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-samsung-soc" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
