Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] rtc: adapt allowed RTC update error | Date | Thu, 03 Dec 2020 22:31:02 +0100 |
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On Thu, Dec 03 2020 at 22:05, Thomas Gleixner wrote: > On Thu, Dec 03 2020 at 12:16, Jason Gunthorpe wrote: > So now we have two options to fix this: > > 1) Use a negative sync_offset for devices which need #1 above > (rtc_cmos & similar) > > That requires setting tsched to t2 - abs(sync_offset) > > 2) Use always a positive sync_offset and a flag which tells > rtc_tv_nsec_ok() whether it needs to add or subtract. > > #1 is good enough. All it takes is a comment at the timer start code why > abs() is required. > > Let me hack that up along with the hrtimer muck.
That comment in rtc.h makes me cry:
/* Number of nsec it takes to set the RTC clock. This influences when * the set ops are called. An offset: * - of 0.5 s will call RTC set for wall clock time 10.0 s at 9.5 s * - of 1.5 s will call RTC set for wall clock time 10.0 s at 8.5 s * - of -0.5 s will call RTC set for wall clock time 10.0 s at 10.5 s */
Setting the wall clock time 10.0 at 10.5 is only possible for time traveling RTCs. It magically works, but come on ...
Thanks,
tglx
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