After conducting some simplistic tests, I found that the power usage
did not appear to be affected by the CPU frequency.
I tested by playing back a 44.1 KHz FLAC file on single track repeat,
and measured current with the AXP173's battery discharge current ADC.
The button and LCD backlights were set to always on. Headphones were
unplugged and the volume was muted to eliminate any influence from
the headphone amp.
On average the current usage was between 78-81 mA at 1008 MHz, 252 MHz,
and 112 MHz. If anything, 1008 MHz drew _less_ current than the lower
frequencies, by about 1-3 mA.
A possible explanation for this, assuming it's not just a bias of the
test, is that the CPU idle state saves so much power that it's better
to maximize the real time that the CPU spends idling. More systematic
testing is needed to confirm this.
Change-Id: I527473e8c4c12bc1e94f8d4e849fecc108022abe
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