Messages in this thread |  | | Date | Mon, 25 Mar 2013 15:53:01 -0700 | | From | John Stultz <> | | Subject | Re: [PATCH] ARM: convert arm/arm64 arch timer to use CLKSRC_OF init |
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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.
> 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.
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.
thanks -john
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