2.6.26-sabayon kernel cannot access hardware clock [Solved]

[Fitzcarraldo]

I have just built the 2.6.26 kernel for x86_64 arch by merging linux-sabayon-2.6.26 and using genkernel, and now SL cannot access my laptop's hardware clock.

The 2.6.25-sabayon-r1 kernel for x86_64 allows the hardware clock to be accessed. The 2.6.26-sabayon kernel for x86_64 does not:

----------What happens with 2.6.25-sabayon-r1 kernel----------
# hwclock
Wed 20 Aug 2008 00:49:19 BST -0.130310 seconds
# uname -a
Linux localhost 2.6.25-sabayon-r1 #1 SMP Tue Jul 1 18:25:45 BST 2008 x86_64 Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz GenuineIntel GNU/Linux
#

----------What happens with 2.6.26-sabayon kernel----------
# hwclock
Cannot access the Hardware Clock via any known method.
Use the --debug option to see the details of our search for an access method.
# hwclock --debug
hwclock from util-linux-ng 2.14
hwclock: Open of /dev/rtc failed, errno=2: No such file or directory.
No usable clock interface found.
Cannot access the Hardware Clock via any known method.
# uname -a
Linux localhost 2.6.26-sabayon #1 SMP Tue Aug 19 23:21:16 BST 2008 x86_64 Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz GenuineIntel GNU/Linux
#

Needless to say, the hardware clock cannot be accessed during booting, and the system clock time cannot be written to the hardware clock during shutdown.

I've filed SL Bugzilla Bug Report No. 503 for this.

[joost]

Code: Select all

xbox-360 joost # hwclock
Wed 20 Aug 2008 08:59:49 AM UTC  -0.309331 seconds
xbox-360 joost # uname -a
Linux xbox-360 2.6.26-sabayon #1 SMP Sat Aug 9 12:00:55 UTC 2008 i686 Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz GenuineIntel GNU/Linux


No problems with the .26 entropy stock kernel.

[Thev00d00]

Code: Select all

b0x v00d00 # hwclock
Cannot access the Hardware Clock via any known method.
Use the --debug option to see the details of our search for an access method.
b0x v00d00 # hwclock --debug
hwclock from util-linux-ng 2.14
hwclock: Open of /dev/rtc failed, errno=2: No such file or directory.
No usable clock interface found.
Cannot access the Hardware Clock via any known method.
b0x v00d00 # uname -a
Linux b0x 2.6.26-sabayon #1 SMP Mon Jul 28 15:16:43 UTC 2008 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 4200+ AuthenticAMD GNU/Linux


Same here, also emerged my kernel and am on x86-64

[Fitzcarraldo]

I'm almost certain it's a bug in the config of the RTC (real time clock) in the kernel configuration file in the linux-sabayon-2.6.26 package, at least for x86_64.

There was also a problem with the RTC in the kernel configuration file in the linux-sabayon-2.6.25 package (see SL Bugzilla Report No. 411 that I filed a while back).

[Fitzcarraldo]

Just found out that if I modprobe the rtc_cmos module then I can access the hardware clock:

Code: Select all

# modprobe rtc_cmos
# hwclock
Sat 23 Aug 2008 01:47:39 BST  -1.006770 seconds
#

So why isn't the rtc_cmos module loaded automatically after building the 2.6.26-sabayon kernel for x86_64? Apparently it was with the 2.6.25-r1 kernel as there is no trouble accessing the hardware clock at boot and shutdown with that kernel.

[Fitzcarraldo]

OK, here's how I fixed the problem (which is due to the way linux-sabayon-2.6.26 configures the kernel).

1. Deselect Real Time Clock:

Device Drivers --->
< > Real Time Clock --->

2. Select CONFIG_RTC, CONFIG_GEN_RTC and CONFIG_GEN_RTC_X (not sure if the last of these is necessary):

Device Drivers --->
Character Devices --->
<M> Enhanced Real Time Clock Support (legacy PC RTC driver)
<M> Generic /dev/rtc emulation
[*] Extended RTC operation

[wolfden]

I'll pass this along to our beloved devs

Thanks for info!

[Fitzcarraldo]

I've found another way of solving the problem. Instead of doing what I wrote in my previous post, build the rtc_cmos driver into the kernel instead of a module.

I.e. instead of the way it is in the .config file created by linux-sabayon-2.6.26:

Device Drivers --->
Real Time Clock --->
<M> PC_style 'CMOS'

do the following instead when you build the kernel:

Device Drivers --->
Real Time Clock --->
<*> PC_style 'CMOS'

[chickpea]

Fitz:

You are quickly becomming one of my favorite people on this earth as you consistently have the same problems I am and consistently fix them before I do.

The modprobe rtc-cmos worked for me too, only I recompiled the kernel and it didn't seem to help. I will post back with relevant info after I recompile my kernel again just to see if doing Real Time Clock as "M" and PC-style CMOS as "Y" makes any difference.

[Fitzcarraldo]

Glad that my travails help others avoid the same. I try to post my solutions to problems to help others but also as a kind of note for myself in case I need it in future.

Let us know if you managed to sort it out on your PC too.