Again, booting an old kernel leads to working X.
I can confirm that X is not working on a PowerPC G4 Cube with the stock Debian kernel "vmlinux-5.14.0-2-powerpc". X does work with the stock
Debian kernel "vmlinux-5.10.0-8-powerpc". In both cases, I'm using the
latest Debian SID with Xfce. In 5.14.0-2, wdm runs but the system
console screen remains blank (the LCD backlight is on).
(BTW, I have a PowerBook G4 12" 1.5GHz, but I didn't test the 5.14
kernel there. The PB G4 overheats and shuts off whenever it runs
anything CPU-intensive, such as a Gentoo upgrade or even compressing a
file. I think Apple had a way of throttling the CPU speed to prevent overheating -- it doesn't have any problems with Mac OS X Tiger or
Leopard -- but they probably didn't share the details.)
I'll attempt a bisect, starting with mainline v5.14 and going backwards
if necessary (it looks like 5.12.9 worked; I'm not sure about v5.13). If there's a kernel regression, I'll confirm the regression exists on both
the G4 Cube and the PB G4. I don't have an iBook to test.
I can confirm that X is not working on a PowerPC G4 Cube with the
stock
Debian kernel "vmlinux-5.14.0-2-powerpc". X does work with the stock
Debian kernel "vmlinux-5.10.0-8-powerpc". In both cases, I'm using the
latest Debian SID with Xfce. In 5.14.0-2, wdm runs but the system
console screen remains blank (the LCD backlight is on).
(BTW, I have a PowerBook G4 12" 1.5GHz, but I didn't test the 5.14
kernel there. The PB G4 overheats and shuts off whenever it runs
anything CPU-intensive, such as a Gentoo upgrade or even compressing a
file. I think Apple had a way of throttling the CPU speed to prevent overheating -- it doesn't have any problems with Mac OS X Tiger or
Leopard -- but they probably didn't share the details.)
I'll attempt a bisect, starting with mainline v5.14 and going
backwards
if necessary (it looks like 5.12.9 worked; I'm not sure about v5.13).
If
there's a kernel regression, I'll confirm the regression exists on
both
the G4 Cube and the PB G4. I don't have an iBook to test.
On 10/6/21 01:40, Riccardo Mottola wrote:
Again, booting an old kernel leads to working X.Very much sounds like a kernel regression that you should bisect.
That isn't too difficult when cross-building with a fast x86_64 machine.
Adrian
On 10/7/21 06:16, Stan Johnson wrote:
Compiling the downloaded kernel-source using Debian's .config file "config.powerpc_none_powerpc.xz" resulted in a 200 MB kernel (perhaps because it included all possible options), and I couldn't get it to boot (but I also didn't compile or install any modules). But compiling using
the same .config file (see attached) that I've been using for testing
5.13 kernels, and that I also used for the above kernels that worked, results in a working 12 MB kernel, and X is also working:
# uname -a
Linux ppc-cube 5.14.9-pmac #2 SMP Wed Oct 6 21:38:58 MDT 2021 ppc GNU/Linux # ls -l vmlinux
-rwxr-xr-x 1 root root 12382136 Oct 6 15:39 vmlinux
So I think the problem with the default kernel in Debian SID (5.14.0-2)
has already been fixed, or perhaps there was an issue with the options
that were selected for the .config file. Either way, it doesn't appear
that a bisect is needed.
Well, we still have the Debian stock kernel not working. So we might be missing a kernel option that is required for X to work on the PowerMacs.
Did you try building a custom kernel with the config file located in the /boot directory?
Adrian
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - glaubitz@debian.org
`. `' Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
Did you see the error I am getting about BIOS ROM at boot? Do you get it too?
FYI, There are nine powerpc-specific changes in 5.13. It may make
sense to start rolling back those commits first: https://kernelnewbies.org/Linux_5.13#POWERPC
Compiling the downloaded kernel-source using Debian's .config file "config.powerpc_none_powerpc.xz" resulted in a 200 MB kernel (perhaps
because it included all possible options), and I couldn't get it to boot
(but I also didn't compile or install any modules). But compiling using
the same .config file (see attached) that I've been using for testing
5.13 kernels, and that I also used for the above kernels that worked,
results in a working 12 MB kernel, and X is also working:
# uname -a
Linux ppc-cube 5.14.9-pmac #2 SMP Wed Oct 6 21:38:58 MDT 2021 ppc GNU/Linux
# ls -l vmlinux
-rwxr-xr-x 1 root root 12382136 Oct 6 15:39 vmlinux
So I think the problem with the default kernel in Debian SID (5.14.0-2)
has already been fixed, or perhaps there was an issue with the options
that were selected for the .config file. Either way, it doesn't appear
that a bisect is needed.
Well, we still have the Debian stock kernel not working. So we might be
missing a kernel option that is required for X to work on the PowerMacs.
This one ?
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=790690
I may be doing something wrong, but I don't see where. If I'm not doing something wrong, then there could be a problem with the powerpc Debian
config file for 5.14.9.
Compiling 5.14.9 using Debian's 5.14.0-2 config file:
$ rm -r linux-source-5.14
$ xzcat ../linux-source-5.14.tar.xz | tar xf -
$ cd linux-source-5.14
$ cp ../config-5.14.0-2-powerpc .config
$ make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- -j4 clean
olddefconfig vmlinux
...
$ ls -l vmlinux
-rwxr-xr-x 1 johnson johnson 208626696 Oct 8 09:03 vmlinux
$ strings vmlinux | fgrep 'Linux version'
Linux version 5.14.9 (johnson@ThinkPad) (powerpc-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.37) #1 Fri
Oct 8 08:54:06 MDT 2021
The kernel (with modules) is too big to test unless I re-partition the
disk on my G4 Cube.
thanks, stripping vmlinux was the step I was missing.
Starting with the kernel source linux-source-5.14.tar.xz installed from "apt-get install linux-source",
Test 1) Compile using config-5.14.0-2
X fails as before; everything else seems to work. This confirms the
problem with the Debian stock kernel vmlinux-5.14.0-2-powerpc.
Test 2) Compile using config-5.10.0-8
Since the Debian default kernel vmlinux-5.10.0-8-powerpc works, I
expected compiling using config-5.10.0-8 would also work, but the kernel fails while mounting filesystems with these errors, after successfully checking the rootfs:
ext4: Unknown symbol utf8_strncasecmp_folded (err -2)
ext4: Unknown symbol utf8_load (err -r)
ext4: Unknown symbol utf8_casefold (err -2)
ext4: Unknown symbol utf8_strncasecup (err -2)
ext4: Unknown symbol utf8_validate (err -2)
ext4: Unknown symbol utf8_unload (err -2)
At this point, the system drops to a busybox shell.
Here's a diff of config-5.10.0-8-powerpc and config-5.14.0-2-powerpc,
after stripping out the comments:
$ fgrep -v \# config-5.10.0-8-powerpc > t1
$ fgrep -v \# config-5.14.0-2-powerpc > t2
Hello Riccardo!
On 10/7/21 03:39, Riccardo Mottola wrote:
Did you see the error I am getting about BIOS ROM at boot? Do you
get it
too?
This isn't an error, it's just what you expect on a non-x86 system.
Graphics cards having a built-in BIOS is mostly a PC thing and the
BIOS code
on these cards is x86, so these cannot be run on PowerPC machines
anyway.
The purpose of these BIOS ROMs is to provide VESA video modes but
these aren't
used when using a native Linux driver. There used to be an x86
emulator in
XFree86
that would allow executing these ROMs on non-x86 machines. But that
is long in
the past.
So, please just ignore this error message. It's completely harmless
and
unrelated.
I tested these kernels from mainline Linux on the Cube:
5.14.0 works
5.15.0-rc3 works
5.15.0-rc4-00019-g5af4055fa813 works
Kernel 5.14.9 from www.kernel.org also works.
Running "apt-get install kernel-source" downloads:
"linux-source-5.14 (5.14.9-2)".
Compiling the downloaded kernel-source using Debian's .config file "config.powerpc_none_powerpc.xz" resulted in a 200 MB kernel (perhaps
because it included all possible options), and I couldn't get it to
boot
(but I also didn't compile or install any modules). But compiling
using
the same .config file (see attached) that I've been using for testing
5.13 kernels, and that I also used for the above kernels that worked,
results in a working 12 MB kernel, and X is also working:
# uname -a
Linux ppc-cube 5.14.9-pmac #2 SMP Wed Oct 6 21:38:58 MDT 2021 ppc
GNU/Linux
# ls -l vmlinux
-rwxr-xr-x 1 root root 12382136 Oct 6 15:39 vmlinux
So I think the problem with the default kernel in Debian SID
(5.14.0-2)
has already been fixed, or perhaps there was an issue with the options
that were selected for the .config file. Either way, it doesn't appear
that a bisect is needed.
On Nov 6, 2021, at 3:19 PM, Stan Johnson <userm57@yahoo.com> wrote:
Kernel developers have found the bug in the "bad commit" that was
identified above. Details can be found in the
linuxppc-dev@lists.ozlabs.org mailing list.
Since I'm not a kernel developer, I have no idea when the bug correction
will be implemented, but it will probably happen by the time 5.16 is released. In the meantime, a workaround is to set "CONFIG_USER_NS=n" in
the kernel .config file if X is not working on your G4 system.
an update on this - Last kernel 5.15 works fine on my PowerBook again!
Will test now on my iBooks and also on the iMac where I never had issues however.
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