Lines Matching refs:power
33 component is "suspended" it is in a nonfunctional low-power state; it
35 "resumed" (returned to a functional full-power state) when the kernel
47 covered to some extent (see Documentation/power/*.txt for more
67 by pressing a power button or opening the cover.
118 We can categorize power management events in two broad classes:
131 The user interface for controlling dynamic PM is located in the power/
133 /sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
143 power/wakeup
154 power/control
172 power/autosuspend_delay_ms
183 Writing "-1" to power/autosuspend_delay_ms and writing "on" to
184 power/control do essentially the same thing -- they both prevent the
188 (In 2.6.21 writing "0" to power/autosuspend would prevent the device
190 power/autosuspend attribute did not exist prior to 2.6.21, and the
191 power/level attribute did not exist prior to 2.6.22. power/control
192 was added in 2.6.34, and power/autosuspend_delay_ms was added in
240 The USB specification states that all USB devices must support power
249 power/control attribute is initialized to "on") for all devices other
290 The requirements for a USB driver to support external power management
404 reason or another. For example, the power/control attribute might be
425 writing "auto" to the device's power/control attribute. Likewise,
430 This is exactly the same as writing "on" to the power/control attribute.
492 Dynamic power management and system power management can interact in
503 Secondly, a dynamic power-management event may occur as a system
518 xHCI host controller provides hardware link power management to usb2.0
521 lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices),
525 power/ subdirectory of each USB device's sysfs directory, that is, in
526 /sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
529 power/usb2_hardware_lpm
540 power/usb3_hardware_lpm_u1
541 power/usb3_hardware_lpm_u2
557 controlled link power management, the USB subsystem also has the
558 capability to disable power to ports under some conditions. Power is
562 method calls to set the port power state. For more background see the
568 a shared power well causing power to remain until all ports in the gang
578 goes through during system suspend, i.e. the power session is lost. Any
580 similarly affected by a port power cycle event. For this reason the
584 [1]: http://dl.dropbox.com/u/96820575/sarah-sharp-lpt-port-power-off2-mini.pdf
585 [2]: http://linuxplumbers.ubicast.tv/videos/usb-port-power-off-kerneluserspace-api/
588 power control implementation will block poweroff attempts on that
595 The port power control mechanism uses the PM runtime system. Poweroff is
596 requested by clearing the power/pm_qos_no_power_off flag of the port device
600 This mechanism is dependent on the hub advertising port power switching in its
601 hub descriptor (wHubCharacteristics logical power switching mode field).
612 it will interfere with port power control.
614 Example of the relevant files for port power control. Note, in this example
625 $prefix/3-1:1.0/3-1-port1/power/pm_qos_no_power_off
626 $prefix/3-1:1.0/3-1-port1/device/power/control
649 before their superspeed peer is permitted to power-off. The implication is
651 the port to power-off until its highspeed peer has gone to its runtime suspend
653 guarantee that a superspeed port will power-off.
655 2/ Port resume is sequenced to force a superspeed port to power-on prior to its
659 power session is lost the device may have been removed, or need reset.
660 Resuming the child device when the parent port regains power resolves those
661 states and clamps the maximum port power cycle frequency at the rate the child
664 Sysfs files relevant for port power control:
665 <hubdev-portX>/power/pm_qos_no_power_off:
673 <hubdev-portX>/power/runtime_status:
674 This file reflects whether the port is 'active' (power is on)
717 power is off this port will
723 <child>/power/control:
725 power down until <child>/power/runtime_status
729 <child>/power/persist:
732 power session loss (suspend / port-power event). When
744 echo 0 > power/pm_qos_no_power_off
745 echo 0 > peer/power/pm_qos_no_power_off # if it exists
746 echo auto > power/control # this is the default value
747 echo auto > <child>/power/control
748 echo 1 > <child>/power/persist # this is the default value
757 power/pm_qos_no_power_off set to '1' causing ports to always remain
766 A more aggressive userspace policy is to enable USB port power off for
767 all ports (set <hubdev-portX>/power/pm_qos_no_power_off to '0') when
769 system. For example, a distro may want to enable power off all USB
770 ports when the screen blanks, and re-power them when the screen becomes
771 active. Smart phones and tablets may want to power off USB ports when
772 the user pushes the power button.