Re: serial console on Mikrotik RB532 non-working

[Waldemar Brodkorb <wbx@openadk.org>]

Hi Jonas,
Jonas Gorski wrote,

> Hi,
> 
> On Tue, Feb 3, 2026 at 7:25 PM Waldemar Brodkorb <wbx@openadk.org> wrote:
> >
> > Hi Jiaxun,
> > Jiaxun Yang wrote,
> > >
> > > On Tue, 3 Feb 2026, at 3:24 PM, Jiaxun Yang wrote:
> > > > On Sun, 1 Feb 2026, at 6:39 PM, Waldemar Brodkorb wrote:
> > > >> Hi MIPS hackers,
> > > >>
> > > >> I want to use the latest Linux kernel on my Mikrotik RB532, but the
> > > >> serial console is non working. I bisected the problem and the first
> > > >> breaking change is this commit:
> > > >
> > > > Hi,
> > > >
> > > > Can you try this?
> > >
> > > Oops sorry I missed a flag, it should be:
> > >
> > > diff --git a/arch/mips/rb532/devices.c b/arch/mips/rb532/devices.c
> > > index 8ecb56be81ac..239018540221 100644
> > > --- a/arch/mips/rb532/devices.c
> > > +++ b/arch/mips/rb532/devices.c
> > > @@ -213,11 +213,12 @@ static struct platform_device rb532_wdt = {
> > >  static struct plat_serial8250_port rb532_uart_res[] = {
> > >         {
> > >                 .type           = PORT_16550A,
> > > -               .membase        = (char *)KSEG1ADDR(REGBASE + UART0BASE),
> > > +               .mapbase        = REGBASE + UART0BASE,
> > > +               .mapsize        = SZ_4K,
> > >                 .irq            = UART0_IRQ,
> > >                 .regshift       = 2,
> > >                 .iotype         = UPIO_MEM,
> > > -               .flags          = UPF_BOOT_AUTOCONF,
> > > +               .flags          = UPF_BOOT_AUTOCONF | UPF_IOREMAP,
> > >         },
> > >         {
> > >                 .flags          = 0,
> > >
> >
> > I tried the patch, but it still hangs here:
> >
> > RouterBOOT booter 2.18
> >
> > RouterBoard 532
> >
> > CPU frequency: 399 MHz
> >   Memory size:  32 MB
> >
> > Press any key within 3 seconds to enter setup...
> > trying dhcp protocol... OK
> > resolved mac address 9C:BF:0D:00:D6:4E
> > Gateway: 192.168.1.254
> > transfer started ........................................ transfer ok, time=525.70s
> > setting up elf image... OK
> > jumping to kernel code
> >
> > Nothing in tcpdump tries to mount nfs, so I believe serial console
> > breakage is not the only problem here.
> 
> Have you tried the patch on top of master or
> 6e690d54cfa802f939cefbd2fa2c91bd0b8bd1b6?
> 
> If it works on top of 6e690d54cfa802f939cefbd2fa2c91bd0b8bd1b6, then
> it fixes the serial issue, and you can do a new git bisect between
> 6e690d54cfa802f939cefbd2fa2c91bd0b8bd1b6 and master to find the next
> breakage, with the patch re-applied on top each step (so serial stays
> working).

Yes, thanks for the idea. I already had this idea in mind and I am 9
steps before I get the next breakage :)

Thanks for the heads up,

 best regards
  Waldemar