battery drains after shutdown

battery drains after shutdown

[Zhang Rui]

Hi, Bryan,

I've got a bug report that battery drains after shutdown.
https://bugzilla.kernel.org/show_bug.cgi?id=47811

The problem is that
1. Battery drains after shutdown
2. setting HWCLOCKACCESS=no in /etc/default/hwclock, which bypasses
the /sbin/hwclock --systohc  operation during shutdown, solves the
issue 
3. setting HWCLOCKACCESS=no, but enable RTC wakeup explicitly, the
battery drains similar power
4. I did a google search and found that there are some pages mentioned
that /sbin/hwclock --systohc may enables RTC wakeup unexpectedly.

So do you have any idea about this problem?

BTW, it would be great if you have an account in bugzilla.kernel.org.

thanks,
rui

Re: battery drains after shutdown

[Bryan Henderson]

I don't know much about power states in general, and I can't think of any
reason that any manipulation of the hardware clock would affect the power
state to which the computer shuts down.  This is probably more of a question
for an expert on shutdown.

I've heard of setting the clock disabling the wakeup, but not setting the
clock enabling wakeup.  I think you can determine whether this is happening,
though, by looking at /proc/driver/rtc contents before and after a
hwclock --systohc.

I do have one comment: doing hwclock --systohc at shutdown is almost always
the wrong thing to do; it is a custom that made sense 20 years ago, but not
today.

-- 
Bryan Henderson                                   San Jose, California

Re: battery drains after shutdown

[François Boisson]

Le 15 Feb 2015 23:36:02 +0000
Bryan Henderson <bryanh@giraffe-data.com> a écrit:

> I've heard of setting the clock disabling the wakeup, but not setting the
> clock enabling wakeup.  I think you can determine whether this is happening,
> though, by looking at /proc/driver/rtc contents before and after a
> hwclock --systohc.

root@portos:/home/francois# cat /proc/driver/rtc 
rtc_time	: 15:17:47
rtc_date	: 2015-02-23
alrm_time	: 17:00:32
alrm_date	: 2015-02-23
alarm_IRQ	: no
alrm_pending	: no
update IRQ enabled	: no
periodic IRQ enabled	: no
periodic IRQ frequency	: 1024
max user IRQ frequency	: 64
24hr		: yes
periodic_IRQ	: no
update_IRQ	: no
HPET_emulated	: yes
BCD		: yes
DST_enable	: no
periodic_freq	: 1024
batt_status	: okay
root@portos:/home/francois# hwclock --systohc
root@portos:/home/francois# cat /proc/driver/rtc 
rtc_time	: 15:17:29
rtc_date	: 2015-02-23
alrm_time	: 17:00:32
alrm_date	: 2015-02-23
alarm_IRQ	: no
alrm_pending	: no
update IRQ enabled	: no
periodic IRQ enabled	: no
periodic IRQ frequency	: 1024
max user IRQ frequency	: 64
24hr		: yes
periodic_IRQ	: no
update_IRQ	: no
HPET_emulated	: yes
BCD		: yes
DST_enable	: no
periodic_freq	: 1024
batt_status	: okay
root@portos:/home/francois# 

except the change in the rtc_time, nothing else.
I check acpitool -e, but no change. 


François Boisson

Re: battery drains after shutdown

[Bryan Henderson]

So it appears the invoking 'hwclock' does not enable the RTC wakeup function,
at least in this experiment.

I have no idea what could be causing the battery drain.

-- 
Bryan Henderson                                   San Jose, California