Re: [Help] Microwatt (Zynqwatt) — Kernel halts after Radix MMU init on booting Linux on Zynq version of Microwatt

[Oliver O'Halloran]

On Fri, Nov 14, 2025 at 9:32 AM Mohammad Amin Nili
<manili.devteam at gmail.com> wrote:
>
> Well, I disabled all the early logs (now bootargs = “” in dts) and modified .config
> so that no earlycon.c gets compiled at all. The followings are the only compiled
> files within the `/derivers/tty/serial`:
>
> serial_base_bus.o, serial_core.o, serial_ctrl.o, serial_port.o, xilinx_uartps.o
>
> Now, I get no outputs during booting procedure which sounds normal, I guess.
> But still no luck getting to the rootfs or anywhere which actually initializes the
> `xilinx_uartps` driver and print something.

It might be reaching the rootfs. Initialising a console doesn't
necessarily mean anything is going to use it. Try adding console=ttyS0
to your command line.

> Also please check shenki’s blogpost’s logs, if you have enough time:
>
> https://shenki.github.io/boot-linux-on-microwatt
>
> Based on the blog post, I think there should be no problem to get the early
> booting logs.

And yet you're having problems...

The series that blog post is based on added a udbg driver for the
potato UART they were using for microwatt development. The udbg driver
itself provides early console output and gets turned into hvc0 by the
hvc_udbg driver later on during boot. In your case you don't have
either of those things so you don't get any output. If you wanted to
do something similar you would need to implement a udbg driver for
your xilinx UART. That shouldn't be too hard to do, but fixing the
earlycon driver so it uses early_ioremap() might also work.