[LPIA Hardy LUM] Disable RTC wake alarm to reduce power in Hibernate - attempt #4 (!)

[Tim Gardner]

Colin Ian King wrote:
> Attempt #4, aligned with comments from rtg, smb and some more from apw.
> 
> https://bugs.launchpad.net/dennis/+bug/337943
> 
> Note: This fix comes in 2 patches, the first is general code tidy up 
> (whitespace/tab indentation, formatting) and removing a whole load of
> warnings and errors from checkpatch.  (Note checkpatch complains about 
> the not using strict_stroul in this patch but this is not available in
> Hardy.)
>  
> The second patch is the fix to reduce power consumption during
> hibernate.
> 
> Bug: LP#337943
> 
> LPIA Hardy Lum
> 
> Add sysfs control to enable or disable RTC Event Enable (RTC_EN) bit
> of port ACPI PM1a_EVT_BLK because the BIOS overlooked this
> functionality on the HP Mini. Disabling this before hibernate saves
> several mAh.
> 
> Note that this extends the existing power management tweaks for this
> particular netbook specific module.
> 
> Attached:
> 
> Patch 1 - code tidy up - remove a whole load of checkpatch warnings
> Patch 2 - fix to reduce power consumption
> 
> 

I assume you'll change Patch 2 if acpi_disable_event(ACPI_EVENT_RTC)
does the job? IRC log included for the list archive:

<mjg59> cking: Wow. That hpmini driver is special.
* cking nods
<cking> ..ultimately a generic solution for ICH7 chipsets should be
looked at for saving power on the wake alarm
<mjg59> cking: Why not just have the kernel call
acpi_disable_event(ACPI_EVENT_RTC) if there's no alarm set?
<cking> mjg59: the driver turns off the power to the wake alarm
mechanism - it's more of a low level ICH7 tweak to save power.
<mjg59> cking: It looks like it's just writing to the PM registers,
which is what acpi_disable_event does
<cking> ..is this dependant on the BIOS doing things right?
<mjg59> No
<kees> Keybuk: you weren't standing in front of a mirror when you said it
* cking goes to look at acpi_disable_event more deeply

rtg
-- 
Tim Gardner tim.gardner at canonical.com