El 26 de marzo de 2012 04:37, Yongcong Du <ycdu.vmcore@xxxxxxxxx> escribió: > I sent this email yesterday. I dunno why the list didn't receive. So send > again today > > > On Mon, Mar 26, 2012 at 10:15 AM, Yongcong Du <ycdu.vmcore@xxxxxxxxx>wrote: > >> >> >> ---------- Forwarded message ---------- >> From: Yongcong Du <ycdu.vmcore@xxxxxxxxx> >> Date: Sun, Mar 25, 2012 at 11:53 PM >> Subject: [gsoc2012] cpuidle support >> To: haiku-development@xxxxxxxxxxxxx >> >> >> Dear Haiku development list, >> >> I'm a graduate student from China. I'm interested in embedded software >> development especially lowlevel OS issues, drivers, etc. During my last >> intern job, I implemented Linux cpufreq and cpuidle drivers of one arm SoC >> for one company. IOW my job is focused on the SoC's power efficiency under >> Linux >> >> Per my understanding, Linux power efficiency is improved a lot by the >> following features: cpufreq, tickless and cpuidle. Generally speaking, >> cpufreq is used to change the clock speed of the cpus based on system load >> while cpuidle is used to put cpu into deeper idle stage(for example, C2, C3 >> stage on x86) when idle. >> >> I noticed that haiku has supported something similar as cpufreq: >> >> http://www.freelists.org/post/haiku-development/Intel-Enhanced-Speedstep-Driver >> and I did find the related drivers in >> src/add-ons/kernel/drivers/power/enhanced_speedstep/ >> >> I searched via google and also know haiku has already supported the so >> called "tickless" feature. >> >> I found that cpuidle is missing in haiku. So I'd like to take cpuidle >> framework include some platform's cpuidle driver as my GSoC Haiku project. >> I think this project will benefit haiku in power efficiency and will >> extends my laptop's battery life under haiku(also everyone's laptop users' >> ;)) As for the cpuidle drivers, I may need to handle the complex acpi >> subsystem to get the so called C-State, to put cpu into deep idle etc.. But >> for intel snb, ivb etc.. processors, acpi is not necessary In fact, my >> laptop cpuidle works greatly with the intel_idle driver under linux. >> >> So my plan is to implement cpuidle framework, intel cpu cpuidle driver, >> then acpi cpuidle driver if haiku's acpi support is completed. Here are my >> questions: Is this a project that would be suitable for GSoC? Can we get >> c-state from acpi in haiku? >> >> >>  https://lkml.org/lkml/2010/5/28/36 >> >> Thanks in advance >> >> > That would great! I was working on it but I haven't enought time to keep working, and the laptop I used fried its power supply. > Can we get c-state from acpi in haiku? Yes, at least It worked on my laptop. One of the problems I had when working on this issue, was clock signal. Haiku clock doesn't use hpet timers (is this still true?) and changing cpu clock slow downs system clock too. There are a lot of work already done, It seems a feasible project. My thumb up for this project!