2.6.31 regression: iwlagn power_level no longer works

2.6.31 regression: iwlagn power_level no longer works

[Andy Lutomirski]

On 2.6.30.5, I can echo 1 >/sys/class/net/wlan0/device/power_level, and 
the value changes to 1, my wakeup rate goes way down, and my power 
consumption (as measured by powertop) drops noticeably.

On 2.6.31-rc7, I can still echo 1 to that file, but nothing happens, and 
the value I get if I 'cat power_level' remains at 0.

My kernel configs are as identical as 'make oldconfig' knows how to make 
them.

Any ideas?

Re: 2.6.31 regression: iwlagn power_level no longer works

[Gábor Stefanik]

On Tue, Sep 1, 2009 at 11:26 PM, Andy Lutomirski<luto@mit.edu> wrote:
> On 2.6.30.5, I can echo 1 >/sys/class/net/wlan0/device/power_level, and the
> value changes to 1, my wakeup rate goes way down, and my power consumption
> (as measured by powertop) drops noticeably.
>
> On 2.6.31-rc7, I can still echo 1 to that file, but nothing happens, and the
> value I get if I 'cat power_level' remains at 0.
>
> My kernel configs are as identical as 'make oldconfig' knows how to make
> them.
>
> Any ideas?

Power saving has been disabled temporarily in recent versions, as it
caused too many problems. AFAIK either there is either a modparam to
re-enable it or you can re-enable it using iwconfig (it is simply off
by default). There was talk on the mailing list whether to use a
modparam or iwconfig - I don't remember what the outcome was.

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Re: 2.6.31 regression: iwlagn power_level no longer works

[Andrew Lutomirski]

2009/9/1 Gábor Stefanik <netrolller.3d@gmail.com>:
> On Tue, Sep 1, 2009 at 11:26 PM, Andy Lutomirski<luto@mit.edu> wrote:
>> On 2.6.30.5, I can echo 1 >/sys/class/net/wlan0/device/power_level, and the
>> value changes to 1, my wakeup rate goes way down, and my power consumption
>> (as measured by powertop) drops noticeably.
>>
>> On 2.6.31-rc7, I can still echo 1 to that file, but nothing happens, and the
>> value I get if I 'cat power_level' remains at 0.
>>
>> My kernel configs are as identical as 'make oldconfig' knows how to make
>> them.
>>
>> Any ideas?
>
> Power saving has been disabled temporarily in recent versions, as it
> caused too many problems. AFAIK either there is either a modparam to
> re-enable it or you can re-enable it using iwconfig (it is simply off
> by default). There was talk on the mailing list whether to use a
> modparam or iwconfig - I don't remember what the outcome was.

I can't find it in modinfo on iwlcore, iwlagn, cfg80211, or mac80211.
And iwconfig power <n> fails for all the <n> I tried.

If it's intentionally disabled, shouldn't writes to the file fail?  A
printk explaining what's going on might also be nice.  (I bet I won't
be the only one to report a regression of 2.6.31 is released like
this.)

--Andy

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>
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