Dear kernel developers, I'm running into an interesting limitation with a NEC PD720200 USB 3.0 host controller connected by PCIe. What I want to do is connect 13 mass storage devices to each downstream port (of which there are two). For this I have a collection of Anker 13-port hubs containing 4 VIA VL812-B2 4-port hub controllers, daisy chained on the last port. Everything is fine until I've plugged in 20 of the usb-sticks, at which point I seem to run out of some resource. In my syslog I can read [ 6112.316240] xhci_hcd 0000:04:00.0: Error while assigning device slot ID [ 6112.316247] hub 7-2.4:1.0: couldn't allocate port 1 usb_device whenever xhci_hcd tries to enumerate additional devices. In my head this amounts to 24 devices (16 sticks + 8 hub controllers) on the 2-port root hub, which seems a bit short of the USB spec. I have tried this combination of adapter card and hubs on the current 3.14-rc8 kernel in addition to the stock ubuntu 3.11.0-12-generic with same results. Attached is my syslog when successfully connecting the final high-speed stick into 7-2.3 followed by the failing enumeration of device 7-2.4.1 at time [ 6112.316240]. Even with dynamic debug set for the xhci_hcd module I can't seem to get a more specific reason for the failure to assign the device slot id. I grepped the error messages, leading me to xhci_alloc_dev, but without being familiar with the usb host drivers I am not able to see why the host controller is not assigning any more device slots. Could someone point me to the right place for me to look further? -- Amund Hov +47 412 96 298 amund.hov@xxxxxxxxxx This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or may constitute as attorney work product. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, notify us immediately by telephone and destroy this message if a facsimile or (ii) delete this message immediately if this is an electronic communication. Thank you.
Attachment:
syslog_excerpt_enumeration_fail
Description: syslog_excerpt_enumeration_fail
