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Power consumption on ath9k

This section documents our metrics used, results and interesting tidbits of information about power consumption for ath9k. If you haven't already go read the Linux 802.11 power consumption section first.

Measured power consumption

We measure the power by feeding external power to the PCIe with a meter attached. We don't yet have any data that shows system level power at this point. But this should be same as what it extracts from the external power source.

We get the IDLE ASSOCIATED power save numbers as 0.02A.

AR9280 power consumption test results

Device state

L1

ASPM off

PS On, Associated

116mW

365mW

PS On + Ping traffic

232mW

450mW

PS off

1090mW

1090mW

ASPM tweaks

ath9k disables the PLL when in L0s as well as receiver clock when in L1, this is done by using the SerDes. Programming the SerDes must go through the same 288 bit serial shift register as the other analog registers. Hence the 9 writes observed. You can look at the code used here:

  • AR9002: ar9002_hw_configpcipowersave() (or ath9k_hw_configpcipowersave() in older kernels)
  • AR9003: ar9003_hw_configpcipowersave()