forked from Minki/linux
85dc0b8a40
A runtime suspend of a device (e.g. an MMC controller) belonging to a power domain or, in a more complicated scenario, a runtime suspend of another device in the same power domain, may cause power to be removed from the entire domain. In that case, the amount of time necessary to runtime-resume the given device (e.g. the MMC controller) is often substantially greater than the time needed to run its driver's runtime resume callback. That may hurt performance in some situations, because user data may need to wait for the device to become operational, so we should make it possible to prevent that from happening. For this reason, introduce a new sysfs attribute for devices, power/pm_qos_resume_latency_us, allowing user space to specify the upper bound of the time necessary to bring the (runtime-suspended) device up after the resume of it has been requested. However, make that attribute appear only for the devices whose drivers declare support for it by calling the (new) dev_pm_qos_expose_latency_limit() helper function with the appropriate initial value of the attribute. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Reviewed-by: Kevin Hilman <khilman@ti.com> Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Acked-by: Linus Walleij <linus.walleij@linaro.org>
186 lines
7.5 KiB
Plaintext
186 lines
7.5 KiB
Plaintext
What: /sys/devices/.../power/
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Date: January 2009
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../power directory contains attributes
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allowing the user space to check and modify some power
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management related properties of given device.
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What: /sys/devices/.../power/wakeup
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Date: January 2009
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../power/wakeup attribute allows the user
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space to check if the device is enabled to wake up the system
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from sleep states, such as the memory sleep state (suspend to
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RAM) and hibernation (suspend to disk), and to enable or disable
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it to do that as desired.
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Some devices support "wakeup" events, which are hardware signals
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used to activate the system from a sleep state. Such devices
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have one of the following two values for the sysfs power/wakeup
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file:
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+ "enabled\n" to issue the events;
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+ "disabled\n" not to do so;
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In that cases the user space can change the setting represented
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by the contents of this file by writing either "enabled", or
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"disabled" to it.
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For the devices that are not capable of generating system wakeup
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events this file is not present. In that case the device cannot
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be enabled to wake up the system from sleep states.
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What: /sys/devices/.../power/control
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Date: January 2009
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../power/control attribute allows the user
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space to control the run-time power management of the device.
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All devices have one of the following two values for the
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power/control file:
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+ "auto\n" to allow the device to be power managed at run time;
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+ "on\n" to prevent the device from being power managed;
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The default for all devices is "auto", which means that they may
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be subject to automatic power management, depending on their
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drivers. Changing this attribute to "on" prevents the driver
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from power managing the device at run time. Doing that while
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the device is suspended causes it to be woken up.
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What: /sys/devices/.../power/async
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Date: January 2009
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../async attribute allows the user space to
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enable or diasble the device's suspend and resume callbacks to
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be executed asynchronously (ie. in separate threads, in parallel
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with the main suspend/resume thread) during system-wide power
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transitions (eg. suspend to RAM, hibernation).
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All devices have one of the following two values for the
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power/async file:
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+ "enabled\n" to permit the asynchronous suspend/resume;
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+ "disabled\n" to forbid it;
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The value of this attribute may be changed by writing either
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"enabled", or "disabled" to it.
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It generally is unsafe to permit the asynchronous suspend/resume
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of a device unless it is certain that all of the PM dependencies
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of the device are known to the PM core. However, for some
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devices this attribute is set to "enabled" by bus type code or
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device drivers and in that cases it should be safe to leave the
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default value.
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What: /sys/devices/.../power/wakeup_count
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_count attribute contains the number
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of signaled wakeup events associated with the device. This
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attribute is read-only. If the device is not enabled to wake up
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the system from sleep states, this attribute is not present.
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What: /sys/devices/.../power/wakeup_active_count
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_active_count attribute contains the
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number of times the processing of wakeup events associated with
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the device was completed (at the kernel level). This attribute
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is read-only. If the device is not enabled to wake up the
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system from sleep states, this attribute is not present.
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What: /sys/devices/.../power/wakeup_hit_count
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_hit_count attribute contains the
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number of times the processing of a wakeup event associated with
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the device might prevent the system from entering a sleep state.
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This attribute is read-only. If the device is not enabled to
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wake up the system from sleep states, this attribute is not
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present.
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What: /sys/devices/.../power/wakeup_active
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_active attribute contains either 1,
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or 0, depending on whether or not a wakeup event associated with
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the device is being processed (1). This attribute is read-only.
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If the device is not enabled to wake up the system from sleep
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states, this attribute is not present.
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What: /sys/devices/.../power/wakeup_total_time_ms
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_total_time_ms attribute contains
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the total time of processing wakeup events associated with the
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device, in milliseconds. This attribute is read-only. If the
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device is not enabled to wake up the system from sleep states,
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this attribute is not present.
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What: /sys/devices/.../power/wakeup_max_time_ms
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_max_time_ms attribute contains
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the maximum time of processing a single wakeup event associated
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with the device, in milliseconds. This attribute is read-only.
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If the device is not enabled to wake up the system from sleep
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states, this attribute is not present.
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What: /sys/devices/.../power/wakeup_last_time_ms
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Date: September 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../wakeup_last_time_ms attribute contains
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the value of the monotonic clock corresponding to the time of
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signaling the last wakeup event associated with the device, in
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milliseconds. This attribute is read-only. If the device is
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not enabled to wake up the system from sleep states, this
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attribute is not present.
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What: /sys/devices/.../power/autosuspend_delay_ms
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Date: September 2010
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Contact: Alan Stern <stern@rowland.harvard.edu>
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Description:
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The /sys/devices/.../power/autosuspend_delay_ms attribute
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contains the autosuspend delay value (in milliseconds). Some
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drivers do not want their device to suspend as soon as it
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becomes idle at run time; they want the device to remain
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inactive for a certain minimum period of time first. That
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period is called the autosuspend delay. Negative values will
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prevent the device from being suspended at run time (similar
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to writing "on" to the power/control attribute). Values >=
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1000 will cause the autosuspend timer expiration to be rounded
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up to the nearest second.
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Not all drivers support this attribute. If it isn't supported,
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attempts to read or write it will yield I/O errors.
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What: /sys/devices/.../power/pm_qos_latency_us
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Date: March 2012
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/devices/.../power/pm_qos_resume_latency_us attribute
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contains the PM QoS resume latency limit for the given device,
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which is the maximum allowed time it can take to resume the
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device, after it has been suspended at run time, from a resume
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request to the moment the device will be ready to process I/O,
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in microseconds. If it is equal to 0, however, this means that
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the PM QoS resume latency may be arbitrary.
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Not all drivers support this attribute. If it isn't supported,
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it is not present.
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This attribute has no effect on system-wide suspend/resume and
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hibernation.
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