Kernel hangs on wandboard (freescale imx6)

[Stéphane Graber]

I've been trying to use the generic kernel with my wandboard (based on a freescale imx6) as it's supposed to be working properly.

Using the Ubuntu generic kernel, I usually get a successful boot very shortly followed by a hang.
The hang is: http://paste.ubuntu.com/6216221
That's when using: vmlinuz-3.11.0-12-generic
dmesg for that kernel: http://paste.ubuntu.com/6216265/

Then I noticed that fedora's 3.11 kernel appears to work fine for me and is reasonably stable (though it lacks aufs and overlayfs which I kind of need since I use the board as a buildd).
The fedora kernel I'm using is: vmlinuz-3.11.0-armv7-x13
dmesg for that kernel: http://paste.ubuntu.com/6216246/

A config diff between the two gives me: http://paste.ubuntu.com/6216233/

I believe the git branch for the fedora kernel is at: http://pkgs.fedoraproject.org/cgit/kernel.git

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1237733

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Stéphane Graber (stgraber)]

There's no chance I can run apport on that machine since it hangs after a few seconds, it's already a miracle I can get a shell to last long enough to run dmesg :)

[Joseph Salisbury (jsalisbury)]

Do you happen to know if there was a previous Ubuntu kernel version that boot fine on this board?

[Stéphane Graber (stgraber)]

That's a good question, I'll try a 3.8 generic kernel to see. AFAIK that's the only other generic armhf kernel that we have around.

[Stéphane Graber (stgraber)]

Just tried the latest 3.8 from raring-proposed. It won't boot at all, not getting a single kernel entry on the serial console.
Now looking for a 3.10 kernel from earlier in the saucy cycle.

[Stéphane Graber (stgraber)]

3.10 seems a bit better, at least the kernel loads and the initrd too, though it appears unable to mount the sdcard and so ends up stuck in the initrd after a bunch of mmc related printk.

So it looks like there's no Ubuntu kernel that works properly on this board.

[Paolo Pisati (p-pisati)]

where does the dtb reside in this case? mmc or flash?

in any case, try updating it with the last one that you can find in /lib/firmware/$kernel-version/device-tree/imx6q-sabrelite.dtb

[Stéphane Graber (stgraber)]

The dtb comes from mmc, I'm currently using one coming from the Ubuntu image for the wandboard linked from their website but I also tried the one from the current upstream kernel without seeing any difference in behaviour.

I didn't try any of those shipped with the 3.11 kernel since the imx6q-wandboard one didn't exist back then (was added to the tree shortly after 3.11 released) but I'll give imx6q-sabrelite.dtb a shot later today.

[Stéphane Graber (stgraber)]

Just did a quick test now, the board won't boot the kernel at all using imx6q-sabrelite.dtb so it must be different enough from the wandboard dtb to confuse the kernel very early on.

[Paolo Pisati (p-pisati)]

can you try this kernel:

http://people.canonical.com/~ppisati/linux-image-3.11.0-13-generic_3.11.0-13.20~imx6wands_armhf.deb

and the most appropriate of those dtbs:

ubuntu@arm:~$ ll /lib/firmware/3.11.0-13-generic/device-tree/*wandboard*
-rw-r--r-- 1 root root 31367 Oct 16 10:30 /lib/firmware/3.11.0-13-generic/device-tree/imx6dl-wandboard.dtb
-rw-r--r-- 1 root root 33006 Oct 16 10:30 /lib/firmware/3.11.0-13-generic/device-tree/imx6q-wandboard.dtb

[Stéphane Graber (stgraber)]

So just to sumarize our IRC discussion. The dtb looks good and works great with the fedora kernel.
The kernel itself boots and gets me past the initrd but hangs randomly a bit later on (around network initialization time).

[Paolo Pisati (p-pisati)]

here is another kernel to test:

http://people.canonical.com/~ppisati/linux-image-3.11.0-13-generic_3.11.0-13.20~imx6wandsfullbspplusfedyopts_armhf.deb

moreover, if it hangs just after initrd, would you mind trying to boot without it? could be a buggy module that is loaded afterwards.

[Stéphane Graber (stgraber)]

Just reporting what I said on IRC, this kernel gives me a pretty similar behaviour to the previous one, that's, it hangs at boot around the time apparmor/networking loads and 1/3 times I get a kernel panic: http://paste.ubuntu.com/6251449/

[Paolo Pisati (p-pisati)]

while it's technically possible to make wandboard work with a saucy kernel, that takes ~40 patches.
On the other hand, T already have enough bits to make that board boots and work fine as a server: for theese reasons, i'm marking this as "won't fix' in S, and propose it for T.

[Stéphane Graber (stgraber)]

Yep, I'm fine with that. I had little hope this would be fixed for S and I wasn't planning on running S for very long on that board anyway, so T is fine for me.