On Monday 25 March 2013, John Stultz wrote: > On 03/25/2013 03:36 PM, Arnd Bergmann wrote: > > On Monday 25 March 2013, Rob Herring wrote: > >> I count integrator-cp, realview, versatile and non-DT VExpress that do > >> this (not surprisingly) and 25 platforms or timer implementations plus > >> arm64 that do sched_clock setup in time_init. What's broken by not > >> moving these earlier? > > timekeeping_init() will leave the persistent_clock_exist variable as "false", > > which is read in rtc_suspend() and timekeeping_inject_sleeptime(). > > Are you mixing up the persistent_clock and sched_clock here? From a > generic stand-point they have different requirements. Ah, sorry about that. I had stumbled over the persistent_clock issue earlier and was confusing the two. > > For all I can tell, you will get a little jitter every time you > > do a suspend in that case. Or perhaps it means the system clock > > will be forwarded by the amount of time spent in suspend twice > > after wakeup, but I'm probably misreading the code for that case. > > No, you shouldn't see timekeeping being incremented twice, we check in > rtc_resume code if the persistent clock is present if so we won't inject > any measured suspend time there. But you're probably right that we're > being a little overly paranoid checking the same value twice. Well, the point is that has_persistent_clock() returns false because it is not yet active when the flag gets set in timekeeping_init(), but when we call read_persistent_clock() in timekeeping_suspend(), it will actually return a non-zero time. > As far as the benefit to the persistent clock: it is just a little > better to use, since we can access it earlier in resume, prior to > interrupts being enabled. So we should see less time error introduced > each suspend. Ok. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
