Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: > On Thu, 4 Jul 2013, Bjørn Mork wrote: > >> > It may be that the device simply takes longer to resume than it should. >> > Or longer than btusb expects it to, which may not be the same thing. >> >> Yes, that is what it looks like. But the URBs are submitted as part of >> the resume callback. Shouldn't the device be alive and kicking when >> this is called? At least from the USB point of view, which is all the >> driver can possibly know anything about? Is the problem that the >> firmware finishes the USB resume before actually being ready to respond >> to the HCI command? > > I don't know. The USB spec gives devices 10 ms to recover during a > resume; after that they are supposed to be ready to operate normally. > This delay is already built into usbcore and it is visible in your > usbmon trace. > > There is one notable difference between your failure and success > traces. Failure: > >> ffff88021ace62c0 3675041611 S Co:002:00 s 20 00 0000 0000 0003 3 = 011000 >> ffff88022228d140 3675041721 S Co:002:00 s 01 0b 0000 0001 0000 0 >> ffff88021ace62c0 3675042361 C Co:002:00 0 3 > >> ffff88022228d140 3675042409 C Co:002:00 0 0 >> ffff88020c40f380 3675043359 C Ii:002:01 0 6 = 0f040101 010b >> ffff88020c40f380 3675043429 S Ii:002:01 -115 64 < > > Success: > >> ffff88020c40f200 88163963 S Co:002:00 s 20 00 0000 0000 0003 3 = 011000 >> ffff88020c752980 88165215 C Ii:002:01 0 14 = 0e0c0101 10000600 05060200 0005 >> ffff88020c752980 88165281 S Ii:002:01 -115 64 < >> ffff88020c40f200 88165327 C Co:002:00 0 3 > > > In the failure case, a Set-Interface request gets sent before the > interrupt URB completes. Maybe that accounts for the unexpected > behavior. Maybe. But the device does send a message which translates as a valid HCI message, so it looks like everything is OK up to and including the USB layer. I tried to figure out the exact meaning of that message, but that's not straight forward unless you are familiar with the Bluetooth specs. Which I'm certainly not. What I did find out is only what the HCI debug code also could tell me: 0f - HCI_EV_CMD_STATUS 04 - length: 4 01 - status: 1 01 - ncmds: 1 010b - opcode: 0x0b01 Enabling the dynamic debugging in hci_core and hci_event makes this clear, along with the fact that HCI core ignores this event: Jul 5 12:27:21 nemi kernel: [44750.608222] btusb_tx_complete:574: hci1 urb ffff880231a10c00 status 0 count 3 Jul 5 12:27:21 nemi kernel: [44750.609223] btusb_intr_complete:281: hci1 urb ffff880231a109c0 status 0 count 6 Jul 5 12:27:21 nemi kernel: [44750.609297] hci_rx_work:3463: hci1 Jul 5 12:27:21 nemi kernel: [44750.609346] hci_rx_work:3492: hci1 Event packet Jul 5 12:27:21 nemi kernel: [44750.609361] hci_cmd_status_evt:2418: hci1 opcode 0x0b01 Jul 5 12:27:21 nemi kernel: [44750.609371] hci_req_cmd_complete:3406: opcode 0x0b01 status 0x01 Jul 5 12:27:21 nemi kernel: [44750.609641] hci_dev_get:691: 1 The "hci_cmd_status_evt" message shows that we hit the default do-nothing handler for events unknown to hci_event.c. For some reason this cancels the command timer: if (opcode != HCI_OP_NOP) del_timer(&hdev->cmd_timer); But changing that only leads to the timer expiring ang logging Jul 5 12:27:23 nemi kernel: [44752.532142] Bluetooth: hci1 command 0x1001 tx timeout Jul 5 12:27:23 nemi kernel: [44752.532233] hci_cmd_work:3519: hci1 cmd_cnt 1 cmd queued 0 a few seconds later (0x1001 is HCI_OP_READ_LOCAL_VERSION, so that's the command we're waiting for). Proper handling of the 0x0b01 event is most likely required to continue here. I do assume the device means to signal something by sending that 0x0b01 event, and based on the observed behaviour and existing code I guess that something translates to "not ready yet - please resend last command" or similar. But I haven't been able to find any definition of that event anywhere, so this is based on pure speculation. Anyway, unless someone from the Bluetooth list shouts out, then I am going to conclude that the device, USB core and btusb all behave correctly, but that waking up this device (and likely other recent devices) can fail because the HCI core fails to handle a link state event it should handle. I don't have any proposed fix, except ugly hacks to let the device have some more time. So I am hoping someone knowing Bluetooth will come up with better ideas. Bjørn -- 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
