Ubuntu
linux package

Regression: No replacement for /proc/acpi/alarm due to missing rtc0

Bug #186297 reported by Martti Kuparinen
12
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Fix Released
Medium
Colin Ian King
Ubuntu hardy-alpha-5

Bug Description

Binary package hint: linux-source-2.6.24

I performed a clean installation of 8.04 and quickly noticed that the ACPI wakeup feature provided by /proc/acpi/alarm in Ubuntu 7.10 (with 2.6.22 kernel) is now deprecated and should be replaced by /sys/class/rtc/rtc0/wakealarm. However, I have nothing in the /sys/class/rtc directory, i.e. rtc0 was not detected.

http://www.mythtv.org/wiki/index.php/ACPI_Wakeup says this:

Warning: The wakealarm interface is incompatible with the kernel's old "Enhanced Real Time Clock Support" and "Generic /dev/rtc emulation" options. If your kernel was built with these enabled your kernel log will contain messages such as

rtc_cmos: probe of 00:03 failed with error -16

The solution is to rebuild your kernel with the above two options excluded (find them under Drivers -> Character Devices) and the various RTC interfaces (found under Drivers -> Real Time Clock) included. From a .config point of view CONFIG_RTC and CONFIG_GEN_RTC must be unset and, at a minimum, RTC_INTF_SYSFS must be set.

I don't see that probe failure on my PC but I have "/build/buildd/linux-2.6.24/drivers/rtc/hctosys.c: unable to open rtc device (rtc0)". Taking a quick look at /boot/config-2.6.24-5-generic shows that I have incorrectly(?) CONFIG_RTC set even though CONFIG_RTC_INTF_SYSFS is also set. I will try to compile my own kernel and see if rtc0 is detected when CONFIG_RTC is unset.

Revision history for this message
Martti Kuparinen (mk1970) wrote :

Linux n71 2.6.24-5-generic #1 SMP Thu Jan 24 19:29:14 UTC 2008 x86_64 GNU/Linux

Revision history for this message
Martti Kuparinen (mk1970) wrote :
Revision history for this message
Martti Kuparinen (mk1970) wrote :
Leann Ogasawara (leannogasawara)
Changed in linux:
assignee: nobody → ubuntu-kernel-team
importance: Undecided → Medium
status: New → Triaged
Revision history for this message
Martti Kuparinen (mk1970) wrote :

Due to some other problems I reinstalled my PC but this time I installed the i386 version (with 2.6.24-5-generic kernel). To my big surprise I have now /proc/acpi/alarm available...

Revision history for this message
Milan Knizek (knizek) wrote :

I can confirm this problem as well on x86_64 ubuntu 8.04 alpha 4 and be glad if it can be resolved, since there is a new hw support (asus wifi dongle, sonyerricson usb mass storage working) in kernel 2.6.24.

Revision history for this message
Colin Ian King (colin-king) wrote :

Indeed, I've checked ubuntu 8.04 alpha 4 on x86_64 and i386. There does seem to be configuration differences wrt the rtc with x86_64 and i386 kernels. Will investigate.

Changed in linux:
assignee: ubuntu-kernel-team → colin-king
status: Triaged → In Progress
Revision history for this message
Colin Ian King (colin-king) wrote :

It appears that drivers/acpi/sleep/proc.c contains the following code:

#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) || !defined(CONFIG_X86)
/* use /sys/class/rtc/rtcX/wakealarm instead; it's not ACPI-specific */
#else
#define HAVE_ACPI_LEGACY_ALARM
#endif

I believe the i386 kernel does not have CONFIG_RTC_DRV_CMOS defined, but the x86_64 version has, hence only the i386 version enables /proc/acpi/alarm.

Colin Ian King (colin-king)
Changed in linux:
status: In Progress → Fix Committed
Colin Ian King (colin-king)
Changed in linux:
status: Fix Committed → In Progress
Colin Ian King (colin-king)
Changed in linux:
status: In Progress → Fix Committed
Revision history for this message
Tim Gardner (timg-tpi) wrote :

commit 572f40c7d44d61dfe48302758fa92440eab81eae in the Hardy tree.
Will appear with 2.6.24-9

Changed in linux:
milestone: none → hardy-alpha-5
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package linux - 2.6.24-9.15

---------------
linux (2.6.24-9.15) hardy; urgency=low

  [Alessio Igor Bogani]

  * rt: Fix FTBS
  * rt: Updated configuration files

  [Tim Gardner]

  * SAUCE: make /dev/kmem a config option
  * SAUCE: x86: introduce /dev/mem restrictions with a config option
  * Fixed CGROUP FTBS caused by AppArmor patch.
  * Enabled CGROUP and CPUSETS for server flavor.
    - LP: #182434

  [Colin King]

  * Turn on /proc/acpi/alarm for x86_64 (amd64)
    - LP: #186297

  [Upstream Kernel Changes]

  * Ubuntu: LatencyTOP infrastructure patch

 -- Tim Gardner <email address hidden> Thu, 14 Feb 2008 13:34:55 -0700

Changed in linux:
status: Fix Committed → Fix Released
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