[ltp] ACPI & APM Confused

[Daniel Jimenez]

Franz Rühmland wrote:
> Well, One killer feature I believe in ACPI is C3 power mode for the CPU.

What is C3?

> I don't think this works in apm. That will probably make the battery 
> last a lot longer. (Don't know how much or if there are any problems 
> with it on the T41:s) Basically, I don't really know... :). Someone, 
> please correct me of I'm wrong.
> 
> To get the buttons to work, fn+f4, the lid and the power button are the 
> only ones I got events for in ACPI, you have to define what the computer 
> should do after getting the events. ('cat /proc/acpi/event' to look at 
> what's happening.) This can be done with acpid.
> (I take it you mean nothing happens when you push the buttons.)
> 
> To suspend to RAM do 'echo -n mem > /sys/power/state' or 'echo -n 3 > 
> /proc/acpi/sleep' depending on kernel version and what you have compiled 
> in.
> 
> To suspend to disk do 'echo -n disk > /sys/power/state' or 'echo -n 4 > 
> /proc/acpi/sleep' instead. You also have to pass 
> resume=/dev/hd$SWAP_PARTITION_GOES_HERE to the kernel at boot to get it 
> to resume from disk.
> 
> I doubt you will have much luck with getting it to resume ok, though.
> For me the USB borks completely and I get neverending messages about it 
> not working to every virtual terminal. I have heard several other people 
>  with this experience too. I don't think the wlan came back up either, 
> but I'm not sure. Also I didn't get any button events after a suspend. 
> Never checked if battery events worked though.

I've heard the same complaints. The other day I did echo -n 3 
/proc/acpi/sleep and the machine went to sleep. When I brought it back 
up nothing worked (no keyboard, mouse, etc). I did get display back 
correctly though. I'm not sure if the machine totally locked, or if it 
was just the mouse and keyboard.

> APM on the other hand has been 100% reliable for me. T41 1400MHz 
> (2373-2FG) Using kernel 2.6.3-gentoo-r1 patched with laptop-mode and 
> using powernowd to handle cpufreq. I get ~3h battery time with a 6 cell 
> battery, backlight turned down, using wlan, laptop-mode and CPU at 
> 600MHz. If anyone know how to increase battery time, please do tell.
> 
> I'm using the Phoenix-bios to hibernate. Just make sure you compile USB 
> drivers (uhci_hcd & ehci_hcd) as modules and unload them at suspend and, 
> of course reload them at resume.  I also unload the ndiswrapper module 
> for the intel 2100 wlan card.
> Closing the lid, Fn+* all works as expected.
> 
> I don't know about the pcmcia or bluetooth, simply because I don't have 
> any devices to test it with.
> 
> I use apmd to detect apm events and have written some scripts to take 
> care of the unloading and loading of modules. I have also scripts to 
> handle toggling of laptop_mode and powernowd settings when I switch 
> between battery and AC.

Thanks, APM sound generally more reliable and I may switch over to it.

-- 
Daniel Jimenez <djimenez[at]pobox[dot]com>
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