IMX8MP - AD1939 audio codec capture issue

Airbus_A320 — Mon, 24 Oct 2022 11:09:14 GMT

Hi,

I'm having some trouble with an AD1939 codec. I need my application to work in TDM mode (8 playback streams on a single lane and 4 capture streams on a single lane) and the CPU to be the clock master. I managed to get the codec recognized by the kernel and it playbacks OK. I'm having a hard time getting the capture streams configured.

Here is a snippet of my device tree:

/ { sound-ad193x { compatible = "simple-audio-card"; simple-audio-card,name = "ad193x-audio"; simple-audio-card,format = "dsp_a"; simple-audio-card,frame-master = <&cpudai>; simple-audio-card,bitclock-master = <&cpudai>; simple-audio-card,mclk-fs = <256>; cpudai: simple-audio-card,cpu { sound-dai = <&sai2>; dai-tdm-slot-num = <8>; dai-tdm-slot-width = <32>; }; codecdai:simple-audio-card,codec { sound-dai = <&codec_audio_analog>; }; }; }; &ecspi2 { codec_audio_analog: ad1939_spi@0 { compatible = "ad1939"; reg = <0>; spi-max-frequency = <1000000>; #sound-dai-cells = <0>; status = "okay"; }; }; &sai2 { #sound-dai-cells = <0>; pinctrl-names = "default"; pinctrl-0 = <&pinctrl_sai2>; assigned-clocks = <&clk IMX8MP_CLK_SAI2>; assigned-clock-parents = <&clk IMX8MP_AUDIO_PLL1_OUT>; assigned-clock-rates = <12288000>; clocks = <&audio_blk_ctrl IMX8MP_CLK_AUDIO_BLK_CTRL_SAI2_IPG>, <&clk IMX8MP_CLK_DUMMY>, <&audio_blk_ctrl IMX8MP_CLK_AUDIO_BLK_CTRL_SAI2_MCLK1>, <&clk IMX8MP_CLK_DUMMY>, <&clk IMX8MP_CLK_DUMMY>; clock-names = "bus", "mclk0", "mclk1", "mclk2", "mclk3"; fsl,dataline = <0 0x1 0x1>; fsl,sai-mclk-direction-output; status = "okay"; }; &iomuxc { pinctrl_sai2: sai2grp { fsl,pins = < MX8MP_IOMUXC_SAI2_TXC__AUDIOMIX_SAI2_TX_BCLK 0x000000D6 MX8MP_IOMUXC_SAI2_TXD0__AUDIOMIX_SAI2_TX_DATA00 0x00000196 MX8MP_IOMUXC_SAI2_TXFS__AUDIOMIX_SAI2_TX_SYNC 0x000000D6 MX8MP_IOMUXC_SAI2_RXD0__AUDIOMIX_SAI2_RX_DATA00 0x000000D6 >; }; };

The configuration sent by the codec driver over the SPI bus looks fine to me. Here is a screenshot of the signals I get:

When I try to record I get just noise. Reproducing the wave file through my logic analyzer looks like the whole 8-slot frame gets "compressed" into 4 frames (muting first channel one and then channel two while recording I see during playback that the most significant bit of channel one got zeroed first then the least significant ones). Another symptom is that if I lunch arecord with a duration flag it records for exactly twice the time!

~# time arecord -fs16 -r48000 -c4 /dev/null --duration 2 Recording WAVE '/dev/null' : Signed 16 bit Little Endian, Rate 48000 Hz, Channels 4 real 0m4.136s user 0m0.056s sys 0m0.024s

My theory is the bit clock inside the receiver got somehow halved...
Peeking at the sai registers during the recording I see MSEL in RCR2 is 00, I was expecting it to be 01 as in TCR2.

If I configure the codec to be the clock master all works as expected.

Can anybody please help me?
Thanks

Re: IMX8MP - AD1939 audio codec capture issue

Airbus_A320 — Wed, 26 Oct 2022 09:13:54 GMT

Answering myself in case somebody needs a hint on a similar issue.

The problem was I had clocked the SAI peripheral at the same rate my bit clock is. I have 8 32-bit slots at 48 kHz, so my bit clock is 12.288 MHz and in my device tree I had assigned-clock-rates = <12288000>

Running out of ideas I tried to reduce the slot count to 4 (bit clock 6.144 MHz) and all went fine. So I tried to revert to 8 slots and increase assigned-clock-rates to twice the bit clock. Now I can playback and capture w/o any issue.

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IMX8MP - AD1939 audio codec capture issue

Re: IMX8MP - AD1939 audio codec capture issue