[PATCH 1/2] _PPC frequency change issues - freq already lowered byBIOS

[Thomas Renninger]

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
machines.

Could someone please review and apply.

     Thomas
Author: Thomas Renninger <trenn@xxxxxxx>

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);
 
 	up(&data->lock);