On 10/09/2014 02:01 PM, valdis.kletni...@vt.edu wrote: > On Thu, 09 Oct 2014 21:28:23 +0300, Ran Shalit said: > >> Does anybody know what is the minimum expected time for sleep period >> with the cpuidle ? > > Both processor dependent and sleep level dependent. There's a certain > amount of latency induced by the hardware waking up. > > Look at /sys/devices/system/cpu/cpu*/cpuidle/state*/latency > Yes, that is correct. the sleep and wakeup time are dependent on the power state we attempt (may or maynot achieve)
I personally toggle an unused pin using padmux register write with weak pull up/down in controlled tests (mostly using disable =1 for states I am not measuring), then capture pinctrl toggles using [1] into a csv for many thousands of iterations then use the conservative values. I usually do this at the slowest frequency to capture the worst case values that i feed into cpuidle_driver.states.exit_latency and appropriate value for target_residency - I usually ignore power_usage as the value is never a constant and depends on quiet a few factors that i cannot discuss in public domain. Here are some helpful links on OMAP specific strategies (these may be a little old, but just search for CPUIDLE latency measure in google) https://lwn.net/Articles/384146/ http://www.omappedia.org/wiki/Power_Management_Device_Latencies_Measurement http://lists.linaro.org/pipermail/linaro-dev/2010-August/000568.html [1] https://www.saleae.com/ -- Regards, Nishanth Menon -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
