Comment # 20 on bug 944659 from Takashi Iwai

(In reply to milan zimmermann from comment #17)
> I tested with nomodeset making sure to mkconfig and that it appears in
> /boot/grub2/grub.cfg. It did not help, failed to boot 5 times in 6 tries. In
> the succesful boot, the screen resolution was lower, the display narrower
> and stretched, all indications that the nomodeset did kick in.
> 
> But interestingly, in dmesg with the nomodeset, there is an error:
> 
> [    3.167331] pata_jmicron 0000:05:00.1: enabling device (0000 -> 0001)
> [    3.167740] [drm] VGACON disable radeon kernel modesetting.
> [    3.167758] [drm:radeon_init [radeon]] *ERROR* No UMS support in radeon
> module!

This is OK, the expected result.

> I am attaching the full dmesg.
> 
> Overall, from some 1000 boots or so I did during the last week, the only
> reliably working setting was when I boot using USB and in F5 (Kernel), set
> "No ACPI" . But setting acpi=off in the bootloader does not have the same
> effect as I noted.

ACPI=off supposedly disables some devices indirectly, so this might help
avoiding the bad point.

> Not sure where to take it next, but thanks very much for your help so far.
> 
> BTW, Would you have some idea how to find what actual setting is set when I
> select "No ACPI" in the USB boot in F5 (Kernel)?

You can take a look at /proc/cmdline.

Judging from the boot screen you attached in comment 16, this doesn't seem like
a crash of any driver.  Now I read through the kernel log, the possible hit
after the last dying message is acpi-cpufreq.

Could you try to blacklist it, e.g. adding the following line to
/etc/modprobe.d/99-local.conf?

blacklist acpi-cpufreq

Then reboot and retest.  Check dmesg output to verify whether acpi-cpufreq  If
a message with "acpi-cpufreq" appears, the blacklist didn't work -- as a
temporary test, just remove the module from
/lib/modules/$VERSION/kernel/drivers/cpufreq directory.