[linux-2.6-block.git] / kernel / power / Kconfig

# SPDX-License-Identifier: GPL-2.0-only
config SUSPEND
	bool "Suspend to RAM and standby"
	depends on ARCH_SUSPEND_POSSIBLE
	default y
	---help---
	  Allow the system to enter sleep states in which main memory is
	  powered and thus its contents are preserved, such as the
	  suspend-to-RAM state (e.g. the ACPI S3 state).

config SUSPEND_FREEZER
	bool "Enable freezer for suspend to RAM/standby" \
		if ARCH_WANTS_FREEZER_CONTROL || BROKEN
	depends on SUSPEND
	default y
	help
	  This allows you to turn off the freezer for suspend. If this is
	  done, no tasks are frozen for suspend to RAM/standby.

	  Turning OFF this setting is NOT recommended! If in doubt, say Y.

config SUSPEND_SKIP_SYNC
	bool "Skip kernel's sys_sync() on suspend to RAM/standby"
	depends on SUSPEND
	depends on EXPERT
	help
	  Skip the kernel sys_sync() before freezing user processes.
	  Some systems prefer not to pay this cost on every invocation
	  of suspend, or they are content with invoking sync() from
	  user-space before invoking suspend.  Say Y if that's your case.

config HIBERNATE_CALLBACKS
	bool

config HIBERNATION
	bool "Hibernation (aka 'suspend to disk')"
	depends on SWAP && ARCH_HIBERNATION_POSSIBLE
	select HIBERNATE_CALLBACKS
	select LZO_COMPRESS
	select LZO_DECOMPRESS
	select CRC32
	---help---
	  Enable the suspend to disk (STD) functionality, which is usually
	  called "hibernation" in user interfaces.  STD checkpoints the
	  system and powers it off; and restores that checkpoint on reboot.

	  You can suspend your machine with 'echo disk > /sys/power/state'
	  after placing resume=/dev/swappartition on the kernel command line
	  in your bootloader's configuration file.

	  Alternatively, you can use the additional userland tools available
	  from <http://suspend.sf.net>.

	  In principle it does not require ACPI or APM, although for example
	  ACPI will be used for the final steps when it is available.  One
	  of the reasons to use software suspend is that the firmware hooks
	  for suspend states like suspend-to-RAM (STR) often don't work very
	  well with Linux.

	  It creates an image which is saved in your active swap. Upon the next
	  boot, pass the 'resume=/dev/swappartition' argument to the kernel to
	  have it detect the saved image, restore memory state from it, and
	  continue to run as before. If you do not want the previous state to
	  be reloaded, then use the 'noresume' kernel command line argument.
	  Note, however, that fsck will be run on your filesystems and you will
	  need to run mkswap against the swap partition used for the suspend.

	  It also works with swap files to a limited extent (for details see
	  <file:Documentation/power/swsusp-and-swap-files.rst>).

	  Right now you may boot without resuming and resume later but in the
	  meantime you cannot use the swap partition(s)/file(s) involved in
	  suspending.  Also in this case you must not use the filesystems
	  that were mounted before the suspend.  In particular, you MUST NOT
	  MOUNT any journaled filesystems mounted before the suspend or they
	  will get corrupted in a nasty way.

	  For more information take a look at <file:Documentation/power/swsusp.rst>.

config ARCH_SAVE_PAGE_KEYS
	bool

config PM_STD_PARTITION
	string "Default resume partition"
	depends on HIBERNATION
	default ""
	---help---
	  The default resume partition is the partition that the suspend-
	  to-disk implementation will look for a suspended disk image. 

	  The partition specified here will be different for almost every user. 
	  It should be a valid swap partition (at least for now) that is turned
	  on before suspending. 

	  The partition specified can be overridden by specifying:

		resume=/dev/<other device> 

	  which will set the resume partition to the device specified. 

	  Note there is currently not a way to specify which device to save the
	  suspended image to. It will simply pick the first available swap 
	  device.

config PM_SLEEP
	def_bool y
	depends on SUSPEND || HIBERNATE_CALLBACKS
	select PM
	select SRCU

config PM_SLEEP_SMP
	def_bool y
	depends on SMP
	depends on ARCH_SUSPEND_POSSIBLE || ARCH_HIBERNATION_POSSIBLE
	depends on PM_SLEEP
	select HOTPLUG_CPU

config PM_SLEEP_SMP_NONZERO_CPU
	def_bool y
	depends on PM_SLEEP_SMP
	depends on ARCH_SUSPEND_NONZERO_CPU
	---help---
	If an arch can suspend (for suspend, hibernate, kexec, etc) on a
	non-zero numbered CPU, it may define ARCH_SUSPEND_NONZERO_CPU. This
	will allow nohz_full mask to include CPU0.

config PM_AUTOSLEEP
	bool "Opportunistic sleep"
	depends on PM_SLEEP
	default n
	---help---
	Allow the kernel to trigger a system transition into a global sleep
	state automatically whenever there are no active wakeup sources.

config PM_WAKELOCKS
	bool "User space wakeup sources interface"
	depends on PM_SLEEP
	default n
	---help---
	Allow user space to create, activate and deactivate wakeup source
	objects with the help of a sysfs-based interface.

config PM_WAKELOCKS_LIMIT
	int "Maximum number of user space wakeup sources (0 = no limit)"
	range 0 100000
	default 100
	depends on PM_WAKELOCKS

config PM_WAKELOCKS_GC
	bool "Garbage collector for user space wakeup sources"
	depends on PM_WAKELOCKS
	default y

config PM
	bool "Device power management core functionality"
	---help---
	  Enable functionality allowing I/O devices to be put into energy-saving
	  (low power) states, for example after a specified period of inactivity
	  (autosuspended), and woken up in response to a hardware-generated
	  wake-up event or a driver's request.

	  Hardware support is generally required for this functionality to work
	  and the bus type drivers of the buses the devices are on are
	  responsible for the actual handling of device suspend requests and
	  wake-up events.

config PM_DEBUG
	bool "Power Management Debug Support"
	depends on PM
	---help---
	This option enables various debugging support in the Power Management
	code. This is helpful when debugging and reporting PM bugs, like
	suspend support.

config PM_ADVANCED_DEBUG
	bool "Extra PM attributes in sysfs for low-level debugging/testing"
	depends on PM_DEBUG
	---help---
	Add extra sysfs attributes allowing one to access some Power Management
	fields of device objects from user space.  If you are not a kernel
	developer interested in debugging/testing Power Management, say "no".

config PM_TEST_SUSPEND
	bool "Test suspend/resume and wakealarm during bootup"
	depends on SUSPEND && PM_DEBUG && RTC_CLASS=y
	---help---
	This option will let you suspend your machine during bootup, and
	make it wake up a few seconds later using an RTC wakeup alarm.
	Enable this with a kernel parameter like "test_suspend=mem".

	You probably want to have your system's RTC driver statically
	linked, ensuring that it's available when this test runs.

config PM_SLEEP_DEBUG
	def_bool y
	depends on PM_DEBUG && PM_SLEEP

config DPM_WATCHDOG
	bool "Device suspend/resume watchdog"
	depends on PM_DEBUG && PSTORE && EXPERT
	---help---
	  Sets up a watchdog timer to capture drivers that are
	  locked up attempting to suspend/resume a device.
	  A detected lockup causes system panic with message
	  captured in pstore device for inspection in subsequent
	  boot session.

config DPM_WATCHDOG_TIMEOUT
	int "Watchdog timeout in seconds"
	range 1 120
	default 120
	depends on DPM_WATCHDOG

config PM_TRACE
	bool
	help
	  This enables code to save the last PM event point across
	  reboot. The architecture needs to support this, x86 for
	  example does by saving things in the RTC, see below.

	  The architecture specific code must provide the extern
	  functions from <linux/resume-trace.h> as well as the
	  <asm/resume-trace.h> header with a TRACE_RESUME() macro.

	  The way the information is presented is architecture-
	  dependent, x86 will print the information during a
	  late_initcall.

config PM_TRACE_RTC
	bool "Suspend/resume event tracing"
	depends on PM_SLEEP_DEBUG
	depends on X86
	select PM_TRACE
	---help---
	This enables some cheesy code to save the last PM event point in the
	RTC across reboots, so that you can debug a machine that just hangs
	during suspend (or more commonly, during resume).

	To use this debugging feature you should attempt to suspend the
	machine, reboot it and then run

		dmesg -s 1000000 | grep 'hash matches'

	CAUTION: this option will cause your machine's real-time clock to be
	set to an invalid time after a resume.

config APM_EMULATION
	tristate "Advanced Power Management Emulation"
	depends on SYS_SUPPORTS_APM_EMULATION
	help
	  APM is a BIOS specification for saving power using several different
	  techniques. This is mostly useful for battery powered laptops with
	  APM compliant BIOSes. If you say Y here, the system time will be
	  reset after a RESUME operation, the /proc/apm device will provide
	  battery status information, and user-space programs will receive
	  notification of APM "events" (e.g. battery status change).

	  In order to use APM, you will need supporting software. For location
	  and more information, read <file:Documentation/power/apm-acpi.rst>
	  and the Battery Powered Linux mini-HOWTO, available from
	  <http://www.tldp.org/docs.html#howto>.

	  This driver does not spin down disk drives (see the hdparm(8)
	  manpage ("man 8 hdparm") for that), and it doesn't turn off
	  VESA-compliant "green" monitors.

	  Generally, if you don't have a battery in your machine, there isn't
	  much point in using this driver and you should say N. If you get
	  random kernel OOPSes or reboots that don't seem to be related to
	  anything, try disabling/enabling this option (or disabling/enabling
	  APM in your BIOS).

config PM_CLK
	def_bool y
	depends on PM && HAVE_CLK

config PM_GENERIC_DOMAINS
	bool
	depends on PM

config WQ_POWER_EFFICIENT_DEFAULT
	bool "Enable workqueue power-efficient mode by default"
	depends on PM
	default n
	help
	  Per-cpu workqueues are generally preferred because they show
	  better performance thanks to cache locality; unfortunately,
	  per-cpu workqueues tend to be more power hungry than unbound
	  workqueues.

	  Enabling workqueue.power_efficient kernel parameter makes the
	  per-cpu workqueues which were observed to contribute
	  significantly to power consumption unbound, leading to measurably
	  lower power usage at the cost of small performance overhead.

	  This config option determines whether workqueue.power_efficient
	  is enabled by default.

	  If in doubt, say N.

config PM_GENERIC_DOMAINS_SLEEP
	def_bool y
	depends on PM_SLEEP && PM_GENERIC_DOMAINS

config PM_GENERIC_DOMAINS_OF
	def_bool y
	depends on PM_GENERIC_DOMAINS && OF

config CPU_PM
	bool

config ENERGY_MODEL
	bool "Energy Model for CPUs"
	depends on SMP
	depends on CPU_FREQ
	default n
	help
	  Several subsystems (thermal and/or the task scheduler for example)
	  can leverage information about the energy consumed by CPUs to make
	  smarter decisions. This config option enables the framework from
	  which subsystems can access the energy models.

	  The exact usage of the energy model is subsystem-dependent.

	  If in doubt, say N.
Commit	Line	Data
ec8f24b7	1	# SPDX-License-Identifier: GPL-2.0-only
296699de RW	2	config SUSPEND
296699de RW	3	bool "Suspend to RAM and standby"
1eb208ae	4	depends on ARCH_SUSPEND_POSSIBLE
296699de RW	5	default y
	6	---help---
	7	Allow the system to enter sleep states in which main memory is
	8	powered and thus its contents are preserved, such as the
f4cb5700	9	suspend-to-RAM state (e.g. the ACPI S3 state).
296699de	10
b28f5081 JB	11	config SUSPEND_FREEZER
	12	bool "Enable freezer for suspend to RAM/standby" \
	13	if ARCH_WANTS_FREEZER_CONTROL \|\| BROKEN
	14	depends on SUSPEND
	15	default y
	16	help
	17	This allows you to turn off the freezer for suspend. If this is
	18	done, no tasks are frozen for suspend to RAM/standby.
	19
	20	Turning OFF this setting is NOT recommended! If in doubt, say Y.
	21
2fd77fff LB	22	config SUSPEND_SKIP_SYNC
	23	bool "Skip kernel's sys_sync() on suspend to RAM/standby"
	24	depends on SUSPEND
	25	depends on EXPERT
	26	help
	27	Skip the kernel sys_sync() before freezing user processes.
	28	Some systems prefer not to pay this cost on every invocation
	29	of suspend, or they are content with invoking sync() from
	30	user-space before invoking suspend. Say Y if that's your case.
	31
1f112cee RW	32	config HIBERNATE_CALLBACKS
	33	bool
	34
b0cb1a19	35	config HIBERNATION
296699de	36	bool "Hibernation (aka 'suspend to disk')"
1eb208ae	37	depends on SWAP && ARCH_HIBERNATION_POSSIBLE
1f112cee	38	select HIBERNATE_CALLBACKS
f996fc96 BS	39	select LZO_COMPRESS
f996fc96 BS	40	select LZO_DECOMPRESS
081a9d04	41	select CRC32
1da177e4	42	---help---
a7ee2e5f DB	43	Enable the suspend to disk (STD) functionality, which is usually
	44	called "hibernation" in user interfaces. STD checkpoints the
	45	system and powers it off; and restores that checkpoint on reboot.
1da177e4	46
23b168d4 PM	47	You can suspend your machine with 'echo disk > /sys/power/state'
	48	after placing resume=/dev/swappartition on the kernel command line
	49	in your bootloader's configuration file.
	50
c7276fde RW	51	Alternatively, you can use the additional userland tools available
	52	from <http://suspend.sf.net>.
	53
	54	In principle it does not require ACPI or APM, although for example
a7ee2e5f DB	55	ACPI will be used for the final steps when it is available. One
	56	of the reasons to use software suspend is that the firmware hooks
	57	for suspend states like suspend-to-RAM (STR) often don't work very
	58	well with Linux.
c7276fde RW	59
c7276fde RW	60	It creates an image which is saved in your active swap. Upon the next
1da177e4 LT	61	boot, pass the 'resume=/dev/swappartition' argument to the kernel to
	62	have it detect the saved image, restore memory state from it, and
	63	continue to run as before. If you do not want the previous state to
c7276fde RW	64	be reloaded, then use the 'noresume' kernel command line argument.
	65	Note, however, that fsck will be run on your filesystems and you will
	66	need to run mkswap against the swap partition used for the suspend.
1da177e4	67
c7276fde	68	It also works with swap files to a limited extent (for details see
151f4e2b	69	<file:Documentation/power/swsusp-and-swap-files.rst>).
1da177e4	70
c7276fde RW	71	Right now you may boot without resuming and resume later but in the
	72	meantime you cannot use the swap partition(s)/file(s) involved in
	73	suspending. Also in this case you must not use the filesystems
	74	that were mounted before the suspend. In particular, you MUST NOT
	75	MOUNT any journaled filesystems mounted before the suspend or they
	76	will get corrupted in a nasty way.
1da177e4	77
151f4e2b	78	For more information take a look at <file:Documentation/power/swsusp.rst>.
471b40d0	79
85055dd8 MS	80	config ARCH_SAVE_PAGE_KEYS
	81	bool
	82
1da177e4 LT	83	config PM_STD_PARTITION
1da177e4 LT	84	string "Default resume partition"
b0cb1a19	85	depends on HIBERNATION
1da177e4 LT	86	default ""
	87	---help---
	88	The default resume partition is the partition that the suspend-
	89	to-disk implementation will look for a suspended disk image.
	90
	91	The partition specified here will be different for almost every user.
	92	It should be a valid swap partition (at least for now) that is turned
	93	on before suspending.
	94
	95	The partition specified can be overridden by specifying:
	96
	97	resume=/dev/<other device>
	98
	99	which will set the resume partition to the device specified.
	100
	101	Note there is currently not a way to specify which device to save the
	102	suspended image to. It will simply pick the first available swap
	103	device.
	104
196ec243	105	config PM_SLEEP
cf4fb80c	106	def_bool y
d419e4c0	107	depends on SUSPEND \|\| HIBERNATE_CALLBACKS
464ed18e	108	select PM
3df6f61f	109	select SRCU
196ec243 RW	110
196ec243 RW	111	config PM_SLEEP_SMP
cf4fb80c	112	def_bool y
196ec243 RW	113	depends on SMP
	114	depends on ARCH_SUSPEND_POSSIBLE \|\| ARCH_HIBERNATION_POSSIBLE
	115	depends on PM_SLEEP
196ec243	116	select HOTPLUG_CPU
196ec243	117
9ca12ac0 NP	118	config PM_SLEEP_SMP_NONZERO_CPU
	119	def_bool y
	120	depends on PM_SLEEP_SMP
	121	depends on ARCH_SUSPEND_NONZERO_CPU
	122	---help---
	123	If an arch can suspend (for suspend, hibernate, kexec, etc) on a
	124	non-zero numbered CPU, it may define ARCH_SUSPEND_NONZERO_CPU. This
	125	will allow nohz_full mask to include CPU0.
	126
7483b4a4 RW	127	config PM_AUTOSLEEP
	128	bool "Opportunistic sleep"
	129	depends on PM_SLEEP
	130	default n
	131	---help---
	132	Allow the kernel to trigger a system transition into a global sleep
	133	state automatically whenever there are no active wakeup sources.
	134
b86ff982 RW	135	config PM_WAKELOCKS
	136	bool "User space wakeup sources interface"
	137	depends on PM_SLEEP
	138	default n
	139	---help---
	140	Allow user space to create, activate and deactivate wakeup source
	141	objects with the help of a sysfs-based interface.
	142
c73893e2 RW	143	config PM_WAKELOCKS_LIMIT
	144	int "Maximum number of user space wakeup sources (0 = no limit)"
	145	range 0 100000
	146	default 100
	147	depends on PM_WAKELOCKS
	148
4e585d25 RW	149	config PM_WAKELOCKS_GC
	150	bool "Garbage collector for user space wakeup sources"
	151	depends on PM_WAKELOCKS
	152	default y
	153
464ed18e RW	154	config PM
464ed18e RW	155	bool "Device power management core functionality"
196ec243 RW	156	---help---
196ec243 RW	157	Enable functionality allowing I/O devices to be put into energy-saving
464ed18e RW	158	(low power) states, for example after a specified period of inactivity
464ed18e RW	159	(autosuspended), and woken up in response to a hardware-generated
196ec243 RW	160	wake-up event or a driver's request.
	161
	162	Hardware support is generally required for this functionality to work
	163	and the bus type drivers of the buses the devices are on are
464ed18e	164	responsible for the actual handling of device suspend requests and
196ec243 RW	165	wake-up events.
196ec243 RW	166
196ec243 RW	167	config PM_DEBUG
	168	bool "Power Management Debug Support"
	169	depends on PM
	170	---help---
	171	This option enables various debugging support in the Power Management
	172	code. This is helpful when debugging and reporting PM bugs, like
	173	suspend support.
	174
196ec243 RW	175	config PM_ADVANCED_DEBUG
	176	bool "Extra PM attributes in sysfs for low-level debugging/testing"
	177	depends on PM_DEBUG
196ec243 RW	178	---help---
	179	Add extra sysfs attributes allowing one to access some Power Management
	180	fields of device objects from user space. If you are not a kernel
	181	developer interested in debugging/testing Power Management, say "no".
	182
196ec243 RW	183	config PM_TEST_SUSPEND
	184	bool "Test suspend/resume and wakealarm during bootup"
	185	depends on SUSPEND && PM_DEBUG && RTC_CLASS=y
	186	---help---
	187	This option will let you suspend your machine during bootup, and
	188	make it wake up a few seconds later using an RTC wakeup alarm.
	189	Enable this with a kernel parameter like "test_suspend=mem".
	190
	191	You probably want to have your system's RTC driver statically
	192	linked, ensuring that it's available when this test runs.
	193
b2df1d4f	194	config PM_SLEEP_DEBUG
196ec243	195	def_bool y
88a6f33e	196	depends on PM_DEBUG && PM_SLEEP
196ec243	197
70fea60d BG	198	config DPM_WATCHDOG
70fea60d BG	199	bool "Device suspend/resume watchdog"
5b3f249c	200	depends on PM_DEBUG && PSTORE && EXPERT
70fea60d BG	201	---help---
	202	Sets up a watchdog timer to capture drivers that are
	203	locked up attempting to suspend/resume a device.
	204	A detected lockup causes system panic with message
	205	captured in pstore device for inspection in subsequent
	206	boot session.
	207
	208	config DPM_WATCHDOG_TIMEOUT
	209	int "Watchdog timeout in seconds"
	210	range 1 120
5b3f249c	211	default 120
70fea60d BG	212	depends on DPM_WATCHDOG
70fea60d BG	213
196ec243 RW	214	config PM_TRACE
	215	bool
	216	help
	217	This enables code to save the last PM event point across
	218	reboot. The architecture needs to support this, x86 for
	219	example does by saving things in the RTC, see below.
	220
	221	The architecture specific code must provide the extern
	222	functions from <linux/resume-trace.h> as well as the
	223	<asm/resume-trace.h> header with a TRACE_RESUME() macro.
	224
	225	The way the information is presented is architecture-
	226	dependent, x86 will print the information during a
	227	late_initcall.
	228
	229	config PM_TRACE_RTC
	230	bool "Suspend/resume event tracing"
b2df1d4f	231	depends on PM_SLEEP_DEBUG
196ec243 RW	232	depends on X86
196ec243 RW	233	select PM_TRACE
196ec243 RW	234	---help---
	235	This enables some cheesy code to save the last PM event point in the
	236	RTC across reboots, so that you can debug a machine that just hangs
	237	during suspend (or more commonly, during resume).
	238
	239	To use this debugging feature you should attempt to suspend the
	240	machine, reboot it and then run
	241
	242	dmesg -s 1000000 \| grep 'hash matches'
	243
	244	CAUTION: this option will cause your machine's real-time clock to be
	245	set to an invalid time after a resume.
	246
7726942f RB	247	config APM_EMULATION
7726942f RB	248	tristate "Advanced Power Management Emulation"
993e9fe1	249	depends on SYS_SUPPORTS_APM_EMULATION
7726942f RB	250	help
	251	APM is a BIOS specification for saving power using several different
	252	techniques. This is mostly useful for battery powered laptops with
	253	APM compliant BIOSes. If you say Y here, the system time will be
	254	reset after a RESUME operation, the /proc/apm device will provide
	255	battery status information, and user-space programs will receive
	256	notification of APM "events" (e.g. battery status change).
	257
	258	In order to use APM, you will need supporting software. For location
151f4e2b	259	and more information, read <file:Documentation/power/apm-acpi.rst>
2dc98fd3	260	and the Battery Powered Linux mini-HOWTO, available from
7726942f RB	261	<http://www.tldp.org/docs.html#howto>.
	262
	263	This driver does not spin down disk drives (see the hdparm(8)
	264	manpage ("man 8 hdparm") for that), and it doesn't turn off
	265	VESA-compliant "green" monitors.
	266
	267	Generally, if you don't have a battery in your machine, there isn't
	268	much point in using this driver and you should say N. If you get
	269	random kernel OOPSes or reboots that don't seem to be related to
	270	anything, try disabling/enabling this option (or disabling/enabling
	271	APM in your BIOS).
5e928f77	272
b7b95920	273	config PM_CLK
85eb8c8d	274	def_bool y
b7b95920	275	depends on PM && HAVE_CLK
f721889f RW	276
	277	config PM_GENERIC_DOMAINS
	278	bool
	279	depends on PM
17f2ae7f	280
cee22a15 VK	281	config WQ_POWER_EFFICIENT_DEFAULT
	282	bool "Enable workqueue power-efficient mode by default"
	283	depends on PM
	284	default n
	285	help
	286	Per-cpu workqueues are generally preferred because they show
	287	better performance thanks to cache locality; unfortunately,
	288	per-cpu workqueues tend to be more power hungry than unbound
	289	workqueues.
	290
	291	Enabling workqueue.power_efficient kernel parameter makes the
	292	per-cpu workqueues which were observed to contribute
	293	significantly to power consumption unbound, leading to measurably
	294	lower power usage at the cost of small performance overhead.
	295
	296	This config option determines whether workqueue.power_efficient
	297	is enabled by default.
	298
	299	If in doubt, say N.
	300
77f827de RW	301	config PM_GENERIC_DOMAINS_SLEEP
	302	def_bool y
	303	depends on PM_SLEEP && PM_GENERIC_DOMAINS
	304
aa42240a TF	305	config PM_GENERIC_DOMAINS_OF
aa42240a TF	306	def_bool y
a4a8c2c4	307	depends on PM_GENERIC_DOMAINS && OF
aa42240a	308
ab10023e CC	309	config CPU_PM
ab10023e CC	310	bool
27871f7a QP	311
	312	config ENERGY_MODEL
	313	bool "Energy Model for CPUs"
	314	depends on SMP
	315	depends on CPU_FREQ
	316	default n
	317	help
	318	Several subsystems (thermal and/or the task scheduler for example)
	319	can leverage information about the energy consumed by CPUs to make
	320	smarter decisions. This config option enables the framework from
	321	which subsystems can access the energy models.
	322
	323	The exact usage of the energy model is subsystem-dependent.
	324
	325	If in doubt, say N.