On 24/04/2018 12:06:30+0200, Geert Uytterhoeven wrote:
Hi Finn,
On Mon, Apr 23, 2018 at 3:02 AM, Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
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.
- 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...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
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