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