You need to configure alsamixer to open the microphone path, try the following settings:
<path name="media-headset-mic">
<ctl name="MIC2 SRC" value="MIC2"/>
<ctl name="LADC input Mixer MIC2 boost Switch" value="1"/>
<ctl name="RADC input Mixer MIC2 boost Switch" value="1"/>
<ctl name="ADCL Mux" value="ADC"/>
<ctl name="ADCR Mux" value="ADC"/>
<ctl name="AIF1 AD0L Mixer ADCL Switch" value="1"/>
<ctl name="AIF1 AD0R Mixer ADCR Switch" value="1"/>
<ctl name="AIF1OUT0L Mux" value="AIF1_AD0L"/>
<ctl name="AIF1OUT0R Mux" value="AIF1_AD0R"/>
<ctl name="ADC volume" value="160"/>
</path>
That seems to be how Android configures the MIC2
Edit: it's MIC2, not MIC1...
<path name="media-headset-mic">
<ctl name="MIC2 SRC" value="MIC2"/>
<ctl name="LADC input Mixer MIC2 boost Switch" value="1"/>
<ctl name="RADC input Mixer MIC2 boost Switch" value="1"/>
<ctl name="ADCL Mux" value="ADC"/>
<ctl name="ADCR Mux" value="ADC"/>
<ctl name="AIF1 AD0L Mixer ADCL Switch" value="1"/>
<ctl name="AIF1 AD0R Mixer ADCR Switch" value="1"/>
<ctl name="AIF1OUT0L Mux" value="AIF1_AD0L"/>
<ctl name="AIF1OUT0R Mux" value="AIF1_AD0R"/>
<ctl name="ADC volume" value="160"/>
</path>
That seems to be how Android configures the MIC2
Edit: it's MIC2, not MIC1...
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