[mythtv-users] Real Time Clock Alarm Broken with 2.6.22+ kernel

Michelle Dupuis support at ocg.ca
Fri Sep 7 13:06:08 UTC 2007

I wrote an nvram-wakeup replacement call acpi-wakeup.  It is a bash script
that is command line compatible with nvram-wakeup, but uses the proc acpi
interface and handles epoch data etc.  The acpi path is just a constant you
can change.
It would need a tweak to work for you situation, but your welcome to play
with it.  I can put it on www.generationd.com if you want it.


From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Craig Huff
Sent: Friday, September 07, 2007 8:56 AM
To: mythtv-users at mythtv.org
Subject: [mythtv-users] Real Time Clock Alarm Broken with 2.6.22+ kernel

Hi, all

For your information:

I had done a lot of work to figure out how to get the RTC alarm to work in
FC6 on my system so
MythTV can wake from Suspend-to-disk/Power Off to do mythfilldatabase jobs
and to wake 
in time to record scheduled programs. 

I upgraded everything last week when I needed to move MythTV up to the
latest version to switch
over to SchedulesDirect for collecting TV schedule data.

I posted a message on the atrpms list when I discovered that my system
wasn't waking up anymore 
and found that /proc/acpi/alarm didn't exist.  A kind soul (apparently a
kindred MythTV user) replied
with a pointer to the updated wiki page:
<http://www.mythtv.org/wiki/index.php/ACPI_Wakeup> which 
has had an update about the change the kernel gurus did, changing the path
to the alarm to be
/sys/class/rtc/rtc0/wakealarm.  While they were at it, they changed the
format of the value from the
former, human-readable string to the seconds since the "epoch" (see man-page
regarding "date +%s"). 
Oh, and they changed the code behind it so that to change the alarm you have
to first reset it, which
can be done (amongst other ways) by "echo 0 >
/sys/class/rtc/rtc0/wakealarm".  Finally, don't expect 
the value you get back to equal the value you put in to the alarm unless
your mobo is (in my experience)
the rare bird that REALLY takes the WHOLE alarm setting, including month and
year.  You're more
likely to see "echo 12345 > /sys/class/rtc/rtc0/wakealarm; cat
/sys/class/rtc/rtc0/wakealarm" return 
a value like 87654399899 (made up number on my part).  From googling, it
appears that this will be 
the original value plus a TBD constant that depends on your mobo.  YMMV.


On my system, the code changes behind the new design have broken the alarm
function completely. 
I have tried disabling the hwclock update in /etc/init.d/halt, turned on all
the elements in /proc/acpi/wakeup,
and enabled on the (old technology) APM alarm in the BIOS, all to no avail.

If some kind soul has gotten further with this "improvement" and can give me
any ideas how to fix this, 
short of regressing to a kernel < 2.6.22, I would appreciate it.


P.S. If I forgot to mention some detail of relevance, please remind me to
reply with the appropriate data. 

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