Converting to DM SERIAL for Kirkwood boards

[Tony Dinh]

Hi Stefan,

On Wed, Dec 21, 2022 at 1:29 AM Stefan Roese <sr at denx.de> wrote:
>
> Hi Pali,
>
> On 12/20/22 09:07, Pali Rohár wrote:
> > On Tuesday 20 December 2022 07:20:15 Stefan Roese wrote:
> >> Hi Tony,
> >>
> >> On 12/20/22 02:36, Tony Dinh wrote:
> >>> Hi Stefan,
> >>>
> >>> On Mon, Dec 19, 2022 at 4:06 PM Tony Dinh <mibodhi at gmail.com> wrote:
> >>>>
> >>>> Hi Stefan,
> >>>>
> >>>> On Mon, Dec 19, 2022 at 1:22 PM Tony Dinh <mibodhi at gmail.com> wrote:
> >>>>>
> >>>>> Hi Stefan,
> >>>>>
> >>>>> On Sun, Dec 18, 2022 at 11:29 PM Stefan Roese <sr at denx.de> wrote:
> >>>>>>
> >>>>>> Hi Tony,
> >>>>>>
> >>>>>> On 12/19/22 07:17, Stefan Roese wrote:
> >>>>>>
> >>>>>> <snip>
> >>>>>>
> >>>>>>>> git checkout 37bb396669b27aa62fe8bc5eeb6bfde92e09c2d3
> >>>>>>>> Previous HEAD position was 3b44b3fdf2 arm: mvebu: Add support for
> >>>>>>>> programming LD0 and LD1 eFuse
> >>>>>>>> HEAD is now at 37bb396669 timer: orion-timer: Only init timer once
> >>>>>>>>
> >>>>>>>> This is where the Pogo V4 was frozen during boot. Among the Kirkwood
> >>>>>>>> boards that I have and used for testing, it is the only one that has
> >>>>>>>> CONFIG_BOOTSTAGE=y.
> >>>>>>>
> >>>>>>> Thanks for testing and git bi-secting.
> >>>>>>>
> >>>>>>>> Should I create a new post for would like to continue this topic here
> >>>>>>>> in this thread?
> >>>>>>>
> >>>>>>> Let me check, if I can find the root cause and this problem quickly. If
> >>>>>>> not, then we should probably disable CONFIG_BOOTSTAGE on the Pogo v4 for
> >>>>>>> a short while until we've fixed this issue.
> >>>>>>
> >>>>>> I fail to spot the problem with this small commit 37bb396669b27a. I can
> >>>>>> also not reproduce this on my Armada XP board - it uses SPL though, this
> >>>>>> might make a difference.
> >>>>>>
> >>>>>> Could you perhaps apply this attached debug patch and make sure, that
> >>>>>> you have DEBUG_UART enabled in your Pogo v4 config. And boot into the
> >>>>>> resulting image.
> >>>>>
> >>>>> Here is the kwboot log with DEBUG_UART. Note that number 322322 below
> >>>>> is part of the log.
> >>>>>
> >>>>> 322322
> >>>>>
> >>>>> U-Boot 2023.01-rc3-00057-g9bd3d354a1-dirty (Dec 19 2022 - 01:29:21 -0800)
> >>>>> Pogoplug V4
> >>>>>
> >>>>> SoC:   Kirkwood 88F6281_A1
> >>>>> Model: Cloud Engines PogoPlug Series 4
> >>>>> DRAM:  128 MiB
> >>>>> 322322322Core:  19 devices, 15 uclasses, devicetree: separate
> >>>>> NAND:  4
> >>>>>
> >>>>
> >>>> Going a bit further with your debug patch, I've added more prints.
> >>>>
> >>>>    static void orion_timer_init(void *base, enum input_clock_type type)
> >>>>    {
> >>>>           /* Only init the timer once */
> >>>> -       if (early_init_done)
> >>>> +       if (early_init_done) {
> >>>> +               printch('6'); // test-only
> >>>>                   return;
> >>>> +       }
> >>>>
> >>>> And the boot log below shows somehow the early_init_done is already
> >>>> true by the time the orion_timer_init is called. Pretty weird, to say
> >>>> the least!
> >>>>
> >>>> --BEGIN LOG--
> >>>> 3262632626
> >>>>
> >>>> U-Boot 2023.01-rc4-dirty (Dec 19 2022 - 15:35:26 -0800)
> >>>> Pogoplug V4
> >>>>
> >>>> SoC:   Kirkwood 88F6281_A1
> >>>> Model: Cloud Engines PogoPlug Series 4
> >>>> DRAM:  128 MiB
> >>>> 326263262632626Core:  19 devices, 15 uclasses, devicetree: separate
> >>>> NAND:  456
> >>>> --END LOG--
> >>>>
> >>>
> >>> I tried this change in drivers/timer/orion-timer.c and it seems to
> >>> work consistently.
> >>>
> >>> -static bool early_init_done __section(".data") = false;
> >>> +static bool early_init_done = false;
> >>>
> >>> I still can't see why it would make a difference. Why does the
> >>> __section macro not work? does the reallocation timing have anything
> >>> to do with this variable being of the wrong value?
> >>
> >> Hmmm, so we might have a problem with memory being overwritten? You
> >> should perhaps where the sections (especially data) are located and
> >> where the stack etc is located. I suggest to also enable DEBUG in
> >> board_f/c.c to see a bit more of the addresses being used.
> >>
> >> Thanks,
> >> Stefan
> >
> > Maybe similar issue as with mbus or atsha?
> > https://lore.kernel.org/u-boot/20220810124609.5765-1-pali@kernel.org/
> > https://lore.kernel.org/u-boot/20220408143015.23163-2-pali@kernel.org/
> >
> > static variables do not work correctly _before_ u-boot relocation. You
> > should avoid usage global OR static variables in code which may be
> > called before relocation. And on some boards are all global, static and
> > bss variables read-only (those which use execute-in-place, e.g. ppc
> > flash).
>
> Thanks for the input. Frankly, I was always a bit hesitant when using
> early static variables. Also with moving them into the data segment.
> Even though this seems to work on some platforms AFAICT.
>
> I've prepared a patch getting rid of this variable by introducing a
> function instead. Tested successfully on my Armada XP platform.
>
> Tony, could you (and perhaps others as well?) test with this new patch,
> if everything still works as expected?

Sure, I'll be glad to.

Thanks,
Tony

>
> Thanks,
> Stefan