On Mon, 31 May 2010, Arve Hjønnevåg wrote: > On Mon, May 31, 2010 at 2:46 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Mon, 31 May 2010, James Bottomley wrote: > >> > >> For MSM hardware, it looks possible to unify the S and C states by doing > >> suspend to ram from idle but I'm not sure how much work that is. > > > > On ARM, it's not rocket science and we have in tree support for this > > already (OMAP). I have done the same thing on a Samsung part as a > > prove of concept two years ago and it's really easy as the hardware is > > sane. Hint: It's designed for mobile devices :) > > > > We already enter the same power state from idle and suspend on msm. In > the absence of misbehaving apps, the difference in power consumption > is entirely caused by periodic timers in the user-space framework > _and_ kernel. It only takes a few timers triggering per second (I > think 3 if they do no work) to double the average power consumption on > the G1 if the radio is off. We originally added wakelocks because the > hardware we had at the time had much lower power consumption in > suspend then idle, but we still use suspend because it saves power. So how do you differentiate between timers which _should_ fire and those you do not care about ? We have mechanisms in place to defer timers so the wakeups are minimized. If that's not enough we need to revisit. Thanks, tglx
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