• Mathias Nyman's avatar
    xhci: Solve full event ring by increasing TRBS_PER_SEGMENT to 256 · 697409c7
    Mathias Nyman authored
    commit 18cc2f4c upstream.
    
    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
    Signed-off-by: default avatarMathias Nyman <mathias.nyman@linux.intel.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    697409c7
xhci.h 64.6 KB