There is no Digital Microphone clock on DragonBoard 410c board

Hello,
 I'm testing one Digital microphone on DragonBoard 410c board(BSP:Debian 17.04 or 19.01) accroding to below document:


But I can’t get clock(it’s 1.275MHz on STM32F401 Nucleo-64 board) from UART0-TX in the test.
Does anybody have some suggestions? Thank you very much.

I changed the file msm8916-wcd-digital.c as below:
diff --git a/sound/soc/codecs/msm8916-wcd-digital.c b/sound/soc/codecs/msm8916-wcd-digital.c
snd_soc_update_bits(codec, LPASS_CDC_CLK_DMIC_B1_CTL,
DMIC_B1_CTL_DMIC0_CLK_SEL_MASK,

  • DMIC_B1_CTL_DMIC0_CLK_SEL_DIV3);
    
  • DMIC_B1_CTL_DMIC0_CLK_SEL_DIV16);
    

    switch (dmic) {
    case 1:

    snd_soc_update_bits(codec, LPASS_CDC_TX1_DMIC_CTL,
    TXN_DMIC_CTL_CLK_SEL_MASK,

  • TXN_DMIC_CTL_CLK_SEL_DIV3);
  • TXN_DMIC_CTL_CLK_SEL_DIV16);
    break;
    case 2:

snd_soc_update_bits(codec, LPASS_CDC_TX2_DMIC_CTL,
TXN_DMIC_CTL_CLK_SEL_MASK,

  • TXN_DMIC_CTL_CLK_SEL_DIV3);
  • TXN_DMIC_CTL_CLK_SEL_DIV16);

I got DMIC_CLK(1.19MHZ) and MIC_BIAS(2.7V) after below commands performed:
$amixer -c 0 cset iface=MIXER,name=‘DEC1 MUX’ ‘DMIC1’
$arecord -D plughw:0,2 -r 48000 -f S16_LE /tmp/f-48000.wav

But there’s no voice when we play f-48000.wav that we recorded.