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Merge branch 'usb-next' into musb-merge
* usb-next: (132 commits) USB: uas: Use GFP_NOIO instead of GFP_KERNEL in I/O submission path USB: uas: Ensure we only bind to a UAS interface USB: uas: Rename sense pipe and sense urb to status pipe and status urb USB: uas: Use kzalloc instead of kmalloc USB: uas: Fix up the Sense IU usb: musb: core: kill unneeded #include's DA8xx: assign name to MUSB IRQ resource usb: gadget: g_ncm added usb: gadget: f_ncm.c added usb: gadget: u_ether: prepare for NCM usb: pch_udc: Fix setup transfers with data out usb: pch_udc: Fix compile error, warnings and checkpatch warnings usb: add ab8500 usb transceiver driver USB: gadget: Implement runtime PM for MSM bus glue driver USB: gadget: Implement runtime PM for ci13xxx gadget USB: gadget: Add USB controller driver for MSM SoC USB: gadget: Introduce ci13xxx_udc_driver struct USB: gadget: Initialize ci13xxx gadget device's coherent DMA mask USB: gadget: Fix "scheduling while atomic" bugs in ci13xxx_udc USB: gadget: Separate out PCI bus code from ci13xxx_udc ...
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Original file line number | Diff line number | Diff line change |
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@@ -2,7 +2,7 @@ | |
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Alan Stern <[email protected]> | ||
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December 11, 2009 | ||
October 28, 2010 | ||
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@@ -107,9 +107,14 @@ allowed to issue dynamic suspends. | |
The user interface for controlling dynamic PM is located in the power/ | ||
subdirectory of each USB device's sysfs directory, that is, in | ||
/sys/bus/usb/devices/.../power/ where "..." is the device's ID. The | ||
relevant attribute files are: wakeup, control, and autosuspend. | ||
(There may also be a file named "level"; this file was deprecated | ||
as of the 2.6.35 kernel and replaced by the "control" file.) | ||
relevant attribute files are: wakeup, control, and | ||
autosuspend_delay_ms. (There may also be a file named "level"; this | ||
file was deprecated as of the 2.6.35 kernel and replaced by the | ||
"control" file. In 2.6.38 the "autosuspend" file will be deprecated | ||
and replaced by the "autosuspend_delay_ms" file. The only difference | ||
is that the newer file expresses the delay in milliseconds whereas the | ||
older file uses seconds. Confusingly, both files are present in 2.6.37 | ||
but only "autosuspend" works.) | ||
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power/wakeup | ||
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@@ -140,33 +145,36 @@ as of the 2.6.35 kernel and replaced by the "control" file.) | |
suspended and autoresume was not allowed. This | ||
setting is no longer supported.) | ||
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power/autosuspend | ||
power/autosuspend_delay_ms | ||
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This file contains an integer value, which is the | ||
number of seconds the device should remain idle before | ||
the kernel will autosuspend it (the idle-delay time). | ||
The default is 2. 0 means to autosuspend as soon as | ||
the device becomes idle, and negative values mean | ||
never to autosuspend. You can write a number to the | ||
file to change the autosuspend idle-delay time. | ||
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Writing "-1" to power/autosuspend and writing "on" to power/control do | ||
essentially the same thing -- they both prevent the device from being | ||
autosuspended. Yes, this is a redundancy in the API. | ||
number of milliseconds the device should remain idle | ||
before the kernel will autosuspend it (the idle-delay | ||
time). The default is 2000. 0 means to autosuspend | ||
as soon as the device becomes idle, and negative | ||
values mean never to autosuspend. You can write a | ||
number to the file to change the autosuspend | ||
idle-delay time. | ||
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Writing "-1" to power/autosuspend_delay_ms and writing "on" to | ||
power/control do essentially the same thing -- they both prevent the | ||
device from being autosuspended. Yes, this is a redundancy in the | ||
API. | ||
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(In 2.6.21 writing "0" to power/autosuspend would prevent the device | ||
from being autosuspended; the behavior was changed in 2.6.22. The | ||
power/autosuspend attribute did not exist prior to 2.6.21, and the | ||
power/level attribute did not exist prior to 2.6.22. power/control | ||
was added in 2.6.34.) | ||
was added in 2.6.34, and power/autosuspend_delay_ms was added in | ||
2.6.37 but did not become functional until 2.6.38.) | ||
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Changing the default idle-delay time | ||
------------------------------------ | ||
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The default autosuspend idle-delay time is controlled by a module | ||
parameter in usbcore. You can specify the value when usbcore is | ||
loaded. For example, to set it to 5 seconds instead of 2 you would | ||
The default autosuspend idle-delay time (in seconds) is controlled by | ||
a module parameter in usbcore. You can specify the value when usbcore | ||
is loaded. For example, to set it to 5 seconds instead of 2 you would | ||
do: | ||
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modprobe usbcore autosuspend=5 | ||
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@@ -234,25 +242,23 @@ every device. | |
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If a driver knows that its device has proper suspend/resume support, | ||
it can enable autosuspend all by itself. For example, the video | ||
driver for a laptop's webcam might do this, since these devices are | ||
rarely used and so should normally be autosuspended. | ||
driver for a laptop's webcam might do this (in recent kernels they | ||
do), since these devices are rarely used and so should normally be | ||
autosuspended. | ||
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Sometimes it turns out that even when a device does work okay with | ||
autosuspend there are still problems. For example, there are | ||
experimental patches adding autosuspend support to the usbhid driver, | ||
which manages keyboards and mice, among other things. Tests with a | ||
number of keyboards showed that typing on a suspended keyboard, while | ||
causing the keyboard to do a remote wakeup all right, would | ||
nonetheless frequently result in lost keystrokes. Tests with mice | ||
showed that some of them would issue a remote-wakeup request in | ||
response to button presses but not to motion, and some in response to | ||
neither. | ||
autosuspend there are still problems. For example, the usbhid driver, | ||
which manages keyboards and mice, has autosuspend support. Tests with | ||
a number of keyboards show that typing on a suspended keyboard, while | ||
causing the keyboard to do a remote wakeup all right, will nonetheless | ||
frequently result in lost keystrokes. Tests with mice show that some | ||
of them will issue a remote-wakeup request in response to button | ||
presses but not to motion, and some in response to neither. | ||
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The kernel will not prevent you from enabling autosuspend on devices | ||
that can't handle it. It is even possible in theory to damage a | ||
device by suspending it at the wrong time -- for example, suspending a | ||
USB hard disk might cause it to spin down without parking the heads. | ||
(Highly unlikely, but possible.) Take care. | ||
device by suspending it at the wrong time. (Highly unlikely, but | ||
possible.) Take care. | ||
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The driver interface for Power Management | ||
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@@ -336,10 +342,6 @@ autosuspend the interface's device. When the usage counter is = 0 | |
then the interface is considered to be idle, and the kernel may | ||
autosuspend the device. | ||
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(There is a similar usage counter field in struct usb_device, | ||
associated with the device itself rather than any of its interfaces. | ||
This counter is used only by the USB core.) | ||
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Drivers need not be concerned about balancing changes to the usage | ||
counter; the USB core will undo any remaining "get"s when a driver | ||
is unbound from its interface. As a corollary, drivers must not call | ||
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@@ -409,11 +411,11 @@ during autosuspend. For example, there's not much point | |
autosuspending a keyboard if the user can't cause the keyboard to do a | ||
remote wakeup by typing on it. If the driver sets | ||
intf->needs_remote_wakeup to 1, the kernel won't autosuspend the | ||
device if remote wakeup isn't available or has been disabled through | ||
the power/wakeup attribute. (If the device is already autosuspended, | ||
though, setting this flag won't cause the kernel to autoresume it. | ||
Normally a driver would set this flag in its probe method, at which | ||
time the device is guaranteed not to be autosuspended.) | ||
device if remote wakeup isn't available. (If the device is already | ||
autosuspended, though, setting this flag won't cause the kernel to | ||
autoresume it. Normally a driver would set this flag in its probe | ||
method, at which time the device is guaranteed not to be | ||
autosuspended.) | ||
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If a driver does its I/O asynchronously in interrupt context, it | ||
should call usb_autopm_get_interface_async() before starting output and | ||
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@@ -422,20 +424,19 @@ it receives an input event, it should call | |
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usb_mark_last_busy(struct usb_device *udev); | ||
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in the event handler. This sets udev->last_busy to the current time. | ||
udev->last_busy is the field used for idle-delay calculations; | ||
updating it will cause any pending autosuspend to be moved back. Most | ||
of the usb_autopm_* routines will also set the last_busy field to the | ||
current time. | ||
in the event handler. This tells the PM core that the device was just | ||
busy and therefore the next autosuspend idle-delay expiration should | ||
be pushed back. Many of the usb_autopm_* routines also make this call, | ||
so drivers need to worry only when interrupt-driven input arrives. | ||
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Asynchronous operation is always subject to races. For example, a | ||
driver may call one of the usb_autopm_*_interface_async() routines at | ||
a time when the core has just finished deciding the device has been | ||
idle for long enough but not yet gotten around to calling the driver's | ||
suspend method. The suspend method must be responsible for | ||
synchronizing with the output request routine and the URB completion | ||
handler; it should cause autosuspends to fail with -EBUSY if the | ||
driver needs to use the device. | ||
driver may call the usb_autopm_get_interface_async() routine at a time | ||
when the core has just finished deciding the device has been idle for | ||
long enough but not yet gotten around to calling the driver's suspend | ||
method. The suspend method must be responsible for synchronizing with | ||
the I/O request routine and the URB completion handler; it should | ||
cause autosuspends to fail with -EBUSY if the driver needs to use the | ||
device. | ||
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External suspend calls should never be allowed to fail in this way, | ||
only autosuspend calls. The driver can tell them apart by checking | ||
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@@ -472,7 +473,9 @@ Firstly, a device may already be autosuspended when a system suspend | |
occurs. Since system suspends are supposed to be as transparent as | ||
possible, the device should remain suspended following the system | ||
resume. But this theory may not work out well in practice; over time | ||
the kernel's behavior in this regard has changed. | ||
the kernel's behavior in this regard has changed. As of 2.6.37 the | ||
policy is to resume all devices during a system resume and let them | ||
handle their own runtime suspends afterward. | ||
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Secondly, a dynamic power-management event may occur as a system | ||
suspend is underway. The window for this is short, since system | ||
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