On Tuesday 24 January 2006 17:35, Thomas Renninger wrote:
> 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.
>
Corrected indentation and a whitespace...
I also heard about weird behaviour on Dell Inspiron 8600 (1.5GHz Centrino) and
a Dell Latitude X1 when (un)plugging AC adapter, they probably have the same
problem.
Author: Thomas Renninger <[email protected]>
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
+++ linux-2.6.15/drivers/cpufreq/cpufreq.c
@@ -1402,6 +1402,16 @@ int cpufreq_update_policy(unsigned int c
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);
-
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