# SPDX-License-Identifier: GPL-2.0-only## Timer subsystem related configuration options# # Options selectable by arch Kconfig # Watchdog function for clocksources to detect instabilitiesconfig CLOCKSOURCE_WATCHDOG	bool # Architecture has extra clocksource dataconfig ARCH_CLOCKSOURCE_DATA	bool # Architecture has extra clocksource init called from registrationconfig ARCH_CLOCKSOURCE_INIT	bool # Clocksources require validation of the clocksource against the last# cycle update - x86/TSC misfeatureconfig CLOCKSOURCE_VALIDATE_LAST_CYCLE	bool # Timekeeping vsyscall supportconfig GENERIC_TIME_VSYSCALL	bool # The generic clock events infrastructureconfig GENERIC_CLOCKEVENTS	def_bool !LEGACY_TIMER_TICK # Architecture can handle broadcast in a driver-agnostic wayconfig ARCH_HAS_TICK_BROADCAST	bool # Clockevents broadcasting infrastructureconfig GENERIC_CLOCKEVENTS_BROADCAST	bool	depends on GENERIC_CLOCKEVENTS # Automatically adjust the min. reprogramming time for# clock event deviceconfig GENERIC_CLOCKEVENTS_MIN_ADJUST	bool # Generic update of CMOS clockconfig GENERIC_CMOS_UPDATE	bool # Select to handle posix CPU timers from task_work# and not from the timer interrupt contextconfig HAVE_POSIX_CPU_TIMERS_TASK_WORK	bool config POSIX_CPU_TIMERS_TASK_WORK	bool	default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK config LEGACY_TIMER_TICK	bool	help	  The legacy timer tick helper is used by platforms that	  lack support for the generic clockevent framework.	  New platforms should use generic clockevents instead. config TIME_KUNIT_TEST	tristate "KUnit test for kernel/time functions" if !KUNIT_ALL_TESTS	depends on KUNIT	default KUNIT_ALL_TESTS	help	  Enable this option to test RTC library functions. 	  If unsure, say N. config CONTEXT_TRACKING	bool config CONTEXT_TRACKING_IDLE	bool	select CONTEXT_TRACKING	help	  Tracks idle state on behalf of RCU. if GENERIC_CLOCKEVENTSmenu "Timers subsystem" # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is# only related to the tick functionality. Oneshot clockevent devices# are supported independent of this.config TICK_ONESHOT	bool config NO_HZ_COMMON	bool	select TICK_ONESHOT choice	prompt "Timer tick handling"	default NO_HZ_IDLE if NO_HZ config HZ_PERIODIC	bool "Periodic timer ticks (constant rate, no dynticks)"	help	  This option keeps the tick running periodically at a constant	  rate, even when the CPU doesn't need it. config NO_HZ_IDLE	bool "Idle dynticks system (tickless idle)"	select NO_HZ_COMMON	help	  This option enables a tickless idle system: timer interrupts	  will only trigger on an as-needed basis when the system is idle.	  This is usually interesting for energy saving. 	  Most of the time you want to say Y here. config NO_HZ_FULL	bool "Full dynticks system (tickless)"	# NO_HZ_COMMON dependency	# We need at least one periodic CPU for timekeeping	depends on SMP	depends on HAVE_CONTEXT_TRACKING_USER	# VIRT_CPU_ACCOUNTING_GEN dependency	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN	select NO_HZ_COMMON	select RCU_NOCB_CPU	select VIRT_CPU_ACCOUNTING_GEN	select IRQ_WORK	select CPU_ISOLATION	help	 Adaptively try to shutdown the tick whenever possible, even when	 the CPU is running tasks. Typically this requires running a single	 task on the CPU. Chances for running tickless are maximized when	 the task mostly runs in userspace and has few kernel activity. 	 You need to fill up the nohz_full boot parameter with the	 desired range of dynticks CPUs to use it. This is implemented at	 the expense of some overhead in user <-> kernel transitions:	 syscalls, exceptions and interrupts. 	 By default, without passing the nohz_full parameter, this behaves just	 like NO_HZ_IDLE. 	 If you're a distro say Y. endchoice config CONTEXT_TRACKING_USER	bool	depends on HAVE_CONTEXT_TRACKING_USER	select CONTEXT_TRACKING	help	  Track transitions between kernel and user on behalf of RCU and	  tickless cputime accounting. The former case relies on context	  tracking to enter/exit RCU extended quiescent states. config CONTEXT_TRACKING_USER_FORCE	bool "Force user context tracking"	depends on CONTEXT_TRACKING_USER	default y if !NO_HZ_FULL	help	  The major pre-requirement for full dynticks to work is to	  support the user context tracking subsystem. But there are also	  other dependencies to provide in order to make the full	  dynticks working. 	  This option stands for testing when an arch implements the	  user context tracking backend but doesn't yet fulfill all the	  requirements to make the full dynticks feature working.	  Without the full dynticks, there is no way to test the support	  for user context tracking and the subsystems that rely on it: RCU	  userspace extended quiescent state and tickless cputime	  accounting. This option copes with the absence of the full	  dynticks subsystem by forcing the user context tracking on all	  CPUs in the system. 	  Say Y only if you're working on the development of an	  architecture backend for the user context tracking. 	  Say N otherwise, this option brings an overhead that you	  don't want in production. config NO_HZ	bool "Old Idle dynticks config"	help	  This is the old config entry that enables dynticks idle.	  We keep it around for a little while to enforce backward	  compatibility with older config files. config HIGH_RES_TIMERS	bool "High Resolution Timer Support"	select TICK_ONESHOT	help	  This option enables high resolution timer support. If your	  hardware is not capable then this option only increases	  the size of the kernel image. config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US	int "Clocksource watchdog maximum allowable skew (in μs)"	depends on CLOCKSOURCE_WATCHDOG	range 50 1000	default 125	help	  Specify the maximum amount of allowable watchdog skew in	  microseconds before reporting the clocksource to be unstable.	  The default is based on a half-second clocksource watchdog	  interval and NTP's maximum frequency drift of 500 parts	  per million.	If the clocksource is good enough for NTP,	  it is good enough for the clocksource watchdog! endmenuendif