Return-Path: Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.0 \(1816\)) Subject: Re: [RFC] Bluetooth: Set ISOC altsetting from within notify callback From: Marcel Holtmann In-Reply-To: <526FAC6C.1090306@timomueller.eu> Date: Tue, 29 Oct 2013 13:53:29 +0100 Cc: "linux-bluetooth@vger.kernel.org development" Message-Id: <3DCF3537-8249-4560-AA95-9513159425B1@holtmann.org> References: <1380952305-14104-1-git-send-email-marcel@holtmann.org> <5257EB7A.7010407@timomueller.eu> <525BB77A.7030803@timomueller.eu> <526FAC6C.1090306@timomueller.eu> To: =?windows-1252?Q?Timo_M=FCller?= Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Timo, >>>>> Since the event handling is done within a workqueue, the notify >>>>> callback can now sleep. So no need to trigger a separate workqueue >>>>> from within the Bluetooth USB driver. >>>>> >>>>> This should give a little bit better latency with the SCO packet >>>>> processing since the ISOC altsetting is correct from the beginning. >>>>> >>>>> However I am not sure if we can actually sleep in the USB reset >>>>> handler and what we need to do to restore the correct altsetting >>>>> in there. This could potentially fail, so please test ;) >>>>> >>>>> Signed-off-by: Marcel Holtmann >>>>> --- >>>>> drivers/bluetooth/btusb.c | 34 ++++++++++++++-------------------- >>>>> 1 file changed, 14 insertions(+), 20 deletions(-) >>>>> >>>>> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c >>>>> index f3dfc0a..32cae73 100644 >>>>> --- a/drivers/bluetooth/btusb.c >>>>> +++ b/drivers/bluetooth/btusb.c >>>>> @@ -245,7 +245,6 @@ struct btusb_data { >>>>> >>>>> unsigned long flags; >>>>> >>>>> - struct work_struct work; >>>>> struct work_struct waker; >>>>> >>>>> struct usb_anchor tx_anchor; >>>>> @@ -685,7 +684,6 @@ static int btusb_close(struct hci_dev *hdev) >>>>> if (!test_and_clear_bit(HCI_RUNNING, &hdev->flags)) >>>>> return 0; >>>>> >>>>> - cancel_work_sync(&data->work); >>>>> cancel_work_sync(&data->waker); >>>>> >>>>> clear_bit(BTUSB_ISOC_RUNNING, &data->flags); >>>>> @@ -827,18 +825,6 @@ done: >>>>> return err; >>>>> } >>>>> >>>>> -static void btusb_notify(struct hci_dev *hdev, unsigned int evt) >>>>> -{ >>>>> - struct btusb_data *data = hci_get_drvdata(hdev); >>>>> - >>>>> - BT_DBG("%s evt %d", hdev->name, evt); >>>>> - >>>>> - if (hdev->conn_hash.sco_num != data->sco_num) { >>>>> - data->sco_num = hdev->conn_hash.sco_num; >>>>> - schedule_work(&data->work); >>>>> - } >>>>> -} >>>>> - >>>>> static inline int __set_isoc_interface(struct hci_dev *hdev, int >>>>> altsetting) >>>>> { >>>>> struct btusb_data *data = hci_get_drvdata(hdev); >>>>> @@ -882,9 +868,8 @@ static inline int __set_isoc_interface(struct >>>>> hci_dev *hdev, int altsetting) >>>>> return 0; >>>>> } >>>>> >>>>> -static void btusb_work(struct work_struct *work) >>>>> +static void btusb_update_isoc_altsetting(struct btusb_data *data) >>>>> { >>>>> - struct btusb_data *data = container_of(work, struct btusb_data, >>>>> work); >>>>> struct hci_dev *hdev = data->hdev; >>>>> int new_alts; >>>>> int err; >>>>> @@ -932,6 +917,18 @@ static void btusb_work(struct work_struct *work) >>>>> } >>>>> } >>>>> >>>>> +static void btusb_notify(struct hci_dev *hdev, unsigned int evt) >>>>> +{ >>>>> + struct btusb_data *data = hci_get_drvdata(hdev); >>>>> + >>>>> + BT_DBG("%s evt %d", hdev->name, evt); >>>>> + >>>>> + if (hdev->conn_hash.sco_num != data->sco_num) { >>>>> + data->sco_num = hdev->conn_hash.sco_num; >>>>> + btusb_update_isoc_altsetting(data); >>>>> + } >>>>> +} >>>>> + >>>>> static void btusb_waker(struct work_struct *work) >>>>> { >>>>> struct btusb_data *data = container_of(work, struct >>>>> btusb_data, waker); >>>>> @@ -1404,7 +1401,6 @@ static int btusb_probe(struct usb_interface >>>>> *intf, >>>>> >>>>> spin_lock_init(&data->lock); >>>>> >>>>> - INIT_WORK(&data->work, btusb_work); >>>>> INIT_WORK(&data->waker, btusb_waker); >>>>> spin_lock_init(&data->txlock); >>>>> >>>>> @@ -1540,8 +1536,6 @@ static int btusb_suspend(struct usb_interface >>>>> *intf, pm_message_t message) >>>>> return -EBUSY; >>>>> } >>>>> >>>>> - cancel_work_sync(&data->work); >>>>> - >>>>> btusb_stop_traffic(data); >>>>> usb_kill_anchored_urbs(&data->tx_anchor); >>>>> >>>>> @@ -1606,8 +1600,8 @@ static int btusb_resume(struct usb_interface >>>>> *intf) >>>>> play_deferred(data); >>>>> clear_bit(BTUSB_SUSPENDING, &data->flags); >>>>> spin_unlock_irq(&data->txlock); >>>>> - schedule_work(&data->work); >>>>> >>>>> + btusb_update_isoc_altsetting(data); >>>>> return 0; >>>>> >>>>> failed: >>>>> >>>> I have been testing this patch for the last two days at the UPF in >>>> Vienna. It was running fine most of the time, but I experienced two >>>> crashes. Both crashes appeared when there was an active call and the >>>> phone transferred audio to the phone and back. Both times I wasn't >>>> able to reproduce, when I restarted everything and tested again it >>>> worked fine. >>>> >>>> Unfortunately the kernel log is not complete but, when it failed the >>>> kernel reported: >>>> [147.344546] Bluetooth: hci0 SCO packet for unknown connection handle 5 >>>> [147.354515] Bluetooth: hci0 SCO packet for unknown connection handle 21 >>>> [147.354537] Bluetooth: hci0 SCO packet for unknown connection handle 29 >>>> [147.354548] Bluetooth: hci0 SCO packet for unknown connection handle >>>> 65534 >>>> [147.364574] Bluetooth: hci0 SCO packet for unknown connection handle >>>> 65532 >>>> [147.364581] Bluetooth: hci0 SCO packet for unknown connection handle 27 >>>> ? >>> what kind of hardware where you testing with? >> >> It was nothing special, an off-the-shelf CSR USB BT Dongle. >> >>> >>> This handle mismatch normally means that our SCO packet frames are out >>> of sync. I think we are not doing a good job trying to keep them >>> nicely lined up. >>> >>> For the crash, do you happen to have a backtrace of the crash. >>> Personally I was worried about the reset handling and not the actual >>> alternate setting switching. >> >> Unfortunately I haven't. To be precise the first crash wasn't even a >> crash, as everything was continuing to run, but without a working audio >> of course. The second time my system completely froze, but due to my >> fault I wasn't able to pull the backtrace. I'll see if I can reproduce >> this week and send a backtrace if I manage to. > > I've been unsuccessfully trying to reproduce the system crash with an iPhone 3 and a Nexus 4. Routing the Audio to the phone and back occasionally leads to the observed handle mismatches, but no crashes/freezes whatsoever. Sometimes the mismatch is even recovered. we could start more than 2 ISOC URBs and see if that improves the behavior. However at the end of the day, we might just have to deal with the fact that with ISOC URBs, we sometimes loose a few bytes. So btusb.ko needs to re-sync by itself. My wild guess is that HFP 1.5 in most of the cases we just got lucky that the stream of PCM data is pretty constant. And once throwing HFP 1.6 and mSBC into the mix these problem manifest itself. Then again, my main concern with this patch is the reset and resume handling. I have no idea if the URB allocation is correct there. One other thing we could be doing is that we tell the driver first to switch the alternate endpoints before even establishing the eSCO connection. That might bring this a lot better into sync as well. We would still then need to filter out the packets for unknown handles since their might be some. One problem however might be that we not always know ahead of time what kind of voice setting we actually get. Regards Marcel