USB 2.0 specification chapter 11.17.5 says "as part of endpoint halt processing for full-/low-speed endpoints connected via a TT, the host software must use the Clear_TT_Buffer request to the TT to ensure that the buffer is not in the busy state".
In our case, a full-speed speaker (ConferenceCam) is behind a high- speed hub (ConferenceCam Connect), sometimes once we get STALL on a request we may continue to get STALL with the folllowing requests, like Set_Interface. Solution is to invoke usb_hub_clear_tt_buffer() to send Clear_TT_Buffer request to the hub of the device for the following Set_Interface requests to the device to get ACK successfully. The Clear_TT_Buffer request sent to the hub includes the address of the LS/FS child device in wValue field. usb_hub_clear_tt_buffer() uses udev->devnum to set the address wValue. This won't work for devices connected to xHC. For other host controllers udev->devnum is the same as the address of the usb device, chosen and set by usb core. With xHC the controller hardware assigns the address, and won't be the same as devnum. Here we have two patches. One is to add devaddr in struct usb_device for usb_hub_clear_tt_buffer() to use. Another is to invoke usb_hub_clear_tt_buffer() for halt processing. Signed-off-by: Jim Lin <ji...@nvidia.com> Jim Lin (2): usb: Add devaddr in struct usb_device usb: xhci: Add Clear_TT_Buffer drivers/usb/core/hub.c | 4 +++- drivers/usb/host/xhci-ring.c | 27 ++++++++++++++++++++++++++- drivers/usb/host/xhci.c | 23 +++++++++++++++++++++++ drivers/usb/host/xhci.h | 5 +++++ include/linux/usb.h | 2 ++ 5 files changed, 59 insertions(+), 2 deletions(-) -- 2.1.4
