From: Finn Thain <fthain@telegraphics.com.au>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-m68k@vger.kernel.org, Mathieu Malaterre <malat@debian.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Meelis Roos <mroos@linux.ee>, LKML <linux-kernel@vger.kernel.org>,
y2038 Mailman List <y2038@lists.linaro.org>,
Paul Mackerras <paulus@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Andreas Schwab <schwab@linux-m68k.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Greg Ungerer <gerg@linux-m68k.org>,
Joshua Thompson <funaho@jurai.org>
Subject: Re: [PATCH 1/3] [v2] powerpc: mac: fix rtc read/write functions
Date: Tue, 10 Jul 2018 11:18:34 +1000 (AEST) [thread overview]
Message-ID: <alpine.LNX.2.21.1807101105130.12@nippy.intranet> (raw)
In-Reply-To: <CAK8P3a29rNtWCcgKeJK57C5CPPi74wc1o1cnPJM=Qe+eMKFYjw@mail.gmail.com>
On Mon, 9 Jul 2018, Arnd Bergmann wrote:
>
> The most likely explanation I have here is that the RTC was indeed set
> to an incorrect date, either because of a depleted battery (not unlikely
> for a ~15 year old box) or because it was previously stored incorrectly.
The PowerMac stores the GMT offset in NVRAM, and this gets used to
initialize timezone_offset.
If timezone_offset was negative and now.tv_sec was zero, I think this
could store a 1969 date in the RTC:
int update_persistent_clock64(struct timespec64 now)
{
struct rtc_time tm;
if (!ppc_md.set_rtc_time)
return -ENODEV;
rtc_time64_to_tm(now.tv_sec + 1 + timezone_offset, &tm);
return ppc_md.set_rtc_time(&tm);
}
But maybe now.tv_sec can be shown to be greater than timezone_offset.
Then, what would happen when the timezone in /etc/localtime disagrees with
the timezone_offset stored in NVRAM (PRAM)?
Besides that, if the battery went flat, what use is a backtrace? Why not
scrap the WARN_ON()?
--
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prev parent reply other threads:[~2018-07-10 1:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180619140229.3615110-1-arnd@arndb.de>
[not found] ` <CA+7wUsyN_gru4rW0y3ZzXzYwhfaA=uHKaOG=z5bprnYq6oVfMg@mail.gmail.com>
2018-07-01 15:47 ` [PATCH 1/3] [v2] powerpc: mac: fix rtc read/write functions Meelis Roos
2018-07-09 21:31 ` Arnd Bergmann
2018-07-10 1:18 ` Finn Thain [this message]
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