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 <sarah.a.sharp@linux.intel.com> Cc: stable@vger.kernel.org
usb_wait_anchor_empty_timeout() should wait till the completion handler has run. Both the zd1211rw driver and the uas driver (in its task mgmt) depend on the completion handler having completed when usb_wait_anchor_empty_timeout() returns, as they read state set by the completion handler after an usb_wait_anchor_empty_timeout() call. But __usb_hcd_giveback_urb() calls usb_unanchor_urb before calling the completion handler. This is necessary as the completion handler may re-submit and re-anchor the urb. But this introduces a race where the state these drivers want to read has not been set yet by the completion handler (this race is easily triggered with the uas task mgmt code). I've considered adding an anchor_count to struct urb, which would be incremented on anchor and decremented on unanchor, and then only actually do the anchor / unanchor on 0 -> 1 and 1 -> 0 transtions, combined with moving the unanchor call in hcd_giveback_urb to after calling the completion handler. But this will only work if urb's are only re-anchored to the same anchor as they were anchored to before the completion handler ran. And at least one driver re-anchors to another anchor from the completion handler (rtlwifi). So I have come up with this patch instead, which adds the ability to suspend wakeups of usb_wait_anchor_empty_timeout() waiters to the usb_anchor functionality, and uses this in __usb_hcd_giveback_urb() to delay wake-ups until the completion handler has run. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Oliver Neukum <oliver@neukum.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
And do so in a way which ensures that any fields added in the future will also get properly zero-ed. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Oliver Neukum <oliver@neukum.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The hcd-driver free_streams method can return an error, so lets properly propagate that. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Some host controllers(such as xHCI) can support building packet from discontinuous buffers, so introduce one flag and helper for this kind of host controllers, then the feature can help some applications(such as usbnet) by supporting arbitrary length of sg buffers. Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Ming Lei <ming.lei@canonical.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When building the htmldocs (in verbose mode), scripts/kernel-doc reports the following type of warnings: Warning(drivers/usb/core/usb.c:76): No description found for return value of 'usb_find_alt_setting' Fix them by: - adding some missing descriptions of return values - using "Return" sections for those descriptions Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bInterval must be within the range 1 - 16 when running at High/Super speed, and within the range 1 - 255 when running at Full/Low speed. In order to catch drivers passing a too large bInterval on Super/High speed scenarios (thus overflowing urb->interval), let's clamp() the argument to the allowed ranges. Signed-off-by: Felipe Balbi <balbi@ti.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
USB spec stats that short packet can only appear at the end of transfer. Because lost of HC(EHCI/UHCI/OHCI/...) can't build a full packet from discontinuous buffers, we introduce the limit in usb_submit_urb() to avoid such kind of bad sg buffers coming from driver. The limit might be a bit strict: - platform has iommu to do sg list mapping - some host controllers may support to build full packet from discontinuous buffers. But considered that most of HCs don't support that, and driver need work well or keep consistent on different HCs and ARCHs, we have to introduce the limit. Currently, only usbtest is reported to pass such sg buffers to HC, and other users(mass storage, usbfs) don't have the problem. We don't check it on USB wireless device, because: - wireless devices can't be attached to common USB bus(EHCI/UHCI/OHCI/...) - the max packet size of endpoint may be odd, and often can't devide 4KB which is a typical usage in usb mass storage application Reported-by: Konstantin Filatov <kfilatov@parallels.com> Reported-by: Denis V. Lunev <den@openvz.org> Cc: Felipe Balbi <balbi@ti.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The USB_MAXCHILDREN symbol is used in include/uapi/linux/usb/ch11.h, a user-mode header, even though it is defined in include/linux/usb.h, which is kernel-only. This causes compile-time errors when user programs try to #include linux/usb/ch11.h. This patch fixes the problem by moving the definition of USB_MAXCHILDREN into ch11.h. It also gets rid of unneeded parentheses. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>