On Tue, Jun 18, 2013 at 4:32 PM, Daniel Lezcano <[email protected]> wrote: > On 06/18/2013 09:17 AM, Magnus Damm wrote: >> From: Magnus Damm <[email protected]> >> >> Introduce the function tick_device_may_c3stop() that >> ignores the C3STOP flag in case CPUIdle is disabled. >> >> The C3STOP flag tells the system that a clock event >> device may be stopped during deep sleep, but if this >> will happen or not depends on things like if CPUIdle >> is enabled and if a CPUIdle driver is available. >> >> This patch assumes that if CPUIdle is disabled then >> the sleep mode triggering C3STOP will never be entered. >> So by ignoring C3STOP when CPUIdle is disabled then it >> becomes possible to use high resolution timers with only >> per-cpu local timers - regardless if they have the >> C3STOP flag set or not. >> >> Observed on the r8a73a4 SoC that at this point only uses >> ARM architected timers for clock event and clock sources. >> >> Without this patch high resolution timers are run time >> disabled on the r8a73a4 SoC - this regardless of CPUIdle >> is disabled or not. >> >> The less short term fix is to add support for more timers >> on the r8a73a4 SoC, but until CPUIdle support is enabled >> it must be possible to use high resoultion timers without >> additional timers. >> >> I'd like to hear some feedback and also test this on more >> systems before merging the code, see the non-SOB below. > > Do we need a broadcast timer when cpuidle is not compiled in the kernel ?
Yes, if there is no per-cpu timer available. It depends on what the SMP support code for a particular SoC or architecture happen to enable. / magnus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
