mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-02-01 02:17:00 -05:00
18cc2f4cbb
Our event ring consists of only one segment, and we risk filling the event ring in case we get isoc transfers with short intervals such as webcams that fill a TD every microframe (125us) With 64 TRB segment size one usb camera could fill the event ring in 8ms. A setup with several cameras and other devices can fill up the event ring as it is shared between all devices. This has occurred when uvcvideo queues 5 * 32TD URBs which then get cancelled when the video mode changes. The cancelled URBs are returned in the xhci interrupt context and blocks the interrupt handler from handling the new events. A full event ring will block xhci from scheduling traffic and affect all devices conneted to the xhci, will see errors such as Missed Service Intervals for isoc devices, and and Split transaction errors for LS/FS interrupt devices. Increasing the TRB_PER_SEGMENT will also increase the default endpoint ring size, which is welcome as for most isoc transfer we had to dynamically expand the endpoint ring anyway to be able to queue the 5 * 32TDs uvcvideo queues. The default size used to be 64 TRBs per segment Cc: <stable@vger.kernel.org> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 ("hub_wq").
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.