IMX8MP PDM Microphone SPH0641LM4H-1

[jgsandom]

Hi all, we're trying to integrate the SPH0641LM4H-1 PDM microphone and we're having a few issues, we're trying to use this command to test the output;

arecord -f S32_LE -d 10 -r 48000 --device="hw:0,0" -vvv

Seem to just get a continuous stream which is saturated at 99% e.g.;

arecord -f S32_LE -d 10 -r 48000 --device="hw:0,0" -vvv
Recording WAVE 'stdin' : Signed 32 bit Little Endian, Rate 48000 Hz, Mono
Hardware PCM card 0 'imx-audio-micfil' device 0 subdevice 0
Its setup is:
  stream       : CAPTURE
  access       : RW_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 1
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 16384
  period_size  : 4096
  period_time  : 85333
  tstamp_mode  : NONE
  tstamp_type  : MONOTONIC
  period_step  : 1
  avail_min    : 4096
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 16384
  silence_threshold: 0
  silence_size : 0
  boundary     : 4611686018427387904
  appl_ptr     : 0
  hw_ptr       : 0
RIFF$LWAVEfmt ��� dataLMax peak (4096 samples): 0x7fffe500 #################### 99%
���������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������Max peak (4096 samples): 0x7fffe000 #################### 99%

The kernel log looks fine, don't see any issues there;

dmesg -wH | grep mic
[  +0.006196] DMA: preallocated 256 KiB pool for atomic allocations
[  +0.011044] fsl-micfil-dai 30ca0000.micfil: GET IRQ: 39
[  +0.005251] fsl-micfil-dai 30ca0000.micfil: GET IRQ: 40
[  +0.005243] fsl-micfil-dai 30ca0000.micfil: GET IRQ: 41
[  +0.005245] fsl-micfil-dai 30ca0000.micfil: GET IRQ: 42
[  +0.008303] debugfs: Directory '30ca0000.micfil' with parent 'imx-audio-micfil' already present!
[  +0.008880] imx-micfil sound-micfil: snd-soc-dummy-dai <-> 30ca0000.micfil mapping ok
[  +0.007843] imx-micfil sound-micfil: ASoC: no DMI vendor name!
[  +0.002977]   #0: imx-audio-micfil

The dts entry looks like this;

sound-micfil {
	compatible = "fsl,imx-audio-micfil";
	model = "imx-audio-micfil";
	cpu-dai = <&micfil>;
};

&micfil {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_pdm>;
	assigned-clocks = <&clk IMX8MP_CLK_PDM>;
	assigned-clock-parents = <&clk IMX8MP_AUDIO_PLL1_OUT>;
	assigned-clock-rates = <196608000>;
	status = "okay";
};

pinctrl_pdm: pdmgrp {
	fsl,pins = <
		MX8MP_IOMUXC_SAI5_RXC__AUDIOMIX_PDM_CLK			0xd6
		MX8MP_IOMUXC_SAI5_RXD0__AUDIOMIX_PDM_BIT_STREAM00	0xd6
		MX8MP_IOMUXC_SAI5_RXD1__AUDIOMIX_PDM_BIT_STREAM01	0xd6
		MX8MP_IOMUXC_SAI5_RXD2__AUDIOMIX_PDM_BIT_STREAM02	0xd6
		MX8MP_IOMUXC_SAI5_RXD3__AUDIOMIX_PDM_BIT_STREAM03	0xd6
	>;
};

Does anyone have any idea what could be the issue? note that we haven't had the chance to scope the PDM clock and data lines yet, so can't completely discount an electronics issue. (will be doing this next week).

I've also seen that there is a sound-swpdm node, should this be used instead of sound-micfil? Some clarification would be appreciated!

Thank you

[jgsandom · Accepted solution]

@igorpadykov I tried both options and they didn't work unfortunately for RX2. I made some additional modifications as suggested in my previous post. It works ok for me - I've attached the patch.

[igorpadykov]

Hi Joe

for pdm testing one can look at sect.7.6 PDM Microphone Interface (MICFIL)

i.MX Linux Reference Manual​

unit test

https://source.codeaurora.org/external/imx/imx-test/tree/test/mxc_pdm_test?h=lf-5.10.y_2.0.0

I.MX 8Mic Board Quick Start Guide, sect.3 Record Audio
https://www.nxp.com/docs/en/quick-reference-guide/IMX-8MIC-QSG.pdf

dts file:

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm64/boot/dts/freescale/imx8mp-evk.d...

Best regards
igor