linux-imx/kernel/time/Kconfig

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

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