Boot failure with ppc64 port on iMacs G5

[Michael Ellerman]

John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de> writes:
> Hi Michael,
>
> On Thu, 2024-02-29 at 17:42 +1100, Michael Ellerman wrote:
>> > There seems to be a regression in the kernel which affects PowerPC 970 machines,
>> > i.e. PowerMac G5 CPUs. The issue needs to be bisected and reported upstream.
>> 
>> I have a quad G5 that is booting mainline happily.
>
> it's a really tricky problem because it seems to depend on how the kernel image
> is booted.
>
> It fails when trying to boot the kernel off the installation CD, i.e. like from here:
>
>> https://cdimage.debian.org/cdimage/ports/snapshots/2024-02-25/debian-12.0.0-ppc64-NETINST-1.iso
>
> but the kernel will boot fine when installing in an existing system which was installed
> with an installation CD which uses an older kernel.
>
>> https://cdimage.debian.org/cdimage/ports/snapshots/2023-06-18/debian-12.0.0-ppc64-NETINST-1.iso
>
> I have not really figured out yet what the problem is.

OK.

That second iso boots OK for me in qemu. It boots grub and then the
kernel loads and shows:

  Loading ...
  OF stdout device is: /pci at f0000000/mac-io at c/escc at 13000/ch-a at 13020
  Preparing to boot Linux version 6.3.0-1-powerpc64 (debian-kernel at lists.debian.org) (gcc-12 (Debian 12.3.0-2) 12.3.0, GNU ld (GNU Binutils for Debian) 2.40) #1 SMP Debian 6.3.7-1 (2023-06-12)
  Detected machine type: 0000000000000400
  command line: BOOT_IMAGE=/install/vmlinux --- quiet
  memory layout at init:
    memory_limit : 0000000000000000 (16 MB aligned)
    alloc_bottom : 0000000005e70000
    alloc_top    : 0000000030000000
    alloc_top_hi : 0000000080000000
    rmo_top      : 0000000030000000
    ram_top      : 0000000080000000
  copying OF device tree...
  Building dt strings...
  Building dt structure...
  Device tree strings 0x0000000005e80000 -> 0x0000000005e80560
  Device tree struct  0x0000000005e90000 -> 0x0000000005ea0000
  Quiescing Open Firmware ...
  Booting Linux via __start() @ 0x0000000002000000 ...
  Hello World !
  smp_core99_probe
  smp_core99_bringup_done
  Starting system log daemon: syslogd, klogd.

And eventually starts the installer.

That's using no VGA, so possibly there's something wrong with the video
setup on real hardware:

  $ qemu-system-ppc64 -nographic -vga none -M mac99,via=pmu -smp 1 -m 2G -nic user -drive file=$HOME/debian-12.0.0-ppc64-NETINST-1.2023-06-18.iso,format=raw,media=cdrom -boot d

I'll try and find time to test it on my actual G5 next week when I'm in
the office.

cheers