> >          };
> >
> >          chosen {
> > -               stdout-path = "uart0:115200n8";
> > +               bootargs = "console=ttyS0,115200";
> > +               stdout-path = &uart0;
> >          };
> >
> >          gpio_keys {
> > @@ -97,10 +98,6 @@
> >          };
> >   };
> >
> > -&uart0 {
> > -       status = "okay";
> > -};
> > -
> >   /*
> >    * This PCIE controller has a USB 3.0 XHCI controller at 1,0
> >    */
>
> FWIU, you are hitting a bug in the early serial console code, perhaps
> in serial_check_stdout()?

Quite possible. But I recall trying the same stdout path as the
NSA310S, i.e. stdout-path = &uart0. So the stdout-path itself is not
the reason. Perhaps the bug is in another part of the function.

>
> Could you please check if Pogo V4 boots with
> CONFIG_REQUIRE_SERIAL_CONSOLE unset?
>
Indeed, you're right! unset CONFIG_REQUIRE_SERIAL_CONSOLE allows the
Pogo V4 to boot OK, without dm-pre-reloc needed. And it booted
normally with kwboot, all serial input/outputs are OK.

> > Also, note that just enabling DEBUG_UART would always make the board
> > frozen when u-boot starts.
>
> This should not be the case of course. Are you sure you've correctly
> configured the DEBUG UART?

I think I did that correctly (we've used that to debug the orion_timer
issue previously). Here is how I've configured it:

+CONFIG_DEBUG_UART_BASE=0xf1012000
+CONFIG_DEBUG_UART_CLOCK=250000000
+CONFIG_DEBUG_UART=y

> > So this was another factor why it took me
> > so long to figure this out :) I've just restored everything and
> > removed the uart0 node from the Pogo V4 DTS like above and it is
> > working.
> >
> > But of course, we don't want to change the Pogo V4 DTS, so I will
> > submit another patch just for the Pogo V4 to add -u-boot.dtsi for this
> > box to enable the dm-pre-reloc tag for uart0.
>
> Understood.

Thanks,
Tony

>
> Thanks,
> Stefan