Hi Ingo, On Tue, May 07, 2013 at 08:53:48AM +0200, Ingo Molnar wrote: > > * Feng Tang <feng.t...@intel.com> wrote: > > > > is even worse than that. Machine can stay is s2ram for weeks (for a > > > lot more if it is desktop and you do s2ram for powersaving). Also > > > temperature of CPU varies a lot between active and s2ram states. Is > > > TSC good enough? > > > > Yes, I think it is relatively precise. Per our test, system time backed > > by the S3 non stop TSC only has 1 second drift after 4 days running > > (with mixed running and S3 states). And before using this feature, we've > > seen many time drift problems due to the RTC HW or system FW with our > > platforms. > > Nice result ... > > Is that with NTP running?
No, we haven't tested it with NTP yet. > > Without NTP, the TSC fast-calibration on bootup is not (expected to be) > nearly as precise as the 1:345600 precision you've measured. For the some Atom processor like the Moorestown, Medfield, we use a fast TSC calibration by check the FSB freq and ratio from MSRs. See mrst_calibrate_tsc() in arch/x86/platform/mrst/mrst.c, and the calculated value is precise based on our test. Thanks, Feng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/