Lines Matching +full:usb2 +full:- +full:lpm +full:- +full:disable
1 .. _usb-power-management:
7 :Date: Last-updated: February 2014
11 ---------
17 * Changing the default idle-delay time
31 -------------------------
35 component is ``suspended`` it is in a nonfunctional low-power state; it
37 ``resumed`` (returned to a functional full-power state) when the kernel
67 ----------------------
85 --------------------------
101 -------------------
106 of time, the so-called idle-delay time.
118 usblp, usblcd, and usb-skeleton (which doesn't count). If a
119 non-supporting driver is bound to a device, the device won't be
134 ---------------------------------
165 - ``on`` means that the device should be resumed and
169 - ``auto`` is the normal state in which the kernel is
181 before the kernel will autosuspend it (the idle-delay
186 idle-delay time.
188 Writing ``-1`` to ``power/autosuspend_delay_ms`` and writing ``on`` to
189 ``power/control`` do essentially the same thing -- they both prevent the
201 Changing the default idle-delay time
202 ------------------------------------
204 The default autosuspend idle-delay time (in seconds) is controlled by
233 then each new USB device will have its autosuspend idle-delay
234 initialized to 5. (The idle-delay values for already existing devices
237 Setting the initial default idle-delay to -1 will prevent any
243 --------
255 than hubs. Hubs, at least, appear to be reasonably well-behaved in
262 This means that non-hub devices won't be autosuspended unless the user
268 also change the idle-delay time; 2 seconds is not the best choice for
283 of them will issue a remote-wakeup request in response to button
293 -----------------------------------------
305 - The ``suspend`` method is called to warn the driver that the
311 - The ``resume`` method is called to tell the driver that the
315 - The ``reset_resume`` method is called to tell the driver that
327 possible to work around the hibernation-forces-disconnect problem by
331 :ref:`usb-persist`) and it can also be used under certain
350 ---------------------------------------------------
379 has returned -- say from within a work-queue routine -- provided they
395 their non-async counterparts. The big difference is that they
417 carry out the operation automatically when the autosuspend idle-delay
422 autosuspend, there's no idle-delay for an autoresume.
426 -----------------------------------
435 drivers can disable autosuspend by calling::
445 ``intf->needs_remote_wakeup`` to 1, the kernel won't autosuspend the
460 busy and therefore the next autosuspend idle-delay expiration should
462 so drivers need to worry only when interrupt-driven input arrives.
470 cause autosuspends to fail with -EBUSY if the driver needs to use the
481 ----------------
483 For external events -- but not necessarily for autosuspend or
484 autoresume -- the device semaphore (udev->dev.sem) will be held when a
499 --------------------------------------------
512 Secondly, a dynamic power-management event may occur as a system
515 For example, a suspended device may send a remote-wakeup signal while
525 ---------------------
527 xHCI host controller provides hardware link power management to usb2.0
529 enabling hardware LPM, the host can automatically put the device into
530 lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices),
533 The user interface for controlling hardware LPM is located in the
540 When a USB2 device which support LPM is plugged to a
541 xHCI host root hub which support software LPM, the
542 host will run a software LPM test for it; if the device
544 supports USB2 hardware LPM, this file will show up and
545 driver will enable hardware LPM for the device. You
546 can write y/Y/1 or n/N/0 to the file to enable/disable
547 USB2 hardware LPM manually. This is for test purpose mainly.
552 When a USB 3.0 lpm-capable device is plugged in to a
556 supports USB3 hardware LPM, USB3 hardware LPM will be
558 The files hold a string value (enable or disable)
559 indicating whether or not USB3 hardware LPM U1 or U2
563 ----------------------
567 capability to disable power to ports under some conditions. Power is
569 In the case of a root or platform-internal hub the host controller
597 http://dl.dropbox.com/u/96820575/sarah-sharp-lpt-port-power-off2-mini.pdf
601 http://linuxplumbers.ubicast.tv/videos/usb-port-power-off-kerneluserspace-api/
613 -------------------------------------
631 lost and all attached child-devices will disconnect. A good rule of thumb is
639 prefix=/sys/devices/pci0000:00/0000:00:14.0/usb3/3-1
645 $prefix/3-1:1.0/3-1-port1/device
647 $prefix/3-1:1.0/3-1-port1/power/pm_qos_no_power_off
648 $prefix/3-1:1.0/3-1-port1/device/power/control
649 $prefix/3-1:1.0/3-1-port1/device/3-1.1:<intf0>/driver/unbind
650 $prefix/3-1:1.0/3-1-port1/device/3-1.1:<intf1>/driver/unbind
652 $prefix/3-1:1.0/3-1-port1/device/3-1.1:<intfN>/driver/unbind
656 hi-speed peer::
658 $prefix/3-1:1.0/3-1-port1/peer -> ../../../../usb2/2-1/2-1:1.0/2-1-port1
659 ../../../../usb2/2-1/2-1:1.0/2-1-port1/peer -> ../../../../usb3/3-1/3-1:1.0/3-1-port1
662 peer ports are simply the hi-speed and superspeed interface pins that
667 connection and attempt to connect to the hi-speed pins. The
670 1. Port suspend is sequenced to guarantee that hi-speed ports are powered-off
671 before their superspeed peer is permitted to power-off. The implication is
673 not cause the port to power-off until its highspeed peer has gone to its
675 if it wants to guarantee that a superspeed port will power-off.
677 2. Port resume is sequenced to force a superspeed port to power-on prior to its
684 child device can suspend (autosuspend-delay) and resume (reset-resume
689 ``<hubdev-portX>/power/pm_qos_no_power_off``:
697 ``<hubdev-portX>/power/runtime_status``:
702 ``<hubdev-portX>/connect_type``:
703 An advisory read-only flag to userspace indicating the
729 powered-off at all times.
738 - since we are relying on the BIOS to get this ACPI
742 - Take care in clearing ``pm_qos_no_power_off``. Once
758 power session loss (suspend / port-power event). When
764 this time the only mechanism to clear the usb-internal
765 wakeup-capability for an interface device is to unbind
768 Summary of poweroff pre-requisite settings relative to a port device::
777 -------------------------------------
793 all ports (set ``<hubdev-portX>/power/pm_qos_no_power_off`` to ``0``) when
796 ports when the screen blanks, and re-power them when the screen becomes