ASoC: No stereo on Banana Pi M2 headphone jack

Hi all,

I'm in need for stereo sound on the headphone jack of a Banana Pi M2 (Allwinner A31s), but I'm getting only mono differential (I assume at least, because I can hear both channels in either speaker).

In alsamixer, there is a switch to select between stereo and mono diffential output for the LINE output (that has no notable effect), but not for the Headphone output.

Driver limitation/bug? Hardware deficiency? Configuration error? Any other idea?

FWIW, this is the DT overlay to get any sound at all:

/dts-v1/;
/plugin/;

/ {
	fragment@0 {
		target = <&codec>;
		__overlay__ {
			status = "okay";
			allwinner,audio-routing = "Headphone", "HP";
		};
	};
};

Regards,
Michael

Never mind; This happens if you plug a CTIA headset into a OMTP jack.

Michael