Hi, Alan, > > > And, for Xilinx's EHCI host controller with built-in TT, we do not have > > any registers for special management of TT buffers. Since Xilinx's EHCI > > host controller can be configured as HS only or HS/FS (which will have > > TT), so we have a flag to show whether TT is in the hardware or not. > > Software therefore can set the has_tt flag. In hardware, the host > > controller is also aware of whether TT is built in. In the case when TT > > is there, and if the directly connected device is FS (which enables TT), > > then traffic is filtered by the TT. In the case if the HS control > > transfer is a clear_tt_buffer, TT will clear its TT buffers. > > What HS control transfer? usbcore never sends control transfers or > interrupt transfers to the root hub. Instead it calls > ehci_hub_control() or ehci_hub_status_data(). > That is right. The traffic that TT is filtering is the traffic from the root hub to devices. > > I wonder whether it is possible to add in a flag, such as > > tt_support_clear_tt_buffer, which is default to be off. And if it is on, > > then clear_tt_buffer can be sent to the root hub? > > You have to explain more clearly how the Xilinx controller expects to > receive these messages. > I am not sure whether it is possible. But a control message of HUB_CLEAR_TT_BUFFER is expected to clear the tt buffers inside TT for a particular endpoint, just like the one in hub_clear_tt_buffer(). My understanding is that this message will be addressed to the root hub, however, it will go through the TT, and get executed there. > Alan Stern > Thanks, Julie. This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
