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+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Timer subsystem related configuration options
+#
+
+# Options selectable by arch Kconfig
+
+# Watchdog function for clocksources to detect instabilities
+config CLOCKSOURCE_WATCHDOG
+ bool
+
+# Architecture has extra clocksource data
+config ARCH_CLOCKSOURCE_DATA
+ bool
+
+# Architecture has extra clocksource init called from registration
+config ARCH_CLOCKSOURCE_INIT
+ bool
+
+# Clocksources require validation of the clocksource against the last
+# cycle update - x86/TSC misfeature
+config CLOCKSOURCE_VALIDATE_LAST_CYCLE
+ bool
+
+# Timekeeping vsyscall support
+config GENERIC_TIME_VSYSCALL
+ bool
+
+# Old style timekeeping
+config ARCH_USES_GETTIMEOFFSET
+ bool
+
+# The generic clock events infrastructure
+config GENERIC_CLOCKEVENTS
+ bool
+
+# Architecture can handle broadcast in a driver-agnostic way
+config ARCH_HAS_TICK_BROADCAST
+ bool
+
+# Clockevents broadcasting infrastructure
+config GENERIC_CLOCKEVENTS_BROADCAST
+ bool
+ depends on GENERIC_CLOCKEVENTS
+
+# Automatically adjust the min. reprogramming time for
+# clock event device
+config GENERIC_CLOCKEVENTS_MIN_ADJUST
+ bool
+
+# Generic update of CMOS clock
+config GENERIC_CMOS_UPDATE
+ bool
+
+# Select to handle posix CPU timers from task_work
+# and not from the timer interrupt context
+config 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
+
+if GENERIC_CLOCKEVENTS
+menu "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
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ 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)"
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ 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
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ # We need at least one periodic CPU for timekeeping
+ depends on SMP
+ depends on HAVE_CONTEXT_TRACKING
+ # 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.
+
+ This is implemented at the expense of some overhead in user <-> kernel
+ transitions: syscalls, exceptions and interrupts. Even when it's
+ dynamically off.
+
+ Say N.
+
+endchoice
+
+config CONTEXT_TRACKING
+ bool
+
+config CONTEXT_TRACKING_FORCE
+ bool "Force context tracking"
+ depends on CONTEXT_TRACKING
+ default y if !NO_HZ_FULL
+ help
+ The major pre-requirement for full dynticks to work is to
+ support the 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
+ context tracking backend but doesn't yet fullfill all the
+ requirements to make the full dynticks feature working.
+ Without the full dynticks, there is no way to test the support
+ for 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 context tracking on all
+ CPUs in the system.
+
+ Say Y only if you're working on the development of an
+ architecture backend for the 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"
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ 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"
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ 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.
+
+endmenu
+endif