On Thu, Jan 15, 2015 at 10:54 PM, Mason <mpeg.blue@xxxxxxx> wrote: > Hello, > > This is a follow-up to my previous thread. > "How many frequencies would cpufreq optimally like to manage?" > http://thread.gmane.org/gmane.linux.ports.arm.kernel/373669 > > As I originally wrote, I'm running 3.14 on an ARM Cortex-A9 > based SoC (namely Tango4 from Sigma Designs). I'd like to get > some feedback on the cpufreq driver I wrote for that platform. > > I decided to expose only a small subset of frequencies (namely > {999,500,333,111} MHz) because, in my tests, the ondemand gov > chose mostly min and max, and the intermediate frequencies not > so much; so I figured "2 intermediate freqs" is good enough. > (I'm ready to hear otherwise.) How many states are really enough depends on the main workloads running on your system. In a closed system (limited number of applications) you can easily characterise your workloads and see what operating points (OPP = voltage, frequency pair) the system spends most of its time in (CPU_FREQ_STAT_DETAILS) and optimize out the remaining OPPs. In an open-ended system where you don't control what applications will run on the system (e.g. android phone), it is probably a good idea to expose more OPPs while keeping in mind that exposing 50 frequencies is probably overkill (and silly) since you're spending more time reaching the "optimum" OPP. Pick some high-impact ones e.g. ones that allow you to lower your voltage. > I tried to use as much generic framework as possible, but I've > read about the clk framework, and it looks to be an even greater > generalization. Are new platforms encouraged to use that, rather > than provide a cpufreq driver? Does it work when voltage scaling > comes in play? (This SoC doesn't have it, but the next will.) > > I'm also wondering how cpufreq and cpuidle interact? Is one a > subset of the other? Are they orthogonal? These queries have been answered by Krzysztof. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
