Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 24 Apr 2018 12:51:32 +0200 | Subject | Re: [PATCH] m68k: Fix off-by-one calendar month |
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Hi Alexandre,
On Tue, Apr 24, 2018 at 12:37 PM, Alexandre Belloni <alexandre.belloni@bootlin.com> wrote: > On 24/04/2018 12:06:30+0200, Geert Uytterhoeven wrote: >> On Mon, Apr 23, 2018 at 3:02 AM, Finn Thain <fthain@telegraphics.com.au> wrote: >> > This fixes a bug in read_persistent_clock() which causes the system >> > clock to lag the Real Time Clock by one month. The problem was noticed >> > on a Mac, but theoretically it must also affect Atari, BVME6000 and Q40. >> > >> > The tm_mon value in the struct rtc_time passed to mach_hwclk() is >> > zero-based, and atari_mste_hwclk(), atari_tt_hwclk(), bvme6000_hwclk(), >> > mac_hwclk() and q40_hwclk() all make this adjustment. Unfortunately, >> > dn_dummy_hwclk(), mvme147_hwclk(), mvme16x_hwclk(), sun3_hwclk() and >> > sun3x_hwclk() fail to decrement tm_mon. >> > >> > Bring these platforms into line and fix read_persistent_clock() so it >> > works correctly on all m68k platforms. >> > >> > The datasheets for the RTC devices found on the affected platforms >> > all confirm that the year is stored as a value in the range 0-99 and >> > the month is stored as a value in the range 1-12. Please refer to the >> > datasheets for MC146818 (Apollo), DS1643 (MVME), ICM7170 (Sun 3) >> > and M48T02 (Sun 3x). >> > >> > Reported-by: Stan Johnson <userm57@yahoo.com> >> > Signed-off-by: Finn Thain <fthain@telegraphics.com.au> >> >> Thanks, applied and queued for v4.18. >> >> <snip> >> >> > --- a/arch/m68k/kernel/time.c >> > +++ b/arch/m68k/kernel/time.c >> > @@ -74,17 +74,17 @@ static irqreturn_t timer_interrupt(int irq, void *dummy) >> > void read_persistent_clock(struct timespec *ts) >> > { >> > struct rtc_time time; >> > + >> > ts->tv_sec = 0; >> > ts->tv_nsec = 0; >> > >> > - if (mach_hwclk) { >> > - mach_hwclk(0, &time); >> > + if (!mach_hwclk) >> > + return; >> > + >> > + mach_hwclk(0, &time); >> > >> > - if ((time.tm_year += 1900) < 1970) >> > - time.tm_year += 100; > > Note that this change may break existing users. I'm perfectly fine with > it as doing this is generally wrong anyway and this is something I'd > like to see eliminated.
The year handling is moved into the various mach_hwclk() implementations in the same patch (in the "<snip>" part).
> >> > - ts->tv_sec = mktime(time.tm_year, time.tm_mon, time.tm_mday, >> > - time.tm_hour, time.tm_min, time.tm_sec); >> > - } >> > + ts->tv_sec = mktime(time.tm_year + 1900, time.tm_mon + 1, time.tm_mday, >> > + time.tm_hour, time.tm_min, time.tm_sec); >> >> That might explain why my Amiga spends so much time on file system checks >> since I wrote the rp5c01 RTC driver...
Upon closer look, it's not, as Amiga no longer provides mach_hwclk(). So it must be due to fsck running before the rtc module is loaded?
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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