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hwclock on Raspberry Pi 2 with DS1307 RTC: operates correctly in util-linux 2.30.1, fails in 2.31 #543

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es30 opened this issue Nov 21, 2017 · 8 comments
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hwclock on Raspberry Pi 2 with DS1307 RTC: operates correctly in util-linux 2.30.1, fails in 2.31 #543

es30 opened this issue Nov 21, 2017 · 8 comments

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@es30
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es30 commented Nov 21, 2017

On a Raspberry Pi 2 with DS1307 RTC running Arch Linux ARM with util-linux 2.30.1:

# hwclock -D
hwclock from util-linux 2.30.1
Trying to open: /dev/rtc0
Using the rtc interface to the clock.
Assuming hardware clock is kept in UTC time.
Waiting for clock tick...
/dev/rtc0 does not have interrupt functions. Waiting in loop for time from /dev/rtc0 to change
...got clock tick
Time read from Hardware Clock: 2017/11/21 20:27:03
Hw clock time : 2017/11/21 20:27:03 = 1511296023 seconds since 1969
Time since last adjustment is 1511296023 seconds
Calculated Hardware Clock drift is 0.000000 seconds
2017-11-21 12:27:02.930019-0800
#

But with util-linux 2.31:

# hwclock -D
hwclock from util-linux 2.31
System Time: 1511286992.869143
Trying to open: /dev/rtc0
Using the rtc interface to the clock.
Assuming hardware clock is kept in UTC time.
Waiting for clock tick...
hwclock: ioctl(3, RTC_UIE_ON, 0) to /dev/rtc0 failed: Invalid argument
...synchronization failed
#

Reverting the function synchronize_to_clock_tick_rtc in hwclock-rtc.c to its definition in branch stable/v2.30 restores some semblance of correct operation (which is not to say that this is the fix to the problem):

# ./hwclock -D
hwclock from util-linux 2.31
System Time: 1511287003.907954
Trying to open: /dev/rtc0
Using the rtc interface to the clock.
Assuming hardware clock is kept in UTC time.
Waiting for clock tick...
/dev/rtc0 does not have interrupt functions. ioctl(3, RTC_UIE_ON, 0): Invalid argument
Waiting in loop for time from /dev/rtc0 to change
...got clock tick
Time read from Hardware Clock: 2017/11/21 17:56:45
Hw clock time : 2017/11/21 17:56:45 = 1511287005 seconds since 1969
Time since last adjustment is 1511287005 seconds
Calculated Hardware Clock drift is 0.000000 seconds
2017-11-21 09:56:44.370380-0800
#

For other users experiencing the same problem, see thread https://archlinuxarm.org/forum/viewtopic.php?f=57&t=12222.
@karelzak
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I guess we need

- } else if (errno == ENOTTY) {
+ } else if (errno == ENOTTY || errno == EINVAL) {

@jwpi ?

@es30
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es30 commented Nov 22, 2017

I can't speak to the general case, but the proposed fix works in my particular case:

# ./hwclock -D
hwclock from util-linux 2.31
System Time: 1511366637.637657
Trying to open: /dev/rtc0
Using the rtc interface to the clock.
Assuming hardware clock is kept in UTC time.
Waiting for clock tick...
ioctl(3, RTC_UIE_ON, 0): Invalid argument
Waiting in loop for time from /dev/rtc0 to change
...got clock tick
Time read from Hardware Clock: 2017/11/22 16:03:59
Hw clock time : 2017/11/22 16:03:59 = 1511366639 seconds since 1969
Time since last adjustment is 1511366639 seconds
Calculated Hardware Clock drift is 0.000000 seconds
2017-11-22 08:03:58.097366-08:00
#

@ghost
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ghost commented Nov 22, 2017 via email

@es30
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es30 commented Nov 22, 2017

Hmm, interesting. I would think that my kernel is sufficiently current:

$ uname -a
Linux Corvus 4.9.60-1-ARCH #1 SMP Mon Nov 6 10:03:15 PST 2017 armv7l GNU/Linux

Could the fact that I'm compiling the rtc-ds1307 driver into my kernel be making a difference?

$ diff config config.original
2667c2667
< CONFIG_I2C_BCM2835=y
---
> CONFIG_I2C_BCM2835=m
4606,4607c4606
< CONFIG_RTC_HCTOSYS=y
< CONFIG_RTC_HCTOSYS_DEVICE="rtc0"
---
> # CONFIG_RTC_HCTOSYS is not set
4626c4625
< CONFIG_RTC_DRV_DS1307=y
---
> CONFIG_RTC_DRV_DS1307=m

I'll try running hwclock against the stock kernel with loadable RTC driver, but it will take me a bit of time.

@ghost
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ghost commented Nov 23, 2017 via email

karelzak added a commit that referenced this issue Nov 23, 2017
@karelzak
hwclock: revert ioctl test
800e447 
This commit reverts 1d5cffa.

(I did this revert manually as there was another changes in the code
and git-revert does not work in this case.)

Addresses: #543
Signed-off-by: Karel Zak <kzak@redhat.com>
@karelzak
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The change will in v2.31.1 (probably end of Nov).

@ghost
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ghost commented Dec 13, 2017 via email

@karelzak
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Ah, ... already December. OK, I'l fix it ASAP.

karelzak added a commit that referenced this issue Dec 14, 2017
@karelzak
hwclock: revert ioctl test
32337d9 
This commit reverts 1d5cffa.

(I did this revert manually as there was another changes in the code
and git-revert does not work in this case.)

Addresses: #543
Signed-off-by: Karel Zak <kzak@redhat.com>
@rustybird rustybird mentioned this issue Sep 1, 2018
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