* Arnd Bergmann <arnd@xxxxxxxx> [151005 04:08]: > On Monday 05 October 2015 03:55:55 Tony Lindgren wrote: > > * Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> [151001 15:16]: > > > On 09/30/2015 04:49 PM, Arnd Bergmann wrote: > > > >On Wednesday 30 September 2015 16:42:21 Arnd Bergmann wrote: > > > >> > > > >>TEGRA folks: the tegra_read_persistent_clock() implementation apparently > > > >>predates the Tegra RTC driver and I wonder if they actually do the > > > >>right thing in combination. Could it be that the wall time forwards > > > >>twice as fast as it should during resume when the RTC driver is loaded? > > > >>Could it be that we can simply remove tegra_read_persistent_clock() > > > >>and the register_persistent_clock() infrastructure? > > > >> > > > > > > > >I found the 'sleeptime_injected' variable now, which takes care of > > > >forwarding the clock by the correct amount. > > > > > > > >I also found the CLOCK_SOURCE_SUSPEND_NONSTOP flag next to it, which > > > >should let us use the counter32k driver to provide the correct > > > >time during suspend without the omap_read_persistent_clock() function. > > > >We should be able to just delete that code. > > > > > > > >If we decide to also delete the tegra_read_persistent_clock() > > > >function, we can remove the registration too. > > > > > > > > > +1 > > > > We could maybe have read_persistent_clock() just check for the > > CLOCK_SOURCE_SUSPEND_NONSTOP flag? > > timekeeping_resume() already ignores the persistent clock values if > the clocksource has this set. Do you mean we should additionally > not call the read_persistent_clock() function at all to safe a > few cycles reading that value? Hmm no I mean if we have CLOCK_SOURCE_SUSPEND_NONSTOP we can automatically make read_persistent_clock() use that if nothing else got registered. > How expensive is the function? Usually the persistent clock is on some interconnect, so it is way slower compared to a local timer. It doubt it makes a difference in timekeeping_resume() though :) Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
