Dear Nimish,
Please check the feature table from web document site.
And the PDF file of feature table:
Currently MediaTek don’t support HFP for Yocto.
HFP requires an additional 4 PCM pins, but the Azurewave 7921 module (2 antennas) does not expose the PCM/SCO pins, resulting in the HFP function being unusable.
If you could make your own board, you’ll need to do some rework to the MT7921 module. I’m not sure if the EVK has these pins on M.2 connector. You’ll need to check the schematics yourself.
However, currently we don’t support COB 7921 module or 3 Antenna MT7921 modules with Yocto OS.
Please note that 3 Antenna MT7921 modules supports Android OS only, both the firmware and driver are not compatible with Linux upstream and Yocto.
You could try HFP by ACL (voip) instead of HFP by SCO (PCM/modem call). But MediaTek hasn’t verified HFP by ACL yet.