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. Eugeny > > - Dave >
