DM_SERIAL is broken for Kirkwood boards

[Tony Dinh]

Hi Tom,

On Fri, Jan 27, 2023 at 5:39 AM Tom Rini <trini at konsulko.com> wrote:
>
> On Fri, Jan 27, 2023 at 01:31:06PM +0100, Stefan Roese wrote:
> > Hi Tony,
> >
> > On 1/27/23 07:13, Tony Dinh wrote:
> > > Hi all,
> > >
> > > On Thu, Jan 26, 2023 at 3:38 PM Tony Dinh <mibodhi at gmail.com> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > I ran some tests today (Pogo V4 and NSA310S boards) with the latest
> > > > master branch and saw the same behavior we've seen before. The boards
> > > > hung, and the serial console was silent after kwboot finished
> > > > transferring the u-boot image. I'm running with this DTSI patch below
> > > > (to enable dm-pre-reloc for uart0).
> > > >
> > > > If I deselected DM_SERIAL then both boards booted OK with kwboot.
> > > >
> > > > diff --git a/arch/arm/dts/kirkwood-nsa310s.dts
> > > > b/arch/arm/dts/kirkwood-nsa310s.dts
> > > > index 09ee76c2a2..6c5a991fde 100644
> > > > --- a/arch/arm/dts/kirkwood-nsa310s.dts
> > > > +++ b/arch/arm/dts/kirkwood-nsa310s.dts
> > > > @@ -317,3 +317,8 @@
> > > >   &pcie0 {
> > > >          status = "okay";
> > > >   };
> > > > +
> > > > +&uart0 {
> > > > +        u-boot,dm-pre-reloc;
> > > > +        status = "okay";
> > > > +};
> > > > diff --git a/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > > > b/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > > > index 5aa4669ae2..ef495d69f5 100644
> > > > --- a/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > > > +++ b/arch/arm/dts/kirkwood-pogoplug-series-4.dts
> > > > @@ -98,6 +98,7 @@
> > > >   };
> > > >
> > > >   &uart0 {
> > > > +       u-boot,dm-pre-reloc;
> > > >          status = "okay";
> > > >   };
> > > >
> > > > @Michael, it would be great if you could try with your Buffalo board,
> > > > and see if you will experience the same behavior.
> > >
> > > Looks like this commit was the indirect cause of the problem.
> > >
> > > Convert CONFIG_SYS_NS16550_MEM32 et al to Kconfig
> > > https://github.com/u-boot/u-boot/commit/9591b63531fa5a34698ee7bb3800af6c4ea6ba2f
> > >
> > > -CONFIG_SYS_NS16550=y
> > > +CONFIG_SYS_NS16550_SERIAL=y
> > > +CONFIG_SYS_NS16550_REG_SIZE=-4
> >
> > Thanks for digging into this. Could you perhaps prepare a patch like
> > this:
> >
> > diff --git a/arch/arm/mach-kirkwood/Kconfig b/arch/arm/mach-kirkwood/Kconfig
> > index 45cc9326368c..438f86922310 100644
> > --- a/arch/arm/mach-kirkwood/Kconfig
> > +++ b/arch/arm/mach-kirkwood/Kconfig
> > @@ -15,6 +15,7 @@ config SHEEVA_88SV131
> >  config KIRKWOOD_COMMON
> >         bool
> >         select DM_SERIAL
> > +       select SYS_NS16550_SERIAL
> >
> >  config HAS_CUSTOM_SYS_INIT_SP_ADDR
> >          bool "Use a custom location for the initial stack pointer address"
> > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> > index bb5083201b38..7b575295746b 100644
> > --- a/drivers/serial/Kconfig
> > +++ b/drivers/serial/Kconfig
> > @@ -773,7 +773,7 @@ config SYS_NS16550_REG_SIZE
> >         int "ns16550 register width and endianness"
> >         depends on SYS_NS16550_SERIAL || SPL_SYS_NS16550_SERIAL
> >         range -4 4
> > -       default -4 if ARCH_OMAP2PLUS || ARCH_SUNXI
> > +       default -4 if ARCH_OMAP2PLUS || ARCH_SUNXI || ARCH_KIRKWOOD
> >         default 1
> >         help
> >           Indicates register width and also endianness. If positive,
> > big-endian
> >
> > Does this work for you?
>
> Wait, when do you need serial and what are you select'ing for, exactly?
> The ns16550 driver stuff is indeed a bit of a mess, option wise, but
> SYS_NS16550 and SYS_NS16550_SERIAL are not the same. Are you having
> problems in a stage with, or without DM_SERIAL enabled?

The problem was described in the initial email above.

"I ran some tests today (Pogo V4 and NSA310S boards) with the latest
master branch and saw the same behavior we've seen before. The boards
hung, and the serial console was silent after kwboot finished
transferring the u-boot image. I'm running with this DTSI patch below
(to enable dm-pre-reloc for uart0).
If I deselected DM_SERIAL then both boards booted OK with kwboot."

So the problem is seen with DM_SERIAL enabled, and occurs immediately
when u-boot starts.

If I understand correctly, it looks like we just need to select
SYS_NS16550 then the driver can be found by DM serial uclass. And that
worked!

Stefan patch proposes that we make SYS_NS16550_SERIAL available for
ARCH_KIRKWOOD, but I think there is more change is needed with this
approach because:

drivers/serial/Kconfig
config SYS_NS16550_SERIAL
        bool "NS16550 UART or compatible legacy driver"
        depends on !DM_SERIAL
        select SYS_NS16550

Thanks,
Tony

>
> --
> Tom