On Wed, Dec 02 2020 at 16:54, Jason Gunthorpe wrote:
> On Wed, Dec 02, 2020 at 08:21:00PM +0100, Thomas Gleixner wrote:
>> So it will not write immediately. It will run through at least one
>> retry.
>
> Right, bascially this is scheduling a WQ to do sched_sync_hw_clock()
> which will only call hrtimer_start() - seems like jsut calling
> hrtimer_start instead of queue_work above would be equivilant
Something like that.
>> I don't think the timer should be canceled if the ntp_synced() state did
>> not change. Otherwise every do_adtimex() call will cancel/restart
>> it, which does not make sense. Lemme stare at it some more.
>
> That makes sense, being conditional on the STA_UNSYNC prior to doing
> any hrtimer_start seems OK?
Yeah.
>> > Also x86 needs a touch, it already has RTC lib, no idea why it also
>> > provides this old path too
>>
>> Because nobody had the stomach and/or cycles to touch it :)
>
> Hahaha yes.. I vaugely remember looking at this once..
>
> Lets see:
>
> arch/x86/kernel/kvmclock.c: x86_platform.set_wallclock =
> kvm_set_wallclock;
> arch/x86/kernel/x86_init.c: x86_platform.set_wallclock =
> set_rtc_noop;
> arch/x86/xen/time.c: x86_platform.set_wallclock =
> xen_set_wallclock;
> arch/x86/xen/time.c: x86_platform.set_wallclock = xen_set_wallclock;
> All returns -ENODEV/EINVAL
You forgot to stare at the .get_wallclock() functions. That's the more
interesting part, i.e. what's behind read_persistent_clock64().
> arch/x86/kernel/x86_init.c: .set_wallclock =
> mach_set_rtc_mmss,
> This is already rtclib under drivers/rtc/rtc-mc146818-lib.c
That's the shared library function for setting the darn thing.
> I suppose the issue here is the rtclib driver only binds via PNP and
> very old x86 systems won't have the PNP tables? It seems doable to
> check for a PNP device after late init and manually create a
> platform_device for the RTC
old crap, broken BIOSes and virt. Welcome to my wonderful world :)
> arch/x86/platform/intel-mid/intel_mid_vrtc.c: x86_platform.set_wallclock =
> vrtc_set_mmss;
> This is also already in rtclib under rtc-mrst.c, and this is already
> wired to create the rtc platform device during init
>
> So it is very close now to be able to delete all this for x86. Do you
> know of something I've missed?
Just the above :)
>> > I wonder if the cmos path could be killed off under the dead HW
>> > principle?
>>
>> Unfortunately that code path is not that dead on x86. You need to fix
>> all the (ab)users first. :)
>
> Assuming x86 can be resolved as above, that leaves two 20 year old MIPS
> platforms and the PPC list from before. ARM is gone compared to last
> time I looked! Progress :)
Yeah. We're zooming in ....
Thanks,
tglx
