Re: [Qemu-devel] [RFC PATCH 0/2] hw/char/bcm2835_aux: Provide full 16550 UART support

[Guenter Roeck]

On 8/20/19 8:08 AM, Philippe Mathieu-Daudé wrote:
> On 8/20/19 4:31 PM, Guenter Roeck wrote:
> > On 8/20/19 5:34 AM, Philippe Mathieu-Daudé wrote:
> > > Hi,
> > >
> > > Since there has been some activity on the list asking about
> > > Rasberry PI USB support, I had a look a some previous unfinished
> > > work and rebased it to share, in case it helps hobbyist interested
> > > in improving these machines.
> > >
> > > This series is some proof-of-concept on improving the AUX UART
> > > support. See the commit description for various TODO/questions.
> > >
> > > This can be tested using files documented by Peter Maydell in
> > > his blog post:
> > > https://translatedcode.wordpress.com/2018/04/25/debian-on-qemus-raspberry-pi-3-model/
> > >
> > >
> > > And using the kernel command line arguments suggested by Guenter Roeck:
> > >
> > > qemu-system-aarch64 -M raspi3 -m 1024 \
> > >     -kernel raspi3/bootpart/vmlinuz-4.14.0-3-arm64 \
> > >     -initrd raspi3/bootpart/initrd.img-4.14.0-3-arm64 \
> > >     -dtb raspi3/bootpart/bcm2837-rpi-3-b.dtb \
> > >     -append 'earlycon=uart8250,mmio32,0x3f215040 rdinit=/sbin/init
> > > panic=-1 console=ttyS1,115200' \
> > >     -drive
> > > file=raspi3/2018-01-08-raspberry-pi-3-buster-PREVIEW.img,format=raw,if=sd
> > > \
> > >     -serial null -serial stdio \
> > >     -d unimp,guest_errors -trace bcm283\*
> >
> > [ ... ]
> >
> > > [    3.123313] Unpacking initramfs...
> > >
> > > Here it hangs, even with CPRMAN patch from Guenter:
> > > https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg03153.html
> >
> > This command line works for me:
> >
> > qemu-system-aarch64 -M raspi3 -kernel arch/arm64/boot/Image -no-reboot \
> >      -nographic -snapshot -smp 4 -m 1G \
> >      -drive file=rootfs.ext2,format=raw,if=sd \
> >      -serial null -serial stdio -monitor none -no-reboot \
> >      --append 'panic=-1 slub_debug=FZPUA root=/dev/mmcblk0 rootwait
> > earlycon=uart8250,mmio32,0x3f215040 console=ttyS1,115200' \
> >      -dtb arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dtb
> >
> > or, with initrd:
> >
> > qemu-system-aarch64 -M raspi3 -kernel arch/arm64/boot/Image -no-reboot \
> >      -nographic \
> >      -initrd rootfs.cpio \
> >      -m 1G -serial null -serial stdio -monitor none -no-reboot \
> >      --append 'panic=-1 slub_debug=FZPUA rdinit=/sbin/init
> > earlycon=uart8250,mmio32,0x3f215040 console=ttyS1,115200' \
> >      -dtb arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dtb
> >
> > This is with the mainline kernel.
> >
> > I don't see a significant difference to your patch series.

Sorry, I meant ".. difference to the command line you used
to test your patch series".

> Thank you for taking the time to test!
>
> The biggest difference is the diffstat:
>
>   hw/char/bcm2835_aux.c         | 211 +++-------------------------------
>
> The model is now cleaner and easier to maintain.
>
> The logical differences are noted in 2nd patch, basically:
> 1- not same FIFO length (easily fixable)
> 2- now the model implements more feature than supposed to
> 3- migration
>
> I'll wait for the different ARM/Migration subsystem review.
>
> [...]
> > One possibility might be that your initrd has a problem. Can you boot
> > without your patch
> > series, or is it always stuck ?
>
> I remember it used to work for me back when I wrote it, so it is
> probably an initrd problem. I'll test later and keep you updated.

You could give it a try with the images I use:

https://github.com/groeck/linux-build-test/tree/master/rootfs/arm64

Only caveat is that you'd have to specify "noreboot" as command line
option if you don't want the system to reboot immediately.

Guenter