Date: Wed, 29 Mar 2006 03:45:55 +0200
From: Alessandro Zummo <alessandro.zummo@towertech.it>
To: Matt Mackall <mpm@selenic.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Andi Kleen <ak@muc.de>,
       akpm@osdl.org, torvalds@osdl.org, davem@davemloft.net,
       kkojima@rr.iij4u.or.jp, lethal@linux-sh.org, paulus@samba.org,
       ralf@linux-mips.org, rmk@arm.linux.org.uk, linux-kernel@vger.kernel.org,
       Matthias Urlichs <smurf@debian.org>,
       Harlan Stenn <stenn@whimsy.udel.edu>,
       Bryan Henderson <bryanh@giraffe-data.com>, Adrian Bunk <bunk@stusta.de>,
       LaMont Jones <lamont@debian.org>
Subject: Re: 11 minute RTC update (was Re: Remove RTC UIP)
Message-ID: <20060329034555.11785044@inspiron>
In-Reply-To: <20060329012137.GB3642@waste.org>
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	<20060327190037.GB27030@muc.de>
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	<1143512075.2284.2.camel@localhost.localdomain>
	<20060329000215.683eb2d5@inspiron>
	<20060329000345.GZ3642@waste.org>
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Organization: Tower Technologies
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On Tue, 28 Mar 2006 19:21:37 -0600
Matt Mackall <mpm@selenic.com> wrote:

> > > With existing NTP setups, and the kernel no longer writing to the RTC,
> > > you might have the RTC drift far enough that NTP failed to sync on the
> > > next boot. (Correct me if I'm wrong, of course.)
> > 
> >  That's probably true, I'm not expert on the matter. The new subsystem only
> >  covers platforms that were not covered before (i.e. without external patches),
> >  so that this should not impact users because the NTP update mode
> >  was not working on them.
> > 
> >  The problem might arise when other RTC drivers (i.e. x86) will be converted
> >  and deployed.
> > 
> >  We need a migration plan. Any suggestion? 
> 
> I guess the question then becomes: is existing userspace (ntpd)
> already doing its own updates. If so, we can schedule the feature for
> removal in the near future. If not, it may take quite a bit longer.

 I think it isn't. Ideally ntpd should open /dev/rtcX and write the time,
 but I'm not sure if it belongs to it or if a simple hwclock --systohc /dev/rtcX
 should be used.

 Obviously hwclock needs to be updated to support multiple RTCs.

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Turin, Italy

  http://www.towertech.it

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