Public bug reported:

It has been observed that sometimes it is not possible to pair with
BLE remote devices when the host system is using combo (WiFi + BT)
chip.

The root cause of the disconnection has been identified as coming from
the internal to bluez timeout. If bluez does not hear any reply from for
two seconds the link is automagically disconnected. The reason fro the
silence is not however a failure of the remote device but quite often a
delay in the WiFi/BT combo driver that causes the packages not to reach
the bluez stack.

[Impact]

Not possible to pair BLE remote devices such as sensors and such with
Ubuntu when the host system uses BT+WiFi combo SoC. The connection
attempt is disturbed with a timeout.

[Fix]

It has been fixed by increasing the timeout value from 2 seconds to
4 seconds. It is enough for the events to reach the stack (measured
that it takes between 3 and 3.5 seconds).

[Testcase]

Tested with the device that failed to connect to Ubuntu Core gateway.
It fails w/o the patch, it connects just fine with the patch applied.

[Regression Potential]

Very small. The increased timeout is taken into consideration only for
new and scan report triggered connections. It will not make any already
working device to fail to pair.

[Other Info]

The bug has been discussed and fixed here:

https://marc.info/?l=linux-bluetooth&m=150824844606937&w=2

[Patch]

https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-
next.git/commit/?id=1f01d8be0e6a04bd682a55f6d50c14c1679e7571

The patch has been accepted by the upstream and will be a part of the next
kernel release. Currently in the bluetooth-next tree.

** Affects: bluez (Ubuntu)
     Importance: Undecided
     Assignee: Konrad Zapałowicz (kzapalowicz)
         Status: In Progress

** Attachment added: 
"0001-bluetooth-increase-timeout-for-le-auto-connections.patch"
   
https://bugs.launchpad.net/bugs/1731467/+attachment/5006899/+files/0001-bluetooth-increase-timeout-for-le-auto-connections.patch

** Changed in: bluez (Ubuntu)
       Status: New => In Progress

** Changed in: bluez (Ubuntu)
     Assignee: (unassigned) => Konrad Zapałowicz (kzapalowicz)

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https://bugs.launchpad.net/bugs/1731467

Title:
  Cannot pair BLE remote devices when using combo BT SoC

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