(Dapper) kernel 2.6.15.15-686 breaks freq scaling on core duo

[Dave Rosky]

After updating dapper to linux-image-2.6.15-15-686, cpu frequency scaling failed to work. The /sys/devices/system/cpu/cpuX/cpufreq directories were not being created. It turned out that the necessary kernel modules were not being loaded. If I load them manually (speedstep-centrino, cpufreq_xxx, etc.), then frequency scaling works.

It appears this kernel is not detecting the hardware correctly or some similar problem.
Dave

[Dave Rosky (d-rosky)]

I should have mentioned, the system is a Dell Inspiron 9400 with Core duo processor and Intel 945 chipset.
Dave

[Dave Rosky (d-rosky)]

Note: This problem is still present after today's kernel update (2.6.15-15.21 (686), Feb 9, 2006).
Dave

[Ben Collins (ben-collins)]

If the kernel wasn't detecting it, then the modules wouldn't work :)

This appears to be an issue in the powernod init scripts, which probably aren't recognizing the newer chips.

You'll likely need to step through the powernowd init script to see why it is failing to do things. E.g.:

sh -x /etc/init.d/powernowd start

[Dave Rosky (d-rosky)]

OK, I'll look at the powernowd init script and see if there might be a problem there.

The interesting thing, however, is that it works fine when booting a slightly older kernel (with no change to powernowd). Another thing is that if I remove powernowd and install powersaved, the same problem occurs, and once again, it works with the older kernel, but not the recent one.

In any case, I will look at the scripts and let you know if I find anything.
Dave

[Dave Rosky (d-rosky)]

OK, this appears to be a timing problem at boot-up with the init scripts. If I restart powernowd after the system has booted, it loads the modules and scales the cpu. So I tried moving powernowd later in the startup sequence and it worked (S30powernowd instead of the default S20 seemed to work). I'm not sure why because there doesn't seem to be anything critical to powernowd that starts between S20 and S30, but somehow powernowd needs to be delayed a bit in order to start.

HOWEVER, powersaved, which worked find with the previous kernel, doesn't work at all with this kernel, even if I restart it long after boot.

So, powernowd works if placed later in the boot sequence but it only scales CPU0 and not CPU1 (powernowd bug??) and powersaved, which properly scales both cpus, doesn't run at all with the new kernel...
Dave

[Paul Sladen (sladen)]

Hello Dave,

Can you try with the latest Dapper and let me know if you're still seeing problems. There has been a slight jiggle in the boot-order for powernowd so that may have fixed things.

[Ian Chiew (ianc)]

I have identical hardware and can verify that the boot-order problem does go away with kernel 2.6.15-20-686 on a stock installation of Dapper.

The ignored-second-CPU problem is indeed a bug in powernowd. It's been fixed as of the latest upstream version (0.97).

[John Dong (jdong)]

I can confirm:

(1) On a core duo laptop, the second core does not scale with the latest Dapper updates.
(2) Installing powernowd 0.97 does remedy the situation.

[mroth (mrothy)]

Confirming this still exists on my Core Duo laptop with Dapper nightlies. A bump in powernowd seems like a good idea.

[Ioannis (jgiannakas)]

2.6.15-21-686 still breaks frequency scalling in Dothan processor on a Vaio VGN-FJ1S. With the default kernel, 2.6.15-20-386 it works fine. I am running dapper beta 2, kubuntu.

[Daniel Silverstone (dsilvers)]

powernowd (0.97-1ubuntu1) dapper; urgency=low

  * New upstream release, UVF exception granted by mdz
  * freshen policy version and debhelper version as per bdale's upload in
    Debian
  * Closes: launchpad #41432, #34115 and #30984

 -- Daniel Silverstone <email address hidden> Mon, 8 May 2006 17:53:20 +0100

[mroth (mrothy)]

Confirming as fixed: after updating to powernowd 0.97, both processor cores appear to scale properly (and independently).