linux-stable.git/drivers/usb/core/sysfs.c, branch linux-3.13.y

usb: Don't enable USB 2.0 Link PM by default.

2013-10-16T19:24:19+00:00

How it's supposed to work:
--------------------------

USB 2.0 Link PM is a lower power state that some newer USB 2.0 devices
support.  USB 3.0 devices certified by the USB-IF are required to
support it if they are plugged into a USB 2.0 only port, or a USB 2.0
cable is used.  USB 2.0 Link PM requires both a USB device and a host
controller that supports USB 2.0 hardware-enabled LPM.

USB 2.0 Link PM is designed to be enabled once by software, and the host
hardware handles transitions to the L1 state automatically.  The premise
of USB 2.0 Link PM is to be able to put the device into a lower power
link state when the bus is idle or the device NAKs USB IN transfers for
a specified amount of time.

...but hardware is broken:
--------------------------

It turns out many USB 3.0 devices claim to support USB 2.0 Link PM (by
setting the LPM bit in their USB 2.0 BOS descriptor), but they don't
actually implement it correctly.  This manifests as the USB device
refusing to respond to transfers when it is plugged into a USB 2.0 only
port under the Haswell-ULT/Lynx Point LP xHCI host.

These devices pass the xHCI driver's simple test to enable USB 2.0 Link
PM, wait for the port to enter L1, and then bring it back into L0.  They
only start to break when L1 entry is interleaved with transfers.

Some devices then fail to respond to the next control transfer (usually
a Set Configuration).  This results in devices never enumerating.

Other mass storage devices (such as a later model Western Digital My
Passport USB 3.0 hard drive) respond fine to going into L1 between
control transfers.  They ACK the entry, come out of L1 when the host
needs to send a control transfer, and respond properly to those control
transfers.  However, when the first READ10 SCSI command is sent, the
device NAKs the data phase while it's reading from the spinning disk.
Eventually, the host requests to put the link into L1, and the device
ACKs that request.  Then it never responds to the data phase of the
READ10 command.  This results in not being able to read from the drive.

Some mass storage devices (like the Corsair Survivor USB 3.0 flash
drive) are well behaved.  They ACK the entry into L1 during control
transfers, and when SCSI commands start coming in, they NAK the requests
to go into L1, because they need to be at full power.

Not all USB 3.0 devices advertise USB 2.0 link PM support.  My Point
Grey USB 3.0 webcam advertises itself as a USB 2.1 device, but doesn't
have a USB 2.0 BOS descriptor, so we don't enable USB 2.0 Link PM.  I
suspect that means the device isn't certified.

What do we do about it?
-----------------------

There's really no good way for the kernel to test these devices.
Therefore, the kernel needs to disable USB 2.0 Link PM by default, and
distros will have to enable it by writing 1 to the sysfs file
/sys/bus/usb/devices/../power/usb2_hardware_lpm.  Rip out the xHCI Link
PM test, since it's not sufficient to detect these buggy devices, and
don't automatically enable LPM after the device is addressed.

This patch should be backported to kernels as old as 3.11, that
contain the commit a558ccdcc71c7770c5e80c926a31cfe8a3892a09 "usb: xhci:
add USB2 Link power management BESL support".  Without this fix, some
USB 3.0 devices will not enumerate or work properly under USB 2.0 ports
on Haswell-ULT systems.

Signed-off-by: Sarah Sharp 
Cc: stable@vger.kernel.org

drivers: usb: core: {file,hub,sysfs,usb}.c: Whitespace fixes

2013-10-12T00:02:37+00:00

including:

- removing of trailing whitespace
- removing spaces before array indexing (foo [] to foo[])
- reindention of a switch-case block
- spaces to tabs

Signed-off-by: Matthias Beyer 
Signed-off-by: Greg Kroah-Hartman

USB: fix substandard locking for the sysfs files

2013-09-26T00:27:01+00:00

This patch straightens out some locking issues in the USB sysfs
interface:

	Deauthorization will destroy existing configurations.
	Attributes that read from udev->actconfig need to lock the
	device to prevent races.  Likewise for the rawdescriptor
	values.

	Attributes that access an interface's current alternate
	setting should use ACCESS_ONCE() to obtain the cur_altsetting
	pointer, to protect against concurrent altsetting changes.

	The supports_autosuspend() attribute routine accesses values
	from an interface's driver, so it should lock the interface
	(rather than the usb_device) to protect against concurrent
	unbinds.  Once this is done, the routine can be simplified
	considerably.

Scalar values that are stored directly in the usb_device structure are
always available.  They do not require any locking.  The same is true
of the cached interface string descriptor, because it is not
deallocated until the usb_host_interface structure is destroyed.

Signed-off-by: Alan Stern 
CC: Hans de Goede 
Signed-off-by: Greg Kroah-Hartman

USB: core: be specific about attribute permissions

2013-08-25T22:12:03+00:00

Instead of having to audit all sysfs attributes, to ensure we get them
right, use the default macros the driver core provides us (read-only,
read-write) to make the code simpler, and to prevent any mistakes from
ever happening.

Signed-off-by: Greg Kroah-Hartman

usb: add usb2 Link PM variables to sysfs and usb_device

2013-06-05T23:48:40+00:00

Adds abitilty to tune L1 timeout (inactivity timer for usb2 link sleep)
and BESL (best effort service latency)via sysfs.

This also adds a new usb2_lpm_parameters structure with those variables to
struct usb_device.

Signed-off-by: Mathias Nyman 
Signed-off-by: Sarah Sharp

USB: remove CONFIG_USB_SUSPEND option

2013-03-28T18:10:22+00:00

This patch (as1675) removes the CONFIG_USB_SUSPEND option, essentially
replacing it everywhere with CONFIG_PM_RUNTIME (except for one place
in hub.c, where it is replaced with CONFIG_PM because the code needs
to be used in both runtime and system PM).  The net result is code
shrinkage and simplification.

There's very little point in keeping CONFIG_USB_SUSPEND because almost
everybody enables it.  The few that don't will find that the usbcore
module has gotten somewhat bigger and they will have to take active
measures if they want to prevent hubs from being runtime suspended.

Signed-off-by: Alan Stern 
CC: Peter Chen 
Signed-off-by: Greg Kroah-Hartman

usb/core: consider link speed while looking at bMaxPower

2013-01-12T00:16:01+00:00

The USB 2.0 specification says that bMaxPower is the maximum power
consumption expressed in 2 mA units and the USB 3.0 specification says
that it is expressed in 8 mA units.
This patch adds a helper function usb_get_max_power() which computes the
value based on config & usb_device's speed value. The the device descriptor
dump computes the value on its own.

Cc: Sarah Sharp 
Cc: Greg Kroah-Hartman 
Acked-by: Alan Stern 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Greg Kroah-Hartman

usb: convert USB_QUIRK_RESET_MORPHS to USB_QUIRK_RESET

2012-08-20T21:38:08+00:00

Since the attribute avoid_reset_quirk is work for all devices including
those devices that can't morph, convert USB_QUIRK_RESET_MORPHS to
USB_QUIRK_RESET.

Signed-off-by: Lan Tianyu 
Signed-off-by: Greg Kroah-Hartman

usb: Rename temp variable "config" to "val" in the set_avoid_reset_quirk()

2012-08-10T19:06:39+00:00

In USB, the word "config" already has aseparate meaning. So it will
cause confusion if use "config" as variable's name for other purposes.
This patch is to convert the "config"  to "val"

Acked-by: Alan Stern 
Signed-off-by: Lan Tianyu 
Signed-off-by: Greg Kroah-Hartman

USB: Add a sysfs file to show LTM capabilities.

2012-07-11T11:06:48+00:00

USB 3.0 devices can optionally support Latency Tolerance Messaging
(LTM).  Add a new sysfs file in the device directory to show whether a
device is LTM capable.  This file will be present for both USB 2.0 and
USB 3.0 devices.

Signed-off-by: Sarah Sharp