457d437841
Some chips, that use Cortex-M SysTick as the system timer, disable a clock in a low power mode, that is the input for the SysTick e.g. STM32Fx family. It blocks enabling power management for these chips. The wake-up function doesn't work and the time measurement is lost. Add an additional IDLE timer that handles these functionality when the system is about to enter IDLE. It has to wake up the chip and update the cycle counter by time not measured by the SysTick. The IDLE timer has to support counter API (setting alarm and reading current value). Signed-off-by: Dawid Niedzwiecki <dawidn@google.com>
62 lines
2.3 KiB
Plaintext
62 lines
2.3 KiB
Plaintext
# Copyright (c) 2014-2015 Wind River Systems, Inc.
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# Copyright (c) 2016 Cadence Design Systems, Inc.
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# Copyright (c) 2019 Intel Corp.
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# SPDX-License-Identifier: Apache-2.0
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DT_CHOSEN_IDLE_TIMER := zephyr,cortex-m-idle-timer
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config CORTEX_M_SYSTICK
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bool "Cortex-M SYSTICK timer"
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depends on CPU_CORTEX_M_HAS_SYSTICK
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default y
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depends on DT_HAS_ARM_ARMV6M_SYSTICK_ENABLED || \
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DT_HAS_ARM_ARMV7M_SYSTICK_ENABLED || \
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DT_HAS_ARM_ARMV8M_SYSTICK_ENABLED || \
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DT_HAS_ARM_ARMV8_1M_SYSTICK_ENABLED
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select TICKLESS_CAPABLE
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select SYSTEM_TIMER_HAS_DISABLE_SUPPORT
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select CORTEX_M_SYSTICK_INSTALL_ISR
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help
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This module implements a kernel device driver for the Cortex-M processor
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SYSTICK timer and provides the standard "system clock driver" interfaces.
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config CORTEX_M_SYSTICK_INSTALL_ISR
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bool
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depends on CPU_CORTEX_M_HAS_SYSTICK
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help
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This option should be selected by SysTick-based drivers so that the
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sys_clock_isr() function is installed.
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config CORTEX_M_SYSTICK_64BIT_CYCLE_COUNTER
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bool "Cortex-M SYSTICK timer with sys_clock_cycle_get_64() support"
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depends on CORTEX_M_SYSTICK
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default y if (SYS_CLOCK_HW_CYCLES_PER_SEC > 60000000)
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select TIMER_HAS_64BIT_CYCLE_COUNTER
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help
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This driver, due to its limited 24-bits hardware counter, is already
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tracking a separate cycle count in software. This option make that
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count a 64-bits value to support sys_clock_cycle_get_64().
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This is cheap to do as expensive math operations (i.e. divisions)
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are performed only on counter interval values that always fit in
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32 bits.
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This is set to y by default when the hardware clock is fast enough
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to wrap sys_clock_cycle_get_32() in about a minute or less.
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config CORTEX_M_SYSTICK_IDLE_TIMER
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bool "Use an additional timer while entering IDLE"
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default $(dt_chosen_enabled,$(DT_CHOSEN_IDLE_TIMER))
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depends on COUNTER
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depends on TICKLESS_KERNEL
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help
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There are chips e.g. STMFX family that use SysTick as a system timer,
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but SysTick is not clocked in low power mode. These chips usually have
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another timer that is not stopped, but it has lower frequency e.g.
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RTC, thus it can't be used as a main system timer.
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Use the IDLE timer for timeout (wakeup) when the system is entering
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IDLE state.
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The chosen IDLE timer node has to support setting alarm from the
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counter API.
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