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    Subject[PATCH] [51/99] USB: xhci - fix interval calculation for FS isoc endpoints
    Date
    2.6.35-longterm review patch.  If anyone has any objections, please let me know.

    ------------------
    From: Dmitry Torokhov <dtor@vmware.com>

    commit cd3c18ba2fac14b34d03cae111f215009735ea06 upstream.

    Full-speed isoc endpoints specify interval in exponent based form in
    frames, not microframes, so we need to adjust accordingly.

    NEC xHCI host controllers will return an error code of 0x11 if a full
    speed isochronous endpoint is added with the Interval field set to
    something less than 3 (2^3 = 8 microframes, or one frame). It is
    impossible for a full speed device to have an interval smaller than one
    frame.

    This was always an issue in the xHCI driver, but commit
    dfa49c4ad120a784ef1ff0717168aa79f55a483a "USB: xhci - fix math in
    xhci_get_endpoint_interval()" removed the clamping of the minimum value
    in the Interval field, which revealed this bug.

    This needs to be backported to stable kernels back to 2.6.31.

    Reported-by: Matt Evans <matt@ozlabs.org>
    Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
    Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: Andi Kleen <ak@linux.intel.com>

    ---
    drivers/usb/host/xhci-mem.c | 14 ++++++++++++--
    1 file changed, 12 insertions(+), 2 deletions(-)

    Index: linux-2.6.35.y/drivers/usb/host/xhci-mem.c
    ===================================================================
    --- linux-2.6.35.y.orig/drivers/usb/host/xhci-mem.c
    +++ linux-2.6.35.y/drivers/usb/host/xhci-mem.c
    @@ -974,9 +974,19 @@ static unsigned int xhci_parse_exponent_
    interval = clamp_val(ep->desc.bInterval, 1, 16) - 1;
    if (interval != ep->desc.bInterval - 1)
    dev_warn(&udev->dev,
    - "ep %#x - rounding interval to %d microframes\n",
    + "ep %#x - rounding interval to %d %sframes\n",
    ep->desc.bEndpointAddress,
    - 1 << interval);
    + 1 << interval,
    + udev->speed == USB_SPEED_FULL ? "" : "micro");
    +
    + if (udev->speed == USB_SPEED_FULL) {
    + /*
    + * Full speed isoc endpoints specify interval in frames,
    + * not microframes. We are using microframes everywhere,
    + * so adjust accordingly.
    + */
    + interval += 3; /* 1 frame = 2^3 uframes */
    + }

    return interval;
    }

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