[lkml]   [2006]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 1/2] _PPC frequency change issues
On Dell600/800 machines:

When unplugging the AC adapter on these machines
following happens in BIOS:

- ACPI processor event fired, frequencies get limited
to the lowest one(600 MHz) and BIOS already sets lowest freq.
- when waiting about 10 seconds another ACPI processor event
is fired, and all frequencies are available again,
highest freq(1700 MHz) is set.
- when plugging in ac adapter before waiting 10 seconds
ACPI processor event is happening immediately and all
frequencies are available again, highest freq(1700 MHz) is set.

I found these bugs in kernel:

- speedstep centrino driver does not recognise that BIOS
changed the frequency behind it's back.
It tells you that 600 MHz are already set, and does not invoke
PRE/POST transition validation. On next frequency settings,
the frequency is "out_of_sync" and
the validater assumes 600 MHz and the frequency stays there.

Patch [1/2]

- userspace governor is using its own cpufreq_policy struct and
forgets to set max_frequency there in cpufreq_governor_userspace(CPUFREQ_GOV_LIMITS)
That results in scaling_setspeed staying high in sysfs even the
frequency has been lowered on _PPC change.
When _PPC allows all frequencies again, the userspace governor
uses it's own policy_struct with the old max value again (now the
low one) and the frequency still stays at lowest frequency.
Also the userspace governor need not to hold it's own cpufreq_policy,
better make use of the global core policy, save some memory and
avoid to forget any struct member to be copied.

Patch [2/2]

I tested with ondemand and userspace governor on a speedstep-centrino
system, both governors had problems with but should work fine now,
whether _PPC (or whatever ACPI function) prechanges the freq or not.
The first patch fixes the ondemand governor working properly again,
the second is also needed to make the userspace governor working on these

Could someone please review and apply.

Author: Thomas Renninger <>

BIOS might change frequency behind our back
when BIOS changes allowed frequencies via _PPC.
in this case cpufreq core got out of sync.
-> ask driver for current freq and notify
governors about a change

cpufreq.c | 10 ++++++++++
1 files changed, 10 insertions(+)

Index: linux-2.6.15/drivers/cpufreq/cpufreq.c
--- linux-2.6.15.orig/drivers/cpufreq/cpufreq.c 2006-01-03 04:21:10.000000000 +0100
+++ linux-2.6.15/drivers/cpufreq/cpufreq.c 2006-01-20 11:11:55.000000000 +0100
@@ -1402,6 +1402,16 @@
policy.policy = data->user_policy.policy;
policy.governor = data->user_policy.governor;

+ /* BIOS might change freq behind our back
+ -> ask driver for current freq and notify
+ governors about a change
+ */
+ if (cpufreq_driver->get){
+ policy.cur = cpufreq_driver->get(cpu);
+ if (data->cur != policy.cur)
+ cpufreq_out_of_sync(cpu, data->cur, policy.cur);
+ }
ret = __cpufreq_set_policy(data, &policy);

 \ /
  Last update: 2006-01-24 17:37    [W:0.039 / U:6.640 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site