Re: [PATCH 0/2] Quirk to enable QCA9377 to discover BLE devices

["João Paulo Rechi Vita" <jprvita@gmail.com>]

Hello Marcel, thanks for the quick response.

On Wed, Apr 24, 2019 at 12:17 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Joao Paulo,
>
> > As reported previously on [1], it is currently not possible to discover
> > BLE devices with QCA9377 controllers. When trying to start an active
> > scanning procedure with this controller, three commands are queued,
> > LE_SET_RANDOM_ADDR, LE_SET_SCAN_PARAM and LE_SET_SCAN_ENABLE. After the
> > first command is sent to the controller, a command complete event for it
> > is received, and the second command is sent, an extra command complete
> > for the first command is received. At this point the kernel sends the
> > next command and fails to process the command complete event for the
> > LE_SET_SCAN_PARAM command, because when it arrives it does not match the
> > last command that was sent. This makes hdev->le_scan_type never be
> > updated and the kernel behaves as if a passive scanning procedure was
> > being performed, thus no device found events are sent to userspace.
> >
> > [1] https://www.spinics.net/lists/linux-bluetooth/msg79102.html
> >
> > I have received no replies on the previous report and on further
> > attempts to contact the QCA addresses that have submitted Bluetooth
> > firmware blobs to linux-firmware upstream. This series avoids the
> > problem described above, but I believe ideally the controller should not
> > be sending this extra command complete event.
> >
> > I'm not 100% sure if the approach taken here is the best way to work
> > around this problem in the kernel, as I am not super familiar with the
> > HCI layer. I'll be happy to hear suggestions of better approaches.
> >
> > Full logs from btmon can be found bellow this message, and the extra
> > command complete event can be seen at timestamp 27.420131.
>
> so can we get a fixed firmware from Qualcomm? Or at least some ROM patches for it?
>

That was my initial expectation as well -- maybe you can show the
problem to some Qualcomm contacts?

> > Best regards,
> >
> > João Paulo Rechi Vita (2):
> >  Bluetooth: Create new HCI_QUIRK_WAIT_FOR_MATCHING_CC
> >  Bluetooth: Set HCI_QUIRK_WAIT_FOR_MATCHING_CC for QCA9377
> >
> > drivers/bluetooth/btusb.c        | 9 +++++++++
> > include/net/bluetooth/hci.h      | 4 ++++
> > include/net/bluetooth/hci_core.h | 1 +
> > net/bluetooth/hci_core.c         | 3 +++
> > net/bluetooth/hci_event.c        | 4 ++++
> > 5 files changed, 21 insertions(+)
> >
> > --
> > 2.20.1
> >
> > Bluetooth monitor ver 5.50
> > = Note: Linux version 5.0.0+ (x86_64)                                  0.352340
> > = Note: Bluetooth subsystem version 2.22                               0.352343
> > = New Index: 80:C5:F2:8F:87:84 (Primary,USB,hci0)               [hci0] 0.352344
> > = Open Index: 80:C5:F2:8F:87:84                                 [hci0] 0.352345
> > = Index Info: 80:C5:F2:8F:87:84 (Qualcomm)                      [hci0] 0.352346
> > @ MGMT Open: bluetoothd (privileged) version 1.14             {0x0001} 0.352347
> > @ MGMT Open: btmon (privileged) version 1.14                  {0x0002} 0.352366
> > @ MGMT Open: btmgmt (privileged) version 1.14                {0x0003} 27.302164
> > @ MGMT Command: Start Discovery (0x0023) plen 1       {0x0003} [hci0] 27.302310
> >        Address type: 0x06
> >          LE Public
> >          LE Random
> > < HCI Command: LE Set Random Address (0x08|0x0005) plen 6   #1 [hci0] 27.302496
> >        Address: 15:60:F2:91:B2:24 (Non-Resolvable)
> >> HCI Event: Command Complete (0x0e) plen 4                 #2 [hci0] 27.419117
> >      LE Set Random Address (0x08|0x0005) ncmd 1
> >        Status: Success (0x00)
> > < HCI Command: LE Set Scan Parameters (0x08|0x000b) plen 7  #3 [hci0] 27.419244
> >        Type: Active (0x01)
> >        Interval: 11.250 msec (0x0012)
> >        Window: 11.250 msec (0x0012)
> >        Own address type: Random (0x01)
> >        Filter policy: Accept all advertisement (0x00)
> >> HCI Event: Command Complete (0x0e) plen 4                 #4 [hci0] 27.420131
> >      LE Set Random Address (0x08|0x0005) ncmd 1
> >        Status: Success (0x00)
>
> so we really need to ignore this command complete and not start ahead with the next command. Especially since we really only support one command at a time right now.
>

Agreed.

> > < HCI Command: LE Set Scan Enable (0x08|0x000c) plen 2      #5 [hci0] 27.420259
> >        Scanning: Enabled (0x01)
> >        Filter duplicates: Enabled (0x01)
> >> HCI Event: Command Complete (0x0e) plen 4                 #6 [hci0] 27.420969
> >      LE Set Scan Parameters (0x08|0x000b) ncmd 1
> >        Status: Success (0x00)
>
> We need for this command complete to arrive and only then continue with LE Set Scan Enable. We don’t need a quirk for it. Just add support for dealing with unexpected command complete opcodes. And print a big error if that happens.
>

Makes sense, I'm sending an updated version ignoring unexpected CC
events on all hardware. Looking at the code it seems the only
exception is a CC event for HCI_OP_RESET on some CSR controllers,
which is handled in hci_req_cmd_complete, so I'm letting that flow
through.

--
João Paulo Rechi Vita
http://about.me/jprvita