On 7/17/20 9:59 AM, Marcel Holtmann wrote:
>>>> The MediaTek Bluetooth platform (MT6630 etc.) has a peculiar implementation
>>>> for the eSCO/SCO connection via BT/EDR: the host controller returns error
>>>> code 0x20 (LMP feature not supported) for HCI_Setup_Synchronous_Connection
>>>> (0x0028) command without actually trying to setup connection with a remote
>>>> device in case such device (like Digma BT-14 headset) didn't advertise its
>>>> supported features. Even though this doesn't break compatibility with the
>>>> Bluetooth standard it breaks the compatibility with the Hands-Free Profile
>>>> (HFP).
>>>>
>>>> This patch returns the compatibility with the HFP profile and actually
>>>> tries to check all available connection parameters despite of the specific
>>>> MediaTek implementation. Without it one was unable to establish eSCO/SCO
>>>> connection with some headsets.
>>>
>>> please include the parts of btmon output that show this issue.
>>
>> Funny, I had removed that part from the original patch. Here's that log:
>>
>> < HCI Command: Setup Synchronous Connection (0x01|0x0028) plen 17 #1 [hci0] 6.705320
>> Handle: 50
>> Transmit bandwidth: 8000
>> Receive bandwidth: 8000
>> Max latency: 10
>> Setting: 0x0060
>> Input Coding: Linear
>> Input Data Format: 2's complement
>> Input Sample Size: 16-bit
>> of bits padding at MSB: 0
>> Air Coding Format: CVSD
>> Retransmission effort: Optimize for power consumption (0x01)
>> Packet type: 0x0380
>> 3-EV3 may not be used
>> 2-EV5 may not be used
>> 3-EV5 may not be used
>>> HCI Event: Command Status (0x0f) plen 4 #2 [hci0] 6.719598
>> Setup Synchronous Connection (0x01|0x0028) ncmd 1
>> Status: Unsupported LMP Parameter Value / Unsupported LL Parameter Value (0x20)
> I double check with the specification and it is not precise that errors should be reported
> via sync conn complete events. My assumption would be that your headset only supports SCO and
> thus the controller realizes that eSCO request can not be completed anyway. So the controller
> opts for quickest path to get out of this.
>>>> Based on the patch by Ildar Kamaletdinov <i.kamaletdinov@xxxxxxxxxxxx>.
Adding him to CC...
>>>>
>>>> Signed-off-by: Sergey Shtylyov <s.shtylyov@xxxxxxxxxxxx>
>>>>
>>>> ---
>>>> This patch is against the 'bluetooth-next.git' repo.
>>>>
>>>> net/bluetooth/hci_event.c | 8 ++++++++
>>>> 1 file changed, 8 insertions(+)
>>>>
>>>> Index: bluetooth-next/net/bluetooth/hci_event.c
>>>> ===================================================================
>>>> --- bluetooth-next.orig/net/bluetooth/hci_event.c
>>>> +++ bluetooth-next/net/bluetooth/hci_event.c
>>>> @@ -2187,6 +2187,13 @@ static void hci_cs_setup_sync_conn(struc
>>>> if (acl) {
>>>> sco = acl->link;
>>>> if (sco) {
>>>> + if (status == 0x20 && /* Unsupported LMP Parameter value */
>>>> + sco->out) {
Actually, I was expecting that you'd tell me to create a HCI quirk for this situation.
I have a patch doing that but I haven't been able to locate the driver in which to set this
quirk flag...
>>>> + sco->pkt_type = (hdev->esco_type & SCO_ESCO_MASK) |
>>>> + (hdev->esco_type & EDR_ESCO_MASK);
>>>> + if (hci_setup_sync(sco, sco->link->handle))
>>>> + goto unlock;
>>>> + }
>>>> sco->state = BT_CLOSED;
>>>
>>> since this is the command status event, I doubt that sco->out check is needed.
>>
>> Can't comment oin this, my BT fu is too weak...
> It is the case. Command status is only local to command we issued and thus in this case it
> is the connection creation attempt from our side. Meaning it is always outgoing.
Ildar, what do you think?
> Regards
>
> Marcel
MBR, Sergei
