If we want to use the microphone function of the wm8978 codec,
we must enable the microphone bias circuit and power up the bias
circuit,otherwise the microphone can not vibrate for sound source
sampling.The bit that controls the output voltage of the bias circuit
is the fourth bit of the WM8978_POWER_MANAGEMENT_1 register,so this
bit must be set to 1.This patch can support the recording function of
the wm8978 codec.

Signed-off-by: Mengchen Li <mengchenli64@gmail.com>
---
 sound/soc/codecs/wm8978.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/wm8978.c b/sound/soc/codecs/wm8978.c
index a682f80..fdd5429 100644
--- a/sound/soc/codecs/wm8978.c
+++ b/sound/soc/codecs/wm8978.c
@@ -822,7 +822,9 @@ static int wm8978_hw_params(struct snd_pcm_substream *substream,
 
 	snd_soc_component_write(component, WM8978_AUDIO_INTERFACE, iface_ctl);
 	snd_soc_component_write(component, WM8978_ADDITIONAL_CONTROL, add_ctl);
-
+	/* Enable MICBEN */
+	snd_soc_component_write(component, WM8978_POWER_MANAGEMENT_1,
+		snd_soc_component_read(component, WM8978_POWER_MANAGEMENT_1) | 0x10);
 	if (wm8978->sysclk != current_clk_id) {
 		if (wm8978->sysclk == WM8978_PLL)
 			/* Run CODEC from PLL instead of MCLK */
-- 
2.7.4

On Mon, Sep 12, 2022 at 04:23:05PM +0800, Mengchen Li wrote:

> @@ -822,7 +822,9 @@ static int wm8978_hw_params(struct snd_pcm_substream *substream,
>  
>  	snd_soc_component_write(component, WM8978_AUDIO_INTERFACE, iface_ctl);
>  	snd_soc_component_write(component, WM8978_ADDITIONAL_CONTROL, add_ctl);
> -
> +	/* Enable MICBEN */
> +	snd_soc_component_write(component, WM8978_POWER_MANAGEMENT_1,
> +		snd_soc_component_read(component, WM8978_POWER_MANAGEMENT_1) | 0x10);

This should be done by creating a supply widget for the MICBIAS
which will be connected by the machine driver to the microphone
widget.  This will mean that the MICBIAS is only enabled when
it's actively being used which saves power.  Look for MICBIAS
widgets in other CODEC drivers for examples.