From 24a169e3298b55834b0aa027c6c5e41a9f9124d7 Mon Sep 17 00:00:00 2001
From: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
Date: Thu, 4 Nov 2021 14:14:51 +0100
Subject: [PATCH] drivers: timer: split Kconfig

Split Kconfig into individual files for each driver. This improves
overall readability of the Kconfig options.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
---
 drivers/timer/Kconfig                   | 423 ++----------------------
 drivers/timer/Kconfig.altera_avalon     |  14 +
 drivers/timer/Kconfig.apic              |  76 +++++
 drivers/timer/Kconfig.arcv2             |  21 ++
 drivers/timer/Kconfig.arm_arch          |  26 ++
 drivers/timer/Kconfig.cavs              |  16 +
 drivers/timer/Kconfig.cc13x2_cc26x2_rtc |  14 +
 drivers/timer/Kconfig.cortex_m_systick  |  21 ++
 drivers/timer/Kconfig.esp32c3_sys       |  14 +
 drivers/timer/Kconfig.hpet              |  15 +
 drivers/timer/Kconfig.ite_it8xxx2       |  12 +
 drivers/timer/Kconfig.leon_gptimer      |  12 +
 drivers/timer/Kconfig.litex             |  12 +
 drivers/timer/Kconfig.mchp_xec_rtos     |  13 +
 drivers/timer/Kconfig.mcux_lptmr        |  12 +
 drivers/timer/Kconfig.mcux_os           |  15 +
 drivers/timer/Kconfig.native_posix      |  14 +
 drivers/timer/Kconfig.npcx_itim         |  15 +
 drivers/timer/Kconfig.nrf_rtc           |  57 ++++
 drivers/timer/Kconfig.rcar_cmt          |  13 +
 drivers/timer/Kconfig.riscv_machine     |  13 +
 drivers/timer/Kconfig.rv32m1_lptmr      |  14 +
 drivers/timer/Kconfig.sam0_rtc          |  13 +
 drivers/timer/Kconfig.xlnx_psttc        |  22 ++
 drivers/timer/Kconfig.xtensa            |  26 ++
 25 files changed, 511 insertions(+), 392 deletions(-)
 create mode 100644 drivers/timer/Kconfig.altera_avalon
 create mode 100644 drivers/timer/Kconfig.apic
 create mode 100644 drivers/timer/Kconfig.arcv2
 create mode 100644 drivers/timer/Kconfig.arm_arch
 create mode 100644 drivers/timer/Kconfig.cavs
 create mode 100644 drivers/timer/Kconfig.cc13x2_cc26x2_rtc
 create mode 100644 drivers/timer/Kconfig.cortex_m_systick
 create mode 100644 drivers/timer/Kconfig.esp32c3_sys
 create mode 100644 drivers/timer/Kconfig.hpet
 create mode 100644 drivers/timer/Kconfig.ite_it8xxx2
 create mode 100644 drivers/timer/Kconfig.leon_gptimer
 create mode 100644 drivers/timer/Kconfig.litex
 create mode 100644 drivers/timer/Kconfig.mchp_xec_rtos
 create mode 100644 drivers/timer/Kconfig.mcux_lptmr
 create mode 100644 drivers/timer/Kconfig.mcux_os
 create mode 100644 drivers/timer/Kconfig.native_posix
 create mode 100644 drivers/timer/Kconfig.npcx_itim
 create mode 100644 drivers/timer/Kconfig.nrf_rtc
 create mode 100644 drivers/timer/Kconfig.rcar_cmt
 create mode 100644 drivers/timer/Kconfig.riscv_machine
 create mode 100644 drivers/timer/Kconfig.rv32m1_lptmr
 create mode 100644 drivers/timer/Kconfig.sam0_rtc
 create mode 100644 drivers/timer/Kconfig.xlnx_psttc
 create mode 100644 drivers/timer/Kconfig.xtensa

diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index 970531cc4d..9c51c0a8af 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -7,379 +7,6 @@
 
 menu "Timer Drivers"
 
-config TIMER_HAS_64BIT_CYCLE_COUNTER
-	bool
-	help
-	  When this option is true, the k_cycle_get_64() call is
-	  available to provide values from a 64-bit cycle counter.
-
-menuconfig APIC_TIMER
-	bool "New local APIC timer"
-	depends on X86
-	depends on LOAPIC
-	select TICKLESS_CAPABLE
-	help
-	  Use the x86 local APIC in one-shot mode as the system time
-	  source.  NOTE: this probably isn't what you want except on
-	  older or idiosyncratic hardware (or environments like qemu
-	  without complete APIC emulation).  Modern hardware will work
-	  better with CONFIG_APIC_TSC_DEADLINE_TIMER.
-
-if APIC_TIMER
-
-config APIC_TIMER_IRQ
-	int "Local APIC timer IRQ"
-	default 24
-	help
-	  This option specifies the IRQ used by the local APIC timer.
-	  Note: this MUST be set to the index immediately after the
-	  last IO-APIC IRQ (the timer is the first entry in the APIC
-	  local vector table).  This footgun is not intended to be
-	  user-configurable and almost certainly should be managed via
-	  a different mechanism.
-
-config APIC_TIMER_TSC
-	bool "Use invariant TSC for sys_clock_cycle_get_32()"
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  If your CPU supports invariant TSC, and you know the ratio of the
-	  TSC frequency to CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC (the local APIC
-	  timer frequency), then enable this for a much faster and more
-	  accurate sys_clock_cycle_get_32().
-
-if APIC_TIMER_TSC
-
-config APIC_TIMER_TSC_N
-	int "TSC to local APIC timer frequency multiplier (N)"
-	default 1
-
-config APIC_TIMER_TSC_M
-	int "TSC to local APIC timer frequency divisor (M)"
-	default 1
-
-endif # APIC_TIMER_TSC
-
-endif # APIC_TIMER
-
-config APIC_TSC_DEADLINE_TIMER
-	bool "Even newer APIC timer using TSC deadline mode"
-	depends on X86
-	select LOAPIC
-	select TICKLESS_CAPABLE
-	help
-	  Extremely simple timer driver based the local APIC TSC
-	  deadline capability.  The use of a free-running 64 bit
-	  counter with comparator eliminates almost all edge cases
-	  from the handling, and the near-instruction-cycle resolution
-	  permits effectively unlimited precision where needed (the
-	  limit becomes the CPU time taken to execute the timing
-	  logic). SMP-safe and very fast, this should be the obvious
-	  choice for any x86 device with invariant TSC and TSC
-	  deadline capability.
-
-config APIC_TIMER_IRQ_PRIORITY
-	int "Local APIC timer interrupt priority"
-	depends on APIC_TIMER || APIC_TSC_DEADLINE_TIMER
-	default 4
-	help
-	  This option specifies the interrupt priority used by the
-	  local APIC timer.
-
-config HPET_TIMER
-	bool "HPET timer"
-	select IOAPIC if X86
-	select LOAPIC if X86
-	imply TIMER_READS_ITS_FREQUENCY_AT_RUNTIME
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This option selects High Precision Event Timer (HPET) as a
-	  system timer.
-
-menuconfig ARCV2_TIMER
-	bool "ARC Timer"
-	default y
-	depends on ARC
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the ARCv2 processor timer 0
-	  and provides the standard "system clock driver" interfaces.
-
-config ARCV2_TIMER_IRQ_PRIORITY
-	int "ARC timer interrupt priority"
-	default 0
-	depends on ARCV2_TIMER
-	help
-	  This option specifies the IRQ priority used by the ARC timer. Lower
-	  values have higher priority.
-
-config ARM_ARCH_TIMER
-	bool "ARM architected timer"
-	depends on GIC
-	select ARCH_HAS_CUSTOM_BUSY_WAIT
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the ARM architected
-	  timer which provides per-cpu timers attached to a GIC to deliver its
-	  per-processor interrupts via PPIs.
-
-DT_COMPAT_ARM_V6M_SYSTICK := arm,armv6m-systick
-DT_COMPAT_ARM_V7M_SYSTICK := arm,armv7m-systick
-DT_COMPAT_ARM_V8M_SYSTICK := arm,armv8m-systick
-DT_COMPAT_ARM_V8_1M_SYSTICK := arm,armv8.1m-systick
-
-config ARM_ARCH_TIMER_ERRATUM_740657
-	bool "ARM architected timer is affected by ARM erratum 740657"
-	depends on ARM_ARCH_TIMER
-	help
-	  This option indicates that the ARM architected timer as implemented
-	  in the target hardware is affected by the ARM erratum 740657 (comp.
-	  ARM Cortex-A9 processors Software Developers Errata Notice, ARM
-	  document ID032315) which leads to an additional, spurious interrupt
-	  indication upon every actual timer interrupt. This option activates
-	  the workaround for the erratum within the timer driver.
-
-config CORTEX_M_SYSTICK
-	bool "Cortex-M SYSTICK timer"
-	depends on CPU_CORTEX_M_HAS_SYSTICK
-	default $(dt_compat_enabled,$(DT_COMPAT_ARM_V6M_SYSTICK)) || \
-		$(dt_compat_enabled,$(DT_COMPAT_ARM_V7M_SYSTICK)) || \
-		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8M_SYSTICK)) || \
-		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8_1M_SYSTICK))
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the Cortex-M processor
-	  SYSTICK timer and provides the standard "system clock driver" interfaces.
-
-config ALTERA_AVALON_TIMER
-	bool "Altera Avalon Interval Timer"
-	default y
-	depends on NIOS2
-	help
-	  This module implements a kernel device driver for the Altera Avalon
-	  Interval Timer as described in the Embedded IP documentation, for use
-	  with Nios II and possibly other Altera soft CPUs. It provides the
-	  standard "system clock driver" interfaces.
-
-config ITE_IT8XXX2_TIMER
-	bool "ITE it8xxx2 timer driver"
-	depends on SOC_IT8XXX2
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the ITE it8xxx2
-	  HW timer model
-
-config NRF_RTC_TIMER
-	bool "nRF Real Time Counter (NRF_RTC1) Timer"
-	depends on CLOCK_CONTROL
-	depends on SOC_COMPATIBLE_NRF
-	select TICKLESS_CAPABLE
-	select NRF_HW_RTC1_RESERVED
-	help
-	  This module implements a kernel device driver for the nRF Real Time
-	  Counter NRF_RTC1 and provides the standard "system clock driver"
-	  interfaces.
-
-if NRF_RTC_TIMER
-
-config NRF_RTC_TIMER_USER_CHAN_COUNT
-	int "Additional channels that can be used"
-	default 0
-	help
-	  Use nrf_rtc_timer.h API. Driver is not managing allocation of channels.
-
-choice
-	prompt "Clock startup policy"
-	default SYSTEM_CLOCK_WAIT_FOR_STABILITY
-
-config SYSTEM_CLOCK_NO_WAIT
-	bool "No wait"
-	help
-	  System clock source is initiated but does not wait for clock readiness.
-	  When this option is picked, system clock may not be ready when code relying
-	  on kernel API is executed. Requested timeouts will be prolonged by the
-	  remaining startup time.
-
-config SYSTEM_CLOCK_WAIT_FOR_AVAILABILITY
-	bool "Wait for availability"
-	help
-	  System clock source initialization waits until clock is available. In some
-	  systems, clock initially runs from less accurate source which has faster
-	  startup time and then seamlessly switches to the target clock source when
-	  it is ready. When this option is picked, system clock is available after
-	  system clock driver initialization but it may be less accurate. Option is
-	  equivalent to waiting for stability if clock source does not have
-	  intermediate state.
-
-config SYSTEM_CLOCK_WAIT_FOR_STABILITY
-	bool "Wait for stability"
-	help
-	  System clock source initialization waits until clock is stable. When this
-	  option is picked, system clock is available and stable after system clock
-	  driver initialization.
-
-endchoice
-
-endif # NRF_RTC_TIMER
-
-source "drivers/timer/Kconfig.stm32_lptim"
-
-config RISCV_MACHINE_TIMER
-	bool "RISCV Machine Timer"
-	depends on SOC_FAMILY_RISCV_PRIVILEGE
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the generic RISCV machine
-	  timer driver. It provides the standard "system clock driver" interfaces.
-
-config RV32M1_LPTMR_TIMER
-	bool "RV32M1 LPTMR system timer driver"
-	default y
-	depends on SOC_OPENISA_RV32M1_RISCV32
-	depends on RV32M1_INTMUX
-	help
-	  This module implements a kernel device driver for using the LPTMR
-	  peripheral as the system clock. It provides the standard "system clock
-	  driver" interfaces.
-
-config LITEX_TIMER
-	bool "LiteX Timer"
-	default y
-	depends on SOC_RISCV32_LITEX_VEXRISCV
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for LiteX Timer.
-
-config NATIVE_POSIX_TIMER
-	bool "(POSIX) native_posix timer driver"
-	default y
-	depends on BOARD_NATIVE_POSIX
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the native_posix HW timer
-	  model
-
-config XTENSA_TIMER
-	bool "Xtensa timer support"
-	depends on XTENSA
-	default y
-	select TICKLESS_CAPABLE
-	help
-	  Enables a system timer driver for Xtensa based on the CCOUNT
-	  and CCOMPARE special registers.
-
-config ESP32C3_SYS_TIMER
-	bool "ESP32C3 sys-timer support"
-	depends on SOC_ESP32C3
-	default y
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This option enables the system timer driver for the Espressif ESP32C3
-	  and provides the standard "system clock driver" interface.
-
-config XTENSA_TIMER_ID
-	int "System timer CCOMPAREn register index"
-	default 1
-	depends on XTENSA_TIMER
-	help
-	  Index of the CCOMPARE register (and associated interrupt)
-	  used for the system timer.  Xtensa CPUs have hard-configured
-	  interrupt priorities associated with each timer, and some of
-	  them can be unmaskable (and thus not usable by OS code that
-	  need synchronization, like the timer subsystem!).  Choose
-	  carefully.  Generally you want the timer with the highest
-	  priority maskable interrupt.
-
-config SAM0_RTC_TIMER
-	bool "Atmel SAM0 series RTC timer"
-	depends on SOC_FAMILY_SAM0
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the Atmel SAM0
-	  series Real Time Counter and provides the standard "system clock
-	  driver" interfaces.
-
-config MCHP_XEC_RTOS_TIMER
-	bool "Microchip XEC series RTOS timer"
-	depends on SOC_FAMILY_MEC
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the Microchip
-	  XEC series RTOS timer and provides the standard "system clock
-	  driver" interfaces.
-
-config CC13X2_CC26X2_RTC_TIMER
-	bool "TI SimpleLink CC13x2/CC26x2 RTC timer"
-	depends on SOC_SERIES_CC13X2_CC26X2
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the TI SimpleLink
-	  CC13X2_CC26X2 series Real Time Counter and provides the standard
-	  "system clock driver" interfaces.
-
-config RCAR_CMT_TIMER
-	bool "Renesas RCar cmt timer"
-	default y
-	depends on SOC_SERIES_RCAR_GEN3
-	help
-	  This module implements a kernel device driver for the Renesas RCAR
-	  platform provides the standard "system clock driver" interfaces.
-	  If unchecked, no timer will be used.
-
-config XLNX_PSTTC_TIMER
-	bool "Xilinx PS ttc timer support"
-	default y
-	depends on SOC_XILINX_ZYNQMP
-	select TICKLESS_CAPABLE
-	help
-	  This module implements a kernel device driver for the Xilinx ZynqMP
-	  platform provides the standard "system clock driver" interfaces.
-	  If unchecked, no timer will be used.
-
-config XLNX_PSTTC_TIMER_INDEX
-	int "Xilinx PS ttc timer index"
-	range 0 3
-	default 0
-	depends on XLNX_PSTTC_TIMER
-	help
-	  This is the index of TTC timer picked to provide system clock.
-
-config CAVS_TIMER
-	bool "CAVS DSP Wall Clock Timer on Intel SoC"
-	depends on CAVS_ICTL
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  The DSP wall clock timer is a timer driven directly by
-	  external oscillator and is external to the CPU core(s).
-	  It is not as fast as the internal core clock, but provides
-	  a common and synchronized counter for all CPU cores (which
-	  is useful for SMP).
-
-config LEON_GPTIMER
-	bool "LEON timer"
-	depends on SOC_SPARC_LEON
-	select DYNAMIC_INTERRUPTS
-	help
-	  This module implements a kernel device driver for the GRLIB
-	  GPTIMER which is common in LEON systems.
-
-config NPCX_ITIM_TIMER
-	bool "Nuvoton NPCX series internal 64/32-bit timers"
-	default y
-	depends on SOC_FAMILY_NPCX
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the Nuvoton NPCX
-	  series internal 64/32-bit timers and provides the standard "system
-	  clock driver" interfaces.
-
 config SYSTEM_CLOCK_DISABLE
 	bool "API to disable system clock"
 	help
@@ -387,6 +14,12 @@ config SYSTEM_CLOCK_DISABLE
 	  needed by some subsystems (which will automatically select it), but is
 	  rarely needed by applications.
 
+config TIMER_HAS_64BIT_CYCLE_COUNTER
+	bool
+	help
+	  When this option is true, the k_cycle_get_64() call is
+	  available to provide values from a 64-bit cycle counter.
+
 config TIMER_READS_ITS_FREQUENCY_AT_RUNTIME
 	bool "Timer queries its hardware to find its frequency at runtime"
 	help
@@ -422,24 +55,30 @@ config TICKLESS_CAPABLE
 	  sys_clock_announce() (really, not to produce an interrupt at
 	  all) until the specified expiration.
 
-DT_COMPAT_NXP_OS_TIMER := nxp,os-timer
-
-config MCUX_OS_TIMER
-	bool "MCUX OS Event timer"
-	depends on HAS_MCUX_OS_TIMER
-	default $(dt_compat_enabled,$(DT_COMPAT_NXP_OS_TIMER))
-	select TICKLESS_CAPABLE
-	select TIMER_HAS_64BIT_CYCLE_COUNTER
-	help
-	  This module implements a kernel device driver for the NXP OS
-	  event timer and provides the standard "system clock driver" interfaces.
-
-config MCUX_LPTMR_TIMER
-	bool "MCUX LPTMR timer"
-	depends on HAS_MCUX_LPTMR && !COUNTER_MCUX_LPTMR
-	help
-	  This module implements a kernel device driver for the NXP MCUX Low
-	  Power Timer (LPTMR) and provides the standard "system clock driver"
-	  interfaces.
+source "drivers/timer/Kconfig.altera_avalon"
+source "drivers/timer/Kconfig.apic"
+source "drivers/timer/Kconfig.arcv2"
+source "drivers/timer/Kconfig.arm_arch"
+source "drivers/timer/Kconfig.cavs"
+source "drivers/timer/Kconfig.cc13x2_cc26x2_rtc"
+source "drivers/timer/Kconfig.cortex_m_systick"
+source "drivers/timer/Kconfig.esp32c3_sys"
+source "drivers/timer/Kconfig.hpet"
+source "drivers/timer/Kconfig.ite_it8xxx2"
+source "drivers/timer/Kconfig.leon_gptimer"
+source "drivers/timer/Kconfig.litex"
+source "drivers/timer/Kconfig.mchp_xec_rtos"
+source "drivers/timer/Kconfig.mcux_lptmr"
+source "drivers/timer/Kconfig.mcux_os"
+source "drivers/timer/Kconfig.native_posix"
+source "drivers/timer/Kconfig.npcx_itim"
+source "drivers/timer/Kconfig.nrf_rtc"
+source "drivers/timer/Kconfig.rcar_cmt"
+source "drivers/timer/Kconfig.riscv_machine"
+source "drivers/timer/Kconfig.rv32m1_lptmr"
+source "drivers/timer/Kconfig.sam0_rtc"
+source "drivers/timer/Kconfig.stm32_lptim"
+source "drivers/timer/Kconfig.xlnx_psttc"
+source "drivers/timer/Kconfig.xtensa"
 
 endmenu
diff --git a/drivers/timer/Kconfig.altera_avalon b/drivers/timer/Kconfig.altera_avalon
new file mode 100644
index 0000000000..1797c366fc
--- /dev/null
+++ b/drivers/timer/Kconfig.altera_avalon
@@ -0,0 +1,14 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config ALTERA_AVALON_TIMER
+	bool "Altera Avalon Interval Timer"
+	default y
+	depends on NIOS2
+	help
+	  This module implements a kernel device driver for the Altera Avalon
+	  Interval Timer as described in the Embedded IP documentation, for use
+	  with Nios II and possibly other Altera soft CPUs. It provides the
+	  standard "system clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.apic b/drivers/timer/Kconfig.apic
new file mode 100644
index 0000000000..23af257670
--- /dev/null
+++ b/drivers/timer/Kconfig.apic
@@ -0,0 +1,76 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+menuconfig APIC_TIMER
+	bool "New local APIC timer"
+	depends on X86
+	depends on LOAPIC
+	select TICKLESS_CAPABLE
+	help
+	  Use the x86 local APIC in one-shot mode as the system time
+	  source.  NOTE: this probably isn't what you want except on
+	  older or idiosyncratic hardware (or environments like qemu
+	  without complete APIC emulation).  Modern hardware will work
+	  better with CONFIG_APIC_TSC_DEADLINE_TIMER.
+
+if APIC_TIMER
+
+config APIC_TIMER_IRQ
+	int "Local APIC timer IRQ"
+	default 24
+	help
+	  This option specifies the IRQ used by the local APIC timer.
+	  Note: this MUST be set to the index immediately after the
+	  last IO-APIC IRQ (the timer is the first entry in the APIC
+	  local vector table).  This footgun is not intended to be
+	  user-configurable and almost certainly should be managed via
+	  a different mechanism.
+
+config APIC_TIMER_TSC
+	bool "Use invariant TSC for sys_clock_cycle_get_32()"
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  If your CPU supports invariant TSC, and you know the ratio of the
+	  TSC frequency to CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC (the local APIC
+	  timer frequency), then enable this for a much faster and more
+	  accurate sys_clock_cycle_get_32().
+
+if APIC_TIMER_TSC
+
+config APIC_TIMER_TSC_N
+	int "TSC to local APIC timer frequency multiplier (N)"
+	default 1
+
+config APIC_TIMER_TSC_M
+	int "TSC to local APIC timer frequency divisor (M)"
+	default 1
+
+endif # APIC_TIMER_TSC
+
+endif # APIC_TIMER
+
+config APIC_TSC_DEADLINE_TIMER
+	bool "Even newer APIC timer using TSC deadline mode"
+	depends on X86
+	select LOAPIC
+	select TICKLESS_CAPABLE
+	help
+	  Extremely simple timer driver based the local APIC TSC
+	  deadline capability.  The use of a free-running 64 bit
+	  counter with comparator eliminates almost all edge cases
+	  from the handling, and the near-instruction-cycle resolution
+	  permits effectively unlimited precision where needed (the
+	  limit becomes the CPU time taken to execute the timing
+	  logic). SMP-safe and very fast, this should be the obvious
+	  choice for any x86 device with invariant TSC and TSC
+	  deadline capability.
+
+config APIC_TIMER_IRQ_PRIORITY
+	int "Local APIC timer interrupt priority"
+	depends on APIC_TIMER || APIC_TSC_DEADLINE_TIMER
+	default 4
+	help
+	  This option specifies the interrupt priority used by the
+	  local APIC timer.
diff --git a/drivers/timer/Kconfig.arcv2 b/drivers/timer/Kconfig.arcv2
new file mode 100644
index 0000000000..cd262ee4c4
--- /dev/null
+++ b/drivers/timer/Kconfig.arcv2
@@ -0,0 +1,21 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+menuconfig ARCV2_TIMER
+	bool "ARC Timer"
+	default y
+	depends on ARC
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the ARCv2 processor timer 0
+	  and provides the standard "system clock driver" interfaces.
+
+config ARCV2_TIMER_IRQ_PRIORITY
+	int "ARC timer interrupt priority"
+	default 0
+	depends on ARCV2_TIMER
+	help
+	  This option specifies the IRQ priority used by the ARC timer. Lower
+	  values have higher priority.
diff --git a/drivers/timer/Kconfig.arm_arch b/drivers/timer/Kconfig.arm_arch
new file mode 100644
index 0000000000..af99bbe3dc
--- /dev/null
+++ b/drivers/timer/Kconfig.arm_arch
@@ -0,0 +1,26 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config ARM_ARCH_TIMER
+	bool "ARM architected timer"
+	depends on GIC
+	select ARCH_HAS_CUSTOM_BUSY_WAIT
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for the ARM architected
+	  timer which provides per-cpu timers attached to a GIC to deliver its
+	  per-processor interrupts via PPIs.
+
+config ARM_ARCH_TIMER_ERRATUM_740657
+	bool "ARM architected timer is affected by ARM erratum 740657"
+	depends on ARM_ARCH_TIMER
+	help
+	  This option indicates that the ARM architected timer as implemented
+	  in the target hardware is affected by the ARM erratum 740657 (comp.
+	  ARM Cortex-A9 processors Software Developers Errata Notice, ARM
+	  document ID032315) which leads to an additional, spurious interrupt
+	  indication upon every actual timer interrupt. This option activates
+	  the workaround for the erratum within the timer driver.
diff --git a/drivers/timer/Kconfig.cavs b/drivers/timer/Kconfig.cavs
new file mode 100644
index 0000000000..f5d4071082
--- /dev/null
+++ b/drivers/timer/Kconfig.cavs
@@ -0,0 +1,16 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config CAVS_TIMER
+	bool "CAVS DSP Wall Clock Timer on Intel SoC"
+	depends on CAVS_ICTL
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  The DSP wall clock timer is a timer driven directly by
+	  external oscillator and is external to the CPU core(s).
+	  It is not as fast as the internal core clock, but provides
+	  a common and synchronized counter for all CPU cores (which
+	  is useful for SMP).
diff --git a/drivers/timer/Kconfig.cc13x2_cc26x2_rtc b/drivers/timer/Kconfig.cc13x2_cc26x2_rtc
new file mode 100644
index 0000000000..f0cfacb17d
--- /dev/null
+++ b/drivers/timer/Kconfig.cc13x2_cc26x2_rtc
@@ -0,0 +1,14 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config CC13X2_CC26X2_RTC_TIMER
+	bool "TI SimpleLink CC13x2/CC26x2 RTC timer"
+	depends on SOC_SERIES_CC13X2_CC26X2
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for the TI SimpleLink
+	  CC13X2_CC26X2 series Real Time Counter and provides the standard
+	  "system clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.cortex_m_systick b/drivers/timer/Kconfig.cortex_m_systick
new file mode 100644
index 0000000000..358109b244
--- /dev/null
+++ b/drivers/timer/Kconfig.cortex_m_systick
@@ -0,0 +1,21 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+DT_COMPAT_ARM_V6M_SYSTICK := arm,armv6m-systick
+DT_COMPAT_ARM_V7M_SYSTICK := arm,armv7m-systick
+DT_COMPAT_ARM_V8M_SYSTICK := arm,armv8m-systick
+DT_COMPAT_ARM_V8_1M_SYSTICK := arm,armv8.1m-systick
+
+config CORTEX_M_SYSTICK
+	bool "Cortex-M SYSTICK timer"
+	depends on CPU_CORTEX_M_HAS_SYSTICK
+	default $(dt_compat_enabled,$(DT_COMPAT_ARM_V6M_SYSTICK)) || \
+		$(dt_compat_enabled,$(DT_COMPAT_ARM_V7M_SYSTICK)) || \
+		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8M_SYSTICK)) || \
+		$(dt_compat_enabled,$(DT_COMPAT_ARM_V8_1M_SYSTICK))
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the Cortex-M processor
+	  SYSTICK timer and provides the standard "system clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.esp32c3_sys b/drivers/timer/Kconfig.esp32c3_sys
new file mode 100644
index 0000000000..8bf5580c52
--- /dev/null
+++ b/drivers/timer/Kconfig.esp32c3_sys
@@ -0,0 +1,14 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config ESP32C3_SYS_TIMER
+	bool "ESP32C3 sys-timer support"
+	depends on SOC_ESP32C3
+	default y
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This option enables the system timer driver for the Espressif ESP32C3
+	  and provides the standard "system clock driver" interface.
diff --git a/drivers/timer/Kconfig.hpet b/drivers/timer/Kconfig.hpet
new file mode 100644
index 0000000000..08afcc2dfa
--- /dev/null
+++ b/drivers/timer/Kconfig.hpet
@@ -0,0 +1,15 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config HPET_TIMER
+	bool "HPET timer"
+	select IOAPIC if X86
+	select LOAPIC if X86
+	imply TIMER_READS_ITS_FREQUENCY_AT_RUNTIME
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This option selects High Precision Event Timer (HPET) as a
+	  system timer.
diff --git a/drivers/timer/Kconfig.ite_it8xxx2 b/drivers/timer/Kconfig.ite_it8xxx2
new file mode 100644
index 0000000000..fa57602072
--- /dev/null
+++ b/drivers/timer/Kconfig.ite_it8xxx2
@@ -0,0 +1,12 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config ITE_IT8XXX2_TIMER
+	bool "ITE it8xxx2 timer driver"
+	depends on SOC_IT8XXX2
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the ITE it8xxx2
+	  HW timer model
diff --git a/drivers/timer/Kconfig.leon_gptimer b/drivers/timer/Kconfig.leon_gptimer
new file mode 100644
index 0000000000..96e10b1308
--- /dev/null
+++ b/drivers/timer/Kconfig.leon_gptimer
@@ -0,0 +1,12 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config LEON_GPTIMER
+	bool "LEON timer"
+	depends on SOC_SPARC_LEON
+	select DYNAMIC_INTERRUPTS
+	help
+	  This module implements a kernel device driver for the GRLIB
+	  GPTIMER which is common in LEON systems.
diff --git a/drivers/timer/Kconfig.litex b/drivers/timer/Kconfig.litex
new file mode 100644
index 0000000000..80e2574928
--- /dev/null
+++ b/drivers/timer/Kconfig.litex
@@ -0,0 +1,12 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config LITEX_TIMER
+	bool "LiteX Timer"
+	default y
+	depends on SOC_RISCV32_LITEX_VEXRISCV
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for LiteX Timer.
diff --git a/drivers/timer/Kconfig.mchp_xec_rtos b/drivers/timer/Kconfig.mchp_xec_rtos
new file mode 100644
index 0000000000..4c348483d9
--- /dev/null
+++ b/drivers/timer/Kconfig.mchp_xec_rtos
@@ -0,0 +1,13 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config MCHP_XEC_RTOS_TIMER
+	bool "Microchip XEC series RTOS timer"
+	depends on SOC_FAMILY_MEC
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the Microchip
+	  XEC series RTOS timer and provides the standard "system clock
+	  driver" interfaces.
diff --git a/drivers/timer/Kconfig.mcux_lptmr b/drivers/timer/Kconfig.mcux_lptmr
new file mode 100644
index 0000000000..d72983dd36
--- /dev/null
+++ b/drivers/timer/Kconfig.mcux_lptmr
@@ -0,0 +1,12 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config MCUX_LPTMR_TIMER
+	bool "MCUX LPTMR timer"
+	depends on HAS_MCUX_LPTMR && !COUNTER_MCUX_LPTMR
+	help
+	  This module implements a kernel device driver for the NXP MCUX Low
+	  Power Timer (LPTMR) and provides the standard "system clock driver"
+	  interfaces.
diff --git a/drivers/timer/Kconfig.mcux_os b/drivers/timer/Kconfig.mcux_os
new file mode 100644
index 0000000000..d61df48187
--- /dev/null
+++ b/drivers/timer/Kconfig.mcux_os
@@ -0,0 +1,15 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+DT_COMPAT_NXP_OS_TIMER := nxp,os-timer
+
+config MCUX_OS_TIMER
+	bool "MCUX OS Event timer"
+	depends on HAS_MCUX_OS_TIMER
+	default $(dt_compat_enabled,$(DT_COMPAT_NXP_OS_TIMER))
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the NXP OS
+	  event timer and provides the standard "system clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.native_posix b/drivers/timer/Kconfig.native_posix
new file mode 100644
index 0000000000..72962d3f8b
--- /dev/null
+++ b/drivers/timer/Kconfig.native_posix
@@ -0,0 +1,14 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config NATIVE_POSIX_TIMER
+	bool "(POSIX) native_posix timer driver"
+	default y
+	depends on BOARD_NATIVE_POSIX
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for the native_posix HW timer
+	  model
diff --git a/drivers/timer/Kconfig.npcx_itim b/drivers/timer/Kconfig.npcx_itim
new file mode 100644
index 0000000000..f9dce5923e
--- /dev/null
+++ b/drivers/timer/Kconfig.npcx_itim
@@ -0,0 +1,15 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config NPCX_ITIM_TIMER
+	bool "Nuvoton NPCX series internal 64/32-bit timers"
+	default y
+	depends on SOC_FAMILY_NPCX
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for the Nuvoton NPCX
+	  series internal 64/32-bit timers and provides the standard "system
+	  clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.nrf_rtc b/drivers/timer/Kconfig.nrf_rtc
new file mode 100644
index 0000000000..4b9690ca25
--- /dev/null
+++ b/drivers/timer/Kconfig.nrf_rtc
@@ -0,0 +1,57 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config NRF_RTC_TIMER
+	bool "nRF Real Time Counter (NRF_RTC1) Timer"
+	depends on CLOCK_CONTROL
+	depends on SOC_COMPATIBLE_NRF
+	select TICKLESS_CAPABLE
+	select NRF_HW_RTC1_RESERVED
+	help
+	  This module implements a kernel device driver for the nRF Real Time
+	  Counter NRF_RTC1 and provides the standard "system clock driver"
+	  interfaces.
+
+if NRF_RTC_TIMER
+
+config NRF_RTC_TIMER_USER_CHAN_COUNT
+	int "Additional channels that can be used"
+	default 0
+	help
+	  Use nrf_rtc_timer.h API. Driver is not managing allocation of channels.
+
+choice
+	prompt "Clock startup policy"
+	default SYSTEM_CLOCK_WAIT_FOR_STABILITY
+
+config SYSTEM_CLOCK_NO_WAIT
+	bool "No wait"
+	help
+	  System clock source is initiated but does not wait for clock readiness.
+	  When this option is picked, system clock may not be ready when code relying
+	  on kernel API is executed. Requested timeouts will be prolonged by the
+	  remaining startup time.
+
+config SYSTEM_CLOCK_WAIT_FOR_AVAILABILITY
+	bool "Wait for availability"
+	help
+	  System clock source initialization waits until clock is available. In some
+	  systems, clock initially runs from less accurate source which has faster
+	  startup time and then seamlessly switches to the target clock source when
+	  it is ready. When this option is picked, system clock is available after
+	  system clock driver initialization but it may be less accurate. Option is
+	  equivalent to waiting for stability if clock source does not have
+	  intermediate state.
+
+config SYSTEM_CLOCK_WAIT_FOR_STABILITY
+	bool "Wait for stability"
+	help
+	  System clock source initialization waits until clock is stable. When this
+	  option is picked, system clock is available and stable after system clock
+	  driver initialization.
+
+endchoice
+
+endif # NRF_RTC_TIMER
diff --git a/drivers/timer/Kconfig.rcar_cmt b/drivers/timer/Kconfig.rcar_cmt
new file mode 100644
index 0000000000..999aa3f7d2
--- /dev/null
+++ b/drivers/timer/Kconfig.rcar_cmt
@@ -0,0 +1,13 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config RCAR_CMT_TIMER
+	bool "Renesas RCar cmt timer"
+	default y
+	depends on SOC_SERIES_RCAR_GEN3
+	help
+	  This module implements a kernel device driver for the Renesas RCAR
+	  platform provides the standard "system clock driver" interfaces.
+	  If unchecked, no timer will be used.
diff --git a/drivers/timer/Kconfig.riscv_machine b/drivers/timer/Kconfig.riscv_machine
new file mode 100644
index 0000000000..37547d3ed1
--- /dev/null
+++ b/drivers/timer/Kconfig.riscv_machine
@@ -0,0 +1,13 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config RISCV_MACHINE_TIMER
+	bool "RISCV Machine Timer"
+	depends on SOC_FAMILY_RISCV_PRIVILEGE
+	select TICKLESS_CAPABLE
+	select TIMER_HAS_64BIT_CYCLE_COUNTER
+	help
+	  This module implements a kernel device driver for the generic RISCV machine
+	  timer driver. It provides the standard "system clock driver" interfaces.
diff --git a/drivers/timer/Kconfig.rv32m1_lptmr b/drivers/timer/Kconfig.rv32m1_lptmr
new file mode 100644
index 0000000000..d46e73e952
--- /dev/null
+++ b/drivers/timer/Kconfig.rv32m1_lptmr
@@ -0,0 +1,14 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config RV32M1_LPTMR_TIMER
+	bool "RV32M1 LPTMR system timer driver"
+	default y
+	depends on SOC_OPENISA_RV32M1_RISCV32
+	depends on RV32M1_INTMUX
+	help
+	  This module implements a kernel device driver for using the LPTMR
+	  peripheral as the system clock. It provides the standard "system clock
+	  driver" interfaces.
diff --git a/drivers/timer/Kconfig.sam0_rtc b/drivers/timer/Kconfig.sam0_rtc
new file mode 100644
index 0000000000..4650ac676a
--- /dev/null
+++ b/drivers/timer/Kconfig.sam0_rtc
@@ -0,0 +1,13 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config SAM0_RTC_TIMER
+	bool "Atmel SAM0 series RTC timer"
+	depends on SOC_FAMILY_SAM0
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the Atmel SAM0
+	  series Real Time Counter and provides the standard "system clock
+	  driver" interfaces.
diff --git a/drivers/timer/Kconfig.xlnx_psttc b/drivers/timer/Kconfig.xlnx_psttc
new file mode 100644
index 0000000000..657cee8673
--- /dev/null
+++ b/drivers/timer/Kconfig.xlnx_psttc
@@ -0,0 +1,22 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config XLNX_PSTTC_TIMER
+	bool "Xilinx PS ttc timer support"
+	default y
+	depends on SOC_XILINX_ZYNQMP
+	select TICKLESS_CAPABLE
+	help
+	  This module implements a kernel device driver for the Xilinx ZynqMP
+	  platform provides the standard "system clock driver" interfaces.
+	  If unchecked, no timer will be used.
+
+config XLNX_PSTTC_TIMER_INDEX
+	int "Xilinx PS ttc timer index"
+	range 0 3
+	default 0
+	depends on XLNX_PSTTC_TIMER
+	help
+	  This is the index of TTC timer picked to provide system clock.
diff --git a/drivers/timer/Kconfig.xtensa b/drivers/timer/Kconfig.xtensa
new file mode 100644
index 0000000000..bef218a8b6
--- /dev/null
+++ b/drivers/timer/Kconfig.xtensa
@@ -0,0 +1,26 @@
+# Copyright (c) 2014-2015 Wind River Systems, Inc.
+# Copyright (c) 2016 Cadence Design Systems, Inc.
+# Copyright (c) 2019 Intel Corp.
+# SPDX-License-Identifier: Apache-2.0
+
+config XTENSA_TIMER
+	bool "Xtensa timer support"
+	depends on XTENSA
+	default y
+	select TICKLESS_CAPABLE
+	help
+	  Enables a system timer driver for Xtensa based on the CCOUNT
+	  and CCOMPARE special registers.
+
+config XTENSA_TIMER_ID
+	int "System timer CCOMPAREn register index"
+	default 1
+	depends on XTENSA_TIMER
+	help
+	  Index of the CCOMPARE register (and associated interrupt)
+	  used for the system timer.  Xtensa CPUs have hard-configured
+	  interrupt priorities associated with each timer, and some of
+	  them can be unmaskable (and thus not usable by OS code that
+	  need synchronization, like the timer subsystem!).  Choose
+	  carefully.  Generally you want the timer with the highest
+	  priority maskable interrupt.