This is RFC. It does not even work for me... it sleeps but it will not

wake up, because SATA wakeup code is missing. Code attached for illustration.
I wonder if this is the right approach? What is right interface to the

drivers?
		Sleepy Linux

		~~~~~~~~~~~~
Copyright 2007 Pavel Machek <pavel@suse.cz>

	  GPLv2
Current Linux versions can enter suspend-to-RAM just fine, but only

can do it on explicit request. But suspend-to-RAM is important, eating

something like 10% of power needed for idle system. Starting suspend

manually is not too convinient; it is not an option on multiuser

machine, and even on single user machine, some things are not easy:
1) Download this big chunk in mozilla, then go to sleep
2) Compile this, then go to sleep
3) You can sleep now, but wake me up in 8:30 with mp3 player
Todays hardware is mostly capable of doing better: with correctly set

up wakeups, machine can sleep and successfully pretend it is not

sleeping -- by waking up whenever something interesting happens. Of

course, it is easier on machines not connected to the network, and on

notebook computers.
Requirements:
0) Working suspend-to-RAM, with kernel being able to bring video back.
1) RTC clock that can wake up system
2) Lid that can wake up a system,

   or keyboard that can wake up system and does not loose keypress

   or special screensaver setup
3) Network card that is either down

   or can wake up system on any packet (and not loose too many packets)
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c

index 9663c2a..0f65aa9 100644

--- a/arch/x86/kernel/process_32.c

+++ b/arch/x86/kernel/process_32.c

@@ -178,6 +178,7 @@ void cpu_idle(void)

 	/* endless idle loop with no priority at all */

 	while (1) {

 		tick_nohz_stop_sched_tick();

+		detect_idle();

 		while (!need_resched()) {

 			void (*idle)(void);
diff --git a/drivers/input/input-polldev.c b/drivers/input/input-polldev.c

index 92b3598..83a8046 100644

--- a/drivers/inpu...
[ message continues ]

very nice approach! It might require smarter hardware to be really

efficient, but the generic ability for Linux to utilize S3 automatically

would _quickly_ drive the creation of smarter hardware i'm sure - so i'd

propose to include this even if it wastes power in some cases.
a quick feature request: could you please make the wake-on-RTC

capability generic and add a CONFIG_DEBUG_SUSPEND_ON_RAM=y config option

(disabled by default) that does a short 1-second suspend-to-RAM sequence

upon bootup? That way we could test s2ram automatically (which is a MUCH

needed feature for automated regression testing and automatic

bisection). In addition, some sort of 'suspend for N seconds' /sys or

/dev/rtc capability would be nice as well.
btw., how far are you from having a working prototype?
	Ingo

--

Hmm, are you sure it is good idea to do this from kernel? I guess this
SCSI/SATA issues stop me just now, but even if I get that to work, it

will be extremely disgusting hack... and it is unclear how to do it

nicely :-(.

									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

i have this low-prio effort to make all self-checks automatically

available via 'make randconfig' as well, for all features that have no

natural exposure during normal bootup. So far we've got rcutorture,

kprobes-check, locking/lockdep-self-test and a handful of others.

External scripts tend to go out of sync and LTP takes way too much time 
as long as the sleep periods are within say 10-20 seconds, and our s2ram

cycle is fast and optimal enough, we could do this with networking

enabled too, without dropping/stalling TCP connections left and right.
(Perhaps if we could notify routers that they should batch packets for N

seconds and we could turn off PHY during that time, it would be even

nicer - is there any such router extension in existence?)
but if it's nothing else but a s2ram debug/stress utility, that alone

would be great too :-)
	Ingo

--

Well, I can give you a three liner, and if it stops working, I'll

treat is as a regression, because userland ABI changed...?
Or you can get about 10 lines of C, no problem, but I do not think
 I expect to stress s2ram way too much ;-).

									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Hi,
This is about setting up properly the wakeup sources which means:
- the wakeup source is really capable of generating wakeups for the

target idle state
- the wakeup source is not actually capable of genrating wakeups from

the target idle state, which can be solved in 2 ways:
	- if the duration of the activity is known, set up an alarm

	  (assuming alarms are proper wakeup sources) so that the

	   system is ready just in time, in a less efficient but more

	   responsive power saving state
	- if the duration of the activity is unknown choose the more

	  efficient amongst the following solutions:
		- go to deep sleep state and periodically wakeup and

		  poll, with a period compatible with the timing

		  of the event source
It might be that some hw doesn't provide deep power saving state for

some devices, but if the only missing feature is the wakeup capability,
These are just few system specific case, but if you start including USB

devices, the situation is going to get quite complicated very soon, if

you explicitly include certain HW devices in your model.
--

Cheers, Igor
Igor Stoppa <igor.stoppa@nokia.com>

(Nokia Multimedia - CP - OSSO / Helsinki, Finland)

--

This is the big crux I see.  You're going to constantly wake up the

machine due to broadcast packets, and spend a lot of power just going in

and out of S3.
	-hpa

--

How many machines care a lot about saving power while they are connected

to an ethernet? Wlan might be more of a problem.
	Regards

		Oliver
--

A lot of them should.  An inordinate amount of machines sit there

burning power for no reason.  You can argue that S3 isn't needed -- that

nohz + C3/C4 + turning off the screen would be enough, and that might be

legit.  Heck, I'm constantly frustrated by every distro upgrade breaking

power management for my monitor.
	-hpa

--

NOHZ + C4 + turn off screen + turn off disk + turn off SATA is still

~8W on thinkpad x60.
S3 is ~1W.
That's quite significant difference.
(But yes, connected-to-ethernet is not most important use scenario.)

								Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Still... if we could get the desktops of the world down anywhere close

to that range when not used, it would be a huge win.
	-hpa

--

Plus, it is probably mandatory if you want EnergyStar logo ...

								Pavel
--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Yep... for the first version, I'll be very happy if it autosleeps when

I'm traveling by bus or something. Working with ethernet plugged in is

quite a distant goal.
(But I guess some cleverness could be done on the router or

something. Automagically converting "interesting" packets into WoL

enabled ones, or...?)

									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

You've just eliminated 90%+ of the available Ethernet infrastructure.
However, there may be Ethernet controllers which can do something smart

with incoming packets, and perhaps more importantly, we can always write

a spec and try to push it to Intel, Broadcom, Realtek and Nvidia.
	-hpa

--

IMHO you are making to many special cases. The system can be "sleepy"

if all devices can be runtime suspended and all CPUs are idle.
	Regards

		Oliver
--

Is there an easy way to tell if all the devices are runtime suspended?
I guess I need to know from atomic context :-(.

									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Do you really want to know whether they are suspended or whether they
Urgh. suspend() must be able to sleep and can fail.
	Regards

		Oliver

--

If they are suspended.
My plan is: let the drivers autosuspend on their own. If I see all of

them are autosuspended, then it looks like great time to put whole
That's ok.
... I also don't need to call any suspend() routines, because all the

drivers are already suspended, right?
And yes, I want device activity to prevent s2ram. If user is burning

CD, machine should not sleep. If user is actively typing, machine

should not sleep. My vision is: screen saver tells kernel keyboard

need not be very responsive, at that point keyboard driver can

autosuspend the keyboard, and if that was the last device, whole

system sleeps.

									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Well, you have a number of devices which cannot do runtime pm.

They can do suspend/resume with the whole system. For them these

operations mean saving/restoring state.

So for these devices implementing autosuspend makes no sense.
In these cases the devices involved should report themselves busy,
We lack a notion of telling devices that they are opened only for

detecting wakeups. Currently a driver has to assume that an opened

device has to be fully functional.
	Regards

		Oliver

--

Yep... Let's call busy/idle detection and save/restore state

"autosuspend" for those devices. It does not save any power, but it

can be viewed as "kind-of-suspend". (No, I do not have this kind of
Yes, we'll need to add some userland interfaces. No, this will not be

easy.
									Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Well, you probably would have to walk through all devices and check

all devices are either suspended or can be suspended. That would mean

struct device has to be extended to show common attributes.
But what's wrong with calling suspend() the conventional way once you've

decided to go into sleepy mode?
This mainly means input devices.
	Regards

		Oliver

--

I'm not sure if it can be done in non-racy way. It is different from

"conventional" suspend(): you can still have userland requests after

this suspend(), and you should abort auto-sleep if you get one. (As

opposed to blocking in system suspend case).

								Pavel
--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

But we are always racing against hardware in these cases.
Strictly speaking you cannot have pure userland request. If no task

is runnable and no timer about to fire any activity will require kernel

activity unless you are doing direct hardware access from user space

which in the generic case precludes suspension anyway.
	Regards

		Oliver

--

Your calculation of cost/benefit will be wrong. A driver will have timeouts

based on the cost of a suspend/resume cycle of that device only.

You'd have to calculate of keeping the whole system awake against that.
	Regards

		Oliver

--

Hmm, right. Driver probably should have chance to autosuspend but tell

the core that whole system probably should not sleep... Hmm....
								Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--

Pretty much, except that "timer device" needs to be runtime suspended,

too... We probably should not sleep if wakeup is scheduled 1 second in

future.
								Pavel

--

(english) http://www.livejournal.com/~pavelmachek

(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

--