On Thu, 27 Jun 2013, William Gulland wrote:
> Control transfers have both IN and OUT (or SETUP) packets, so when
> clearing TT buffers for a control transfer it's necessary to send
> two HUB_CLEAR_TT_BUFFER requests to the hub.
>
> Signed-off-by: William Gulland <wgull...@google.com>
> ---
> drivers/usb/core/hub.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index feef935..868ad74 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -668,6 +668,15 @@ resubmit:
> static inline int
> hub_clear_tt_buffer (struct usb_device *hdev, u16 devinfo, u16 tt)
> {
> + /* Need to clear both directions for control ep */
> + if (((devinfo >> 11) & USB_ENDPOINT_XFERTYPE_MASK) ==
> + USB_ENDPOINT_XFER_CONTROL) {
> + int status = usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
> + HUB_CLEAR_TT_BUFFER, USB_RT_PORT,
> + devinfo ^ 0x8000, tt, NULL, 0, 1000);
> + if (status)
> + return status;
> + }
> return usb_control_msg(hdev, usb_sndctrlpipe(hdev, 0),
> HUB_CLEAR_TT_BUFFER, USB_RT_PORT, devinfo,
> tt, NULL, 0, 1000);
Well, this won't hurt much. And since it does seem to fix a hardware
problem,
Acked-by: Alan Stern <st...@rowland.harvard.edu>
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