116 lines
4.1 KiB
Plaintext
116 lines
4.1 KiB
Plaintext
#
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# Copyright (c) 2014-2015 Wind River Systems, Inc.
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# Copyright (c) 2016 Intel Corporation
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#
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# SPDX-License-Identifier: Apache-2.0
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#
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menuconfig SYS_POWER_MANAGEMENT
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bool
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prompt "Power management"
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default n
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help
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This option enables the board to implement extra power management
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policies whenever the kernel becomes idle. The kernel informs the
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power management subsystem of the number of ticks until the next kernel
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timer is due to expire.
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if SYS_POWER_MANAGEMENT
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config SYS_POWER_LOW_POWER_STATE
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bool
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prompt "Low power state"
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default n
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depends on SYS_POWER_LOW_POWER_STATE_SUPPORTED
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help
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This option enables the kernel to interface with a power manager
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application. This permits the system to enter a custom CPU low power
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state when the kernel becomes idle. The low power state could be any of
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the CPU low power states supported by the processor. Generally the one
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saving most power.
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config SYS_POWER_DEEP_SLEEP
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bool
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prompt "Deep sleep state"
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default n
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depends on SYS_POWER_DEEP_SLEEP_SUPPORTED
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help
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This option enables the kernel to interface with a power manager
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application. This permits the system to enter a Deep sleep state
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supported by the SOC where the system clock is turned off while RAM is
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retained. This state would be entered when the kernel becomes idle for
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extended periods and would have a high wake latency. Resume would be
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from the reset vector same as cold boot. The interface allows
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restoration of states that were saved at the time of suspend.
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config DEVICE_POWER_MANAGEMENT
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bool
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prompt "Device power management"
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default n
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help
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This option enables the device power management interface. The
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interface consists of hook functions implemented by device drivers
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that get called by the power manager application when the system
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is going to suspend state or resuming from suspend state. This allows
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device drivers to do any necessary power management operations
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like turning off device clocks and peripherals. The device drivers
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may also save and restore states in these hook functions.
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config TICKLESS_IDLE
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bool
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prompt "Tickless idle"
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default y
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help
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This option suppresses periodic system clock interrupts whenever the
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kernel becomes idle. This permits the system to remain in a power
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saving state for extended periods without having to wake up to
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service each tick as it occurs.
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config TICKLESS_IDLE_THRESH
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int
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prompt "Tickless idle threshold"
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default 3
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depends on TICKLESS_IDLE
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help
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This option enables clock interrupt suppression when the kernel idles
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for only a short period of time. It specifies the minimum number of
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ticks that must occur before the next kernel timer expires in order
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for suppression to happen.
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config TICKLESS_KERNEL
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bool
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prompt "Tickless kernel"
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default n
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depends on TICKLESS_IDLE
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help
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This option enables a fully event driven kernel. Periodic system
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clock interrupt generation would be stopped at all times. This option
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requires Tickless Idle option to be enabled.
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config TICKLESS_KERNEL_TIME_UNIT_IN_MICRO_SECS
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int
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prompt "Tickless kernel time unit in micro seconds"
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default 1000
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depends on TICKLESS_KERNEL
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help
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This option makes the system clock and scheduling granularity.
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The default will be one millisecond. This option also determines
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the time unit passed in functions like _sys_soc_suspend. The
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value should be determined based what the timer hardware and driver
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can support. Specifying too small a time unit than what the overall
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system speed can support would cause scheduling errors.
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config BUSY_WAIT_USES_ALTERNATE_CLOCK
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bool
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prompt "Busy wait uses alternate clock in tickless kernel mode"
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default n
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help
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In tickless kernel mode, the system clock will be stopped when
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there are no timer events programmed. If the system clock is to
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be used to keep time e.g. to get a delta of time cycles then it
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needs to be turned on using provided APIs. Some platforms have
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alternate clocks which can be used instead. In that case this flag
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would be set to true. This flag would be checked before turning
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on the system clock in APIs that do busy wait reading clock
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cycles.
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endif
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