Commit 406e7938 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
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PM / sleep: System sleep state selection interface rework 



There are systems in which the platform doesn't support any special
sleep states, so suspend-to-idle (PM_SUSPEND_FREEZE) is the only
available system sleep state.  However, some user space frameworks
only use the "mem" and (sometimes) "standby" sleep state labels, so
the users of those systems need to modify user space in order to be
able to use system suspend at all and that may be a pain in practice.

Commit 0399d4db (PM / sleep: Introduce command line argument for
sleep state enumeration) attempted to address this problem by adding
a command line argument to change the meaning of the "mem" string in
/sys/power/state to make it trigger suspend-to-idle (instead of
suspend-to-RAM).

However, there also are systems in which the platform does support
special sleep states, but suspend-to-idle is the preferred one anyway
(it even may save more energy than the platform-provided sleep states
in some cases) and the above commit doesn't help in those cases.

For this reason, rework the system sleep state selection interface
again (but preserve backwards compatibiliby).  Namely, add a new
sysfs file, /sys/power/mem_sleep, that will control the system
suspend mode triggered by writing "mem" to /sys/power/state (in
analogy with what /sys/power/disk does for hibernation).  Make it
select suspend-to-RAM ("deep" sleep) by default (if supported) and
fall back to suspend-to-idle ("s2idle") otherwise and add a new
command line argument, mem_sleep_default, allowing that default to
be overridden if need be.

At the same time, drop the relative_sleep_states command line
argument that doesn't make sense any more.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarMario Limonciello <mario.limonciello@dell.com>
parent 62a03def

Documentation/ABI/testing/sysfs-power

+25 −20
Original line number Diff line number Diff line
@@ -7,30 +7,35 @@ Description: 
		subsystem.



What:		/sys/power/state

Date:		May 2014

Date:		November 2016

Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>

Description:

		The /sys/power/state file controls system sleep states.

		Reading from this file returns the available sleep state

		labels, which may be "mem", "standby", "freeze" and "disk"

		(hibernation).  The meanings of the first three labels depend on

		the relative_sleep_states command line argument as follows:

		 1) relative_sleep_states = 1

		    "mem", "standby", "freeze" represent non-hibernation sleep

		    states from the deepest ("mem", always present) to the

		    shallowest ("freeze").  "standby" and "freeze" may or may

		    not be present depending on the capabilities of the

		    platform.  "freeze" can only be present if "standby" is

		    present.

		 2) relative_sleep_states = 0 (default)

		    "mem" - "suspend-to-RAM", present if supported.

		    "standby" - "power-on suspend", present if supported.

		    "freeze" - "suspend-to-idle", always present.



		Writing to this file one of these strings causes the system to

		transition into the corresponding state, if available.  See

		Documentation/power/states.txt for a description of what

		"suspend-to-RAM", "power-on suspend" and "suspend-to-idle" mean.

		labels, which may be "mem" (suspend), "standby" (power-on

		suspend), "freeze" (suspend-to-idle) and "disk" (hibernation).



		Writing one of the above strings to this file causes the system

		to transition into the corresponding state, if available.



		See Documentation/power/states.txt for more information.



What:		/sys/power/mem_sleep

Date:		November 2016

Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>

Description:

		The /sys/power/mem_sleep file controls the operating mode of

		system suspend.  Reading from it returns the available modes

		as "s2idle" (always present), "shallow" and "deep" (present if

		supported).  The mode that will be used on subsequent attempts

		to suspend the system (by writing "mem" to the /sys/power/state

		file described above) is enclosed in square brackets.



		Writing one of the above strings to this file causes the mode

		represented by it to be used on subsequent attempts to suspend

		the system.



		See Documentation/power/states.txt for more information.



What:		/sys/power/disk

Date:		September 2006

Documentation/kernel-parameters.txt

+6 −7
Original line number Diff line number Diff line
@@ -2325,6 +2325,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			memory contents and reserves bad memory

			regions that are detected.



	mem_sleep_default=	[SUSPEND] Default system suspend mode:

			s2idle  - Suspend-To-Idle

			shallow - Power-On Suspend or equivalent (if supported)

			deep    - Suspend-To-RAM or equivalent (if supported)

			See Documentation/power/states.txt.



	meye.*=		[HW] Set MotionEye Camera parameters

			See Documentation/video4linux/meye.txt.
@@ -3668,13 +3674,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			[KNL, SMP] Set scheduler's default relax_domain_level.

			See Documentation/cgroup-v1/cpusets.txt.



	relative_sleep_states=

			[SUSPEND] Use sleep state labeling where the deepest

			state available other than hibernation is always "mem".

			Format: { "0" | "1" }

			0 -- Traditional sleep state labels.

			1 -- Relative sleep state labels.



	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area



	reservetop=	[X86-32]

Documentation/power/states.txt

+38 −22
Original line number Diff line number Diff line
@@ -8,25 +8,41 @@ for each state. 


The states are represented by strings that can be read or written to the

/sys/power/state file.  Those strings may be "mem", "standby", "freeze" and

"disk", where the last one always represents hibernation (Suspend-To-Disk) and

the meaning of the remaining ones depends on the relative_sleep_states command

line argument.



For relative_sleep_states=1, the strings "mem", "standby" and "freeze" label the

available non-hibernation sleep states from the deepest to the shallowest,

respectively.  In that case, "mem" is always present in /sys/power/state,

because there is at least one non-hibernation sleep state in every system.  If

the given system supports two non-hibernation sleep states, "standby" is present

in /sys/power/state in addition to "mem".  If the system supports three

non-hibernation sleep states, "freeze" will be present in /sys/power/state in

addition to "mem" and "standby".



For relative_sleep_states=0, which is the default, the following descriptions

apply.



state:		Suspend-To-Idle

"disk", where the last three always represent Power-On Suspend (if supported),

Suspend-To-Idle and hibernation (Suspend-To-Disk), respectively.



The meaning of the "mem" string is controlled by the /sys/power/mem_sleep file.

It contains strings representing the available modes of system suspend that may

be triggered by writing "mem" to /sys/power/state.  These modes are "s2idle"

(Suspend-To-Idle), "shallow" (Power-On Suspend) and "deep" (Suspend-To-RAM).

The "s2idle" mode is always available, while the other ones are only available

if supported by the platform (if not supported, the strings representing them

are not present in /sys/power/mem_sleep).  The string representing the suspend

mode to be used subsequently is enclosed in square brackets.  Writing one of

the other strings present in /sys/power/mem_sleep to it causes the suspend mode

to be used subsequently to change to the one represented by that string.



Consequently, there are two ways to cause the system to go into the

Suspend-To-Idle sleep state.  The first one is to write "freeze" directly to

/sys/power/state.  The second one is to write "s2idle" to /sys/power/mem_sleep

and then to wrtie "mem" to /sys/power/state.  Similarly, there are two ways

to cause the system to go into the Power-On Suspend sleep state (the strings to

write to the control files in that case are "standby" or "shallow" and "mem",

respectively) if that state is supported by the platform.  In turn, there is

only one way to cause the system to go into the Suspend-To-RAM state (write

"deep" into /sys/power/mem_sleep and "mem" into /sys/power/state).



The default suspend mode (ie. the one to be used without writing anything into

/sys/power/mem_sleep) is either "deep" (if Suspend-To-RAM is supported) or

"s2idle", but it can be overridden by the value of the "mem_sleep_default"

parameter in the kernel command line.



The properties of all of the sleep states are described below.





State:		Suspend-To-Idle

ACPI state:	S0

Label:		"freeze"

Label:		"s2idle" ("freeze")



This state is a generic, pure software, light-weight, system sleep state.

It allows more energy to be saved relative to runtime idle by freezing user
@@ -35,13 +51,13 @@ lower-power than available at run time), such that the processors can 
spend more time in their idle states.



This state can be used for platforms without Power-On Suspend/Suspend-to-RAM

support, or it can be used in addition to Suspend-to-RAM (memory sleep)

to provide reduced resume latency.  It is always supported.

support, or it can be used in addition to Suspend-to-RAM to provide reduced

resume latency.  It is always supported.





State:		Standby / Power-On Suspend

ACPI State:	S1

Label:		"standby"

Label:		"shallow" ("standby")



This state, if supported, offers moderate, though real, power savings, while

providing a relatively low-latency transition back to a working system.  No
@@ -58,7 +74,7 @@ state. 


State:		Suspend-to-RAM

ACPI State:	S3

Label:		"mem"

Label:		"deep"



This state, if supported, offers significant power savings as everything in the

system is put into a low-power state, except for memory, which should be placed

kernel/power/main.c

+85 −3
Original line number Diff line number Diff line
@@ -78,6 +78,78 @@ static ssize_t pm_async_store(struct kobject *kobj, struct kobj_attribute *attr, 


power_attr(pm_async);



#ifdef CONFIG_SUSPEND

static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,

			      char *buf)

{

	char *s = buf;

	suspend_state_t i;



	for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++)

		if (mem_sleep_states[i]) {

			const char *label = mem_sleep_states[i];



			if (mem_sleep_current == i)

				s += sprintf(s, "[%s] ", label);

			else

				s += sprintf(s, "%s ", label);

		}



	/* Convert the last space to a newline if needed. */

	if (s != buf)

		*(s-1) = '\n';



	return (s - buf);

}



static suspend_state_t decode_suspend_state(const char *buf, size_t n)

{

	suspend_state_t state;

	char *p;

	int len;



	p = memchr(buf, '\n', n);

	len = p ? p - buf : n;



	for (state = PM_SUSPEND_MIN; state < PM_SUSPEND_MAX; state++) {

		const char *label = mem_sleep_states[state];



		if (label && len == strlen(label) && !strncmp(buf, label, len))

			return state;

	}



	return PM_SUSPEND_ON;

}



static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr,

			       const char *buf, size_t n)

{

	suspend_state_t state;

	int error;



	error = pm_autosleep_lock();

	if (error)

		return error;



	if (pm_autosleep_state() > PM_SUSPEND_ON) {

		error = -EBUSY;

		goto out;

	}



	state = decode_suspend_state(buf, n);

	if (state < PM_SUSPEND_MAX && state > PM_SUSPEND_ON)

		mem_sleep_current = state;

	else

		error = -EINVAL;



 out:

	pm_autosleep_unlock();

	return error ? error : n;

}



power_attr(mem_sleep);

#endif /* CONFIG_SUSPEND */



#ifdef CONFIG_PM_DEBUG

int pm_test_level = TEST_NONE;
@@ -368,12 +440,16 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr, 
	}



	state = decode_state(buf, n);

	if (state < PM_SUSPEND_MAX)

	if (state < PM_SUSPEND_MAX) {

		if (state == PM_SUSPEND_MEM)

			state = mem_sleep_current;



		error = pm_suspend(state);

	else if (state == PM_SUSPEND_MAX)

	} else if (state == PM_SUSPEND_MAX) {

		error = hibernate();

	else

	} else {

		error = -EINVAL;

	}



 out:

	pm_autosleep_unlock();
@@ -485,6 +561,9 @@ static ssize_t autosleep_store(struct kobject *kobj, 
	    && strcmp(buf, "off") && strcmp(buf, "off\n"))

		return -EINVAL;



	if (state == PM_SUSPEND_MEM)

		state = mem_sleep_current;



	error = pm_autosleep_set_state(state);

	return error ? error : n;

}
@@ -602,6 +681,9 @@ static struct attribute * g[] = { 
#ifdef CONFIG_PM_SLEEP

	&pm_async_attr.attr,

	&wakeup_count_attr.attr,

#ifdef CONFIG_SUSPEND

	&mem_sleep_attr.attr,

#endif

#ifdef CONFIG_PM_AUTOSLEEP

	&autosleep_attr.attr,

#endif

kernel/power/power.h

+5 −1
Original line number Diff line number Diff line
@@ -189,11 +189,15 @@ extern void swsusp_show_speed(ktime_t, ktime_t, unsigned int, char *); 


#ifdef CONFIG_SUSPEND

/* kernel/power/suspend.c */

extern const char *pm_labels[];

extern const char * const pm_labels[];

extern const char *pm_states[];

extern const char *mem_sleep_states[];

extern suspend_state_t mem_sleep_current;



extern int suspend_devices_and_enter(suspend_state_t state);

#else /* !CONFIG_SUSPEND */

#define mem_sleep_current	PM_SUSPEND_ON



static inline int suspend_devices_and_enter(suspend_state_t state)

{

	return -ENOSYS;

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