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25cd2882e2
The xHCI driver currently uses a USB core internal field,
udev->lpm_capable, to indicate the xHCI driver knows how to calculate
the LPM timeout values. If this value is set for the host controller
udev, it means Link PM can be enabled for child devices under that host.
Change the code so the xHCI driver isn't mucking with USB core internal
fields. Instead, indicate the xHCI driver doesn't support Link PM on
this host by clearing the U1 and U2 exit latencies in the roothub
SuperSpeed Extended Capabilities BOS descriptor.
The code to check for the roothub setting U1 and U2 exit latencies to
zero will also disable LPM for external devices that do that same. This
was already effectively done with commit
ae8963adb4 "usb: Don't enable LPM if the
exit latency is zero." Leave that code in place, so that if a device
sets one exit latency value to zero, but the other is set to a valid
value, LPM is only enabled for the U1 or U2 state that had the valid
value. This is the same behavior the code had before.
Also, change messages about missing Link PM information from warning
level to info level. Only print a warning about the first device that
doesn't support LPM, to avoid log spam. Further, cleanup some
unnecessary line breaks to help people to grep for the error messages.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.