linux-yocto/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. There's a run-time switch at '/sys/power/sync_on_suspend' to configure this behaviour. This setting changes the default for the run-tim switch. Say Y to change the default to disable the kernel sys_sync().

config HIBERNATE_CALLBACKS bool

config HIBERNATION bool "Hibernation (aka 'suspend to disk')" depends on SWAP && ARCH_HIBERNATION_POSSIBLE select HIBERNATE_CALLBACKS select CRC32 select CRYPTO select CRYPTO_LZO 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 HIBERNATION_SNAPSHOT_DEV bool "Userspace snapshot device" depends on HIBERNATION default y help Device used by the uswsusp tools.

  Say N if no snapshotting from userspace is needed, this also
  reduces the attack surface of the kernel.

  If in doubt, say Y.

choice prompt "Default compressor" default HIBERNATION_COMP_LZO depends on HIBERNATION

config HIBERNATION_COMP_LZO bool "lzo" depends on CRYPTO_LZO

config HIBERNATION_COMP_LZ4 bool "lz4" depends on CRYPTO_LZ4

endchoice

config HIBERNATION_DEF_COMP string default "lzo" if HIBERNATION_COMP_LZO default "lz4" if HIBERNATION_COMP_LZ4 help Default compressor to be used for hibernation.

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

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 help Allow the kernel to trigger a system transition into a global sleep state automatically whenever there are no active wakeup sources.

config PM_USERSPACE_AUTOSLEEP bool "Userspace opportunistic sleep" depends on PM_SLEEP help Notify kernel of aggressive userspace autosleep power management policy.

This option changes the behavior of various sleep-sensitive code to deal
with frequent userspace-initiated transitions into a global sleep state.

Saying Y here, disables code paths that most users really should keep
enabled. In particular, only enable this if it is very common to be
asleep/awake for very short periods of time (<= 2 seconds).

Only platforms, such as Android, that implement opportunistic sleep from
a userspace power manager service should enable this option; and not
other machines. Therefore, you should say N here, unless you are
extremely certain that this is what you want. The option otherwise has
bad, undesirable effects, and should not be enabled just for fun.

config PM_WAKELOCKS bool "User space wakeup sources interface" depends on PM_SLEEP 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 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 devices with DVFS (CPUs, GPUs, etc)" depends on SMP depends on CPU_FREQ help Several subsystems (thermal and/or the task scheduler for example) can leverage information about the energy consumed by devices 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.