> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Florian Echtler > Sent: Wednesday, December 18, 2013 2:04 PM > > we've made some progress getting large SuperSpeed ISO transfers for the > new Kinect to work. As it turns out, the central issue here was which > XHCI controller the device is connected to. I have two different HCs, > one from Intel and one from NEC. According to lspci, these are: > > 00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset > Family USB xHCI Host Controller (rev 04)) > > 04:00.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host > Controller (rev 04) (prog-if 30 [XHCI]) > > The exact same code works when the device is attached to the NEC > controller (transferring 33792 bytes per ISO packet as requested), but > fails on the Intel controller (transferring only 11264 bytes, exactly > 1/3 of the requested size). > > I don't have enough background knowledge to decide if this is some sort > of hardware issue, missing hardware feature or rather related to the > XHCI driver. Can somebody suggest a direction for further investigation? What are the values from the ISO endpoint's Endpoint descriptor and SuperSpeed Endpoint Companion descriptor? If the Mult value is 2 (bits 1:0 of the Companion descriptor's bmAttributes field) and the Intel controller is treating it as 0 for some reason, that would give you 1/3 of the requested size. Or perhaps it is a throughput issue; if the bInterval is 1, then 33792 bytes every 128us is a pretty high data rate. Perhaps the Intel controller can't keep up. Do you have USB debugging enabled (CONFIG_USB_DEBUG=y) in the kernel config? With the latest kernels that should cause the xHCI driver to print debug messages to the dmesg log. In earlier kernels you also have to enable CONFIG_USB_XHCI_HCD_DEBUGGING. Do you have a USB bus analyzer? That should show you exactly what is going on. If not, maybe you can capture a usbmon trace. I don't know anything about usbmon, but Alan Stern might be able to help with that. -- Paul > > Thanks & best regards, Florian > -- > SENT FROM MY DEC VT50 TERMINAL -- 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
