At Wed, 21 Nov 2012 15:15:09 +0100, Tomas Pospisek wrote:
On Tue, 20 Nov 2012 10:01:18 +0100, Takashi Iwai tiwai@suse.de wrote:
At Tue, 20 Nov 2012 09:56:19 +0100, David Henningsson wrote:
On 11/20/2012 09:32 AM, Takashi Iwai wrote:
At Tue, 20 Nov 2012 09:07:21 +0100, David Henningsson wrote:
It does put another question - from where does powertop get its values, and do we have to do anything on our side to make sure / aid them being correct?
powertop checks /sys/class/sound/hwC*D*/power_{off|on}_acct files. They contain the time (in ms) how long the codec is in the power-save mode.
Thanks. But I have also recently seen a computer where powertop showed
a
Watt number, essentially saying that the codec consumed 1.4 Watts or so
(I don't remember the exact number). Have you seen that too?
When 1.4W is constantly consumed even without PCM, it's a bit too high. But with PCM playback, about 1W usage can be measured normally, I guess.
man powertop says:
--calibrate runs powertop in calibration mode. When running on battery, powertop can track power consumption as well as system activity. When there are enough measurements, powertop can start to report power estimates. One can get more accurate estimates by using this option to enable a calibration cycle. This will cycle through various display levesl and USB device activities and workloads.
So that's what powertop does I think: it estimates.
But 100% things from hwC0D0 has nothing to do with the real power usage. It's just the time of HD-audio power-saving mode on and off.
Takashi