Broadcom BCM20709A0 does not work with HSP/HFP devices

0b05:17cb ASUSTek Computer, Inc. Broadcom BCM20702A0 Bluetooth

I have a USB Bluetooth dongle from ASUS based on the fairly common Broadcom BCM20702A0 chipset.

I can pair bluetooth audio device to this and have tried a JabraSpeak 510 Bluetooth Speaker/Mic and a Plantronics Voyager Legend headset.

I can pair both successfully, however, they DO NOT WORK in HSP/HFP mode, I can only use them for audio output in A2DP Sync mode.

I have tested this on both the GA 4.15 kernel and the HWE 5.0 kernel with the same issue on each. HSP/HFP does not work.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.18.0-25-generic 4.18.0-25.26~18.04.1
ProcVersionSignature: Ubuntu 4.18.0-25.26~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-25-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
CurrentDesktop: Unity:Unity7:ubuntu
Date: Wed Aug 21 13:14:02 2019
InstallationDate: Installed on 2016-02-11 (1286 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160210)
SourcePackage: linux-signed-hwe
UpgradeStatus: No upgrade log present (probably fresh install)