From: Thomas Gleixner <tglx@linutronix.de>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Miroslav Lichvar <mlichvar@redhat.com>,
linux-kernel@vger.kernel.org,
John Stultz <john.stultz@linaro.org>,
Prarit Bhargava <prarit@redhat.com>
Subject: Re: [PATCH] rtc: adapt allowed RTC update error
Date: Wed, 02 Dec 2020 20:21:00 +0100 [thread overview]
Message-ID: <87a6uwdnfn.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201202162723.GJ5487@ziepe.ca>
On Wed, Dec 02 2020 at 12:27, Jason Gunthorpe wrote:
> On Wed, Dec 02, 2020 at 02:44:53PM +0100, Thomas Gleixner wrote:
>> if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) ||
>> IS_ENABLED(CONFIG_RTC_SYSTOHC))
>> - queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
>> + queue_work(system_power_efficient_wq, &sync_work);
>
> As Miroslav noted, probably the right thing to do here is to reset the
> hrtimer and remove the sync_work? I think this code was to expedite an
> RTC sync when NTP fixes the clock on boot.
This has two purposes:
1) Initiating the update on boot once ntp is synced.
2) Reinitiating the sync after ntp lost sync and the work did not
reschedule itself because it observed !ntp_synced().
In both cases it's highly unlikely that the write actually happens when
the work is queued because do_adjtimex() would have to be exactly around
the valid update window. So it will not write immediately. It will run
through at least one retry.
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.
> IIRC this was made somewhat messy due to the dual path with rtclib and
> old cmos.
:)
> It would be very nice to kill the cmos path, things are better
> now.. But PPC still has a long way to go:
>
> arch/powerpc/platforms/52xx/efika.c: .set_rtc_time = rtas_set_rtc_time,
> arch/powerpc/platforms/8xx/mpc86xads_setup.c: .set_rtc_time = mpc8xx_set_rtc_time,
> arch/powerpc/platforms/8xx/tqm8xx_setup.c: .set_rtc_time = mpc8xx_set_rtc_time,
> arch/powerpc/platforms/cell/setup.c: .set_rtc_time = rtas_set_rtc_time,
> arch/powerpc/platforms/chrp/setup.c: ppc_md.set_rtc_time = rtas_set_rtc_time;
> arch/powerpc/platforms/chrp/setup.c: .set_rtc_time = chrp_set_rtc_time,
> arch/powerpc/platforms/maple/setup.c: .set_rtc_time = maple_set_rtc_time,
> arch/powerpc/platforms/powermac/setup.c: .set_rtc_time = pmac_set_rtc_time,
> arch/powerpc/platforms/pseries/setup.c: .set_rtc_time = rtas_set_rtc_time,
>
> 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 :)
> 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. :)
Thanks,
tglx
next prev parent reply other threads:[~2020-12-02 19:21 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 14:38 [PATCH] rtc: adapt allowed RTC update error Miroslav Lichvar
2020-12-01 16:12 ` Jason Gunthorpe
2020-12-01 17:14 ` Miroslav Lichvar
2020-12-01 17:35 ` Jason Gunthorpe
2020-12-02 10:01 ` [PATCHv2] " Miroslav Lichvar
2020-12-02 13:44 ` [PATCH] " Thomas Gleixner
2020-12-02 15:07 ` Miroslav Lichvar
2020-12-02 15:36 ` Miroslav Lichvar
2020-12-02 18:36 ` Thomas Gleixner
2020-12-02 16:27 ` Jason Gunthorpe
2020-12-02 19:21 ` Thomas Gleixner [this message]
2020-12-02 20:54 ` Jason Gunthorpe
2020-12-02 22:08 ` Thomas Gleixner
2020-12-02 23:03 ` Jason Gunthorpe
2020-12-03 1:14 ` Thomas Gleixner
2020-12-03 2:04 ` Jason Gunthorpe
2020-12-03 2:10 ` Alexandre Belloni
2020-12-03 15:39 ` Thomas Gleixner
2020-12-03 16:16 ` Jason Gunthorpe
2020-12-03 21:05 ` Thomas Gleixner
2020-12-03 21:31 ` Thomas Gleixner
2020-12-03 22:36 ` Jason Gunthorpe
2020-12-04 13:02 ` Thomas Gleixner
2020-12-04 14:08 ` Jason Gunthorpe
2020-12-04 14:37 ` Alexandre Belloni
2020-12-04 14:46 ` Jason Gunthorpe
2020-12-04 15:08 ` Alexandre Belloni
2020-12-04 15:57 ` Jason Gunthorpe
2020-12-04 16:35 ` Alexandre Belloni
2020-12-03 22:00 ` Alexandre Belloni
2020-12-04 9:34 ` Thomas Gleixner
2020-12-04 9:51 ` Alexandre Belloni
2020-12-04 10:44 ` Thomas Gleixner
2020-12-03 17:29 ` Alexandre Belloni
2020-12-03 19:52 ` Thomas Gleixner
2020-12-03 15:52 ` Jason Gunthorpe
2020-12-03 16:07 ` Alexandre Belloni
2020-12-03 20:10 ` Jason Gunthorpe
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