• Sarah Sharp's avatar
    USB: Allow USB 3.0 ports to be disabled. · 41e7e056
    Sarah Sharp authored
    If hot and warm reset fails, or a port remains in the Compliance Mode,
    the USB core needs to be able to disable a USB 3.0 port.  Unlike USB 2.0
    ports, once the port is placed into the Disabled link state, it will not
    report any new device connects.  To get device connect notifications, we
    need to put the link into the Disabled state, and then the RxDetect
    state.
    
    The xHCI driver needs to atomically clear all change bits on USB 3.0
    port disable, so that we get Port Status Change Events for future port
    changes.  We could technically do this in the USB core instead of in the
    xHCI roothub code, since the port state machine can't advance out of the
    disabled state until we set the link state to RxDetect.  However,
    external USB 3.0 hubs don't need this code.  They are level-triggered,
    not edge-triggered like xHCI, so they will continue to send interrupt
    events when any change bit is set.  Therefore it doesn't make sense to
    put this code in the USB core.
    
    This patch is part of a series to fix several reports of infinite loops
    on device enumeration failure.  This includes John, when he boots with
    a USB 3.0 device (Roseweil eusb3 enclosure) attached to his NEC 0.96
    host controller.  The fix requires warm reset support, so it does not
    make sense to backport this patch to stable kernels without warm reset
    support.
    
    This patch should be backported to kernels as old as 3.2, contain the
    commit ID 75d7cf72 "usbcore: refine warm
    reset logic"
    Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
    Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Reported-by: default avatarJohn Covici <covici@ccs.covici.com>
    Cc: stable@vger.kernel.org
    41e7e056
hub.c 149 KB