On Thu 2006-12-14 00:56:24, Eugeny S. Mints wrote: > David Brownell wrote: > >On Wednesday 13 December 2006 1:03 pm, Pavel Machek wrote: > >>On Wed 2006-12-13 15:12:07, Eugeny S. Mints wrote: > >>>David Brownell wrote: > >>>>On Tuesday 19 September 2006 11:25 am, Pavel Machek wrote: > >>>>>Could you perhaps provide list of operating points for 770? It would > >>>>>help understanding a bit, I'd say. > >>>>If there was a followup here, I missed it ... > >>>> > >>>>ISTR that it doesn't use (formal) operating points, and that a lot of > >>>>the > >>>>basic SOC power savings (vs powering off the display or wifi) come from > >>>>a > >>>>different kind of mechanism entirely. Namely, a combination of dynamic > >>>>tick with a modified system idle task, which enters one of the OMAP low > >>>>power modes during those long periods between clock ticks or other irqs. > >>>> > >>>>That's one of the standard power saving schemes used on OMAP1 platforms > >>>>with Linux. > >>>sample of reasonable operating points for OMAP1 platforms along with > >>>appropriate patches may be found at > >>>http://dynamicpower.sourceforge.net/dpm-omap.html > > > >That's the old DPM stuff not any of the newer proposals right? > > > >I thought the question was specifically what N770 used. > > > > > >>Okay... so you have system with 4 different cpu speeds. That should be > >>simple enough to get running using cpufreq, no need for complex > >>operating points patches. > > > >And OMAP1 does have cpufreq support. I believe that if I checked it out > >I'd find that it's used on N770, as a good way to kick in low voltage > >operation modes. > > > >... that's in addition to the reduced power idle, which didn't seem to > >fit into the DPM framework in any obvious way. > It fits. Omitting some details DPM allows to map/stick operating point to > tasks. Mapping one of OMAP low power mode operating point to idle task does > the job. That's what I call a hack. Take a look at acpi C1..C3 state on i386. They provide same functionality ("reduced power idle"), but they are implemented in reasonable way and already merged. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
