topic Re: Using MIPI MCLK for audio codec clock in i.MX Processors

Using MIPI MCLK for audio codec clock

jsmith8831 — Mon, 19 Feb 2024 18:05:27 GMT

Hello,

We have a custom i.MX8QM board, and the MCLK input pin on the PCM3168A audio codec is routed to the MIPI_CSI0_MCLK_OUT pin on the iMX8QM.

I have tried adding &csi0_core_lpcg to the clocks section in the device tree instead of &mclkout0_lpcg, but I'm getting errors when try to play an audio file.

How do I enable the MIPI MCLK and set the frequency so that the audio codec can function?

// I2C pcm3168a: audio-codec@44 { compatible = "ti,pcm3168a"; reg = <0x44>; reset-gpios = <&lsio_gpio4 24 GPIO_ACTIVE_LOW>; clocks = <&csi0_core_lpcg 0>; clock-names = "scki"; assigned-clocks = <&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_PLL>, <&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_SLV_BUS>, <&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_MST_BUS>, <&csi0_core_lpcg 0>; assigned-clock-rates = <36864000>, <24576000>, <12288000>, <12288000>; #sound-dai-cells = <0>; VDD1-supply = <&reg_3v3>; VDD2-supply = <&reg_3v3>; VCCAD1-supply = <&reg_5v0>; VCCAD2-supply = <&reg_5v0>; VCCDA1-supply = <&reg_5v0>; VCCDA2-supply = <&reg_5v0>; pinctrl-names = "default"; pinctrl-0 = <&pinctrl_audio_reset &pinctrl_codec_clk>; }; // IOMUX pinctrl_codec_clk: codec_clk { fsl,pins = < IMX8QM_MIPI_CSI0_MCLK_OUT_MIPI_CSI0_ACM_MCLK_OUT 0xc0000020 >; };

# aplay some_audio.wav [ 59.878902] pcm3168a 4-0044: unsupported sysclk ratio [ 59.884023] pcm3168a 4-0044: ASoC: error at snd_soc_dai_hw_params on pcm3168a-dac: -22 [ 59.892294] 59040000.sai-pcm3168a-dac: ASoC: soc_pcm_hw_params() failed (-22) ALSA lib ../../../alsa-lib-1.2.6.1/src/pcm/pcm_direct.c:1305:(snd1_pcm_direct_initialize_slave) unable to install hw params ALSA lib ../../../alsa-lib-1.2.6.1/src/pcm/pcm_dmix.c:1013:(snd_pcm_dmix_open) unable to initialize slave aplay: main:831: audio open error: Invalid argument

Re: Using MIPI MCLK for audio codec clock

jimmychan — Thu, 22 Feb 2024 02:36:32 GMT

MIPI_CSI0_MCLK_OUT is for camera used, not for audio codec.

Re: Using MIPI MCLK for audio codec clock

jsmith8831 — Thu, 22 Feb 2024 02:46:25 GMT

Hi @jimmychan ,

Thank you for the response. Yes, I am aware that this pin is meant for a camera, but it was an oversight by our hardware team. According to the PCM3168A datasheet, any clock will do and it can be an external clock. So basically, I would like to re-purpose the MIPI MCLK pin as a clock with a specific frequency. I searched for examples on how to do this, but so far I have not found any. Is there a way to do this?

Re: Using MIPI MCLK for audio codec clock

jsmith8831 — Thu, 04 Apr 2024 14:12:54 GMT

I ended up resolving this by adding an external clock for now. My device tree now looks like this:

codec_osc: fixed-22579200 { compatible = "fixed-clock"; #clock-cells = <0>; clock-frequency = <22579200>; clock-accuracy = <20000>; }; sound_card: sound-card { compatible = "simple-audio-card"; simple-audio-card,name = "PCM3168A"; simple-audio-card,widgets = "Speaker", "Channel1out", "Speaker", "Channel2out", "Speaker", "Channel3out", "Speaker", "Channel4out", "Speaker", "Channel5out", "Speaker", "Channel6out", "Speaker", "Channel7out", "Speaker", "Channel8out", "Microphone", "Channel1in", "Microphone", "Channel2in", "Line", "Channel3in", "Line", "Channel4in"; simple-audio-card,routing = "Channel1out", "AOUT1L", "Channel2out", "AOUT1R", "Channel3out", "AOUT2L", "Channel4out", "AOUT2R", "Channel5out", "AOUT3L", "Channel6out", "AOUT3R", "Channel7out", "AOUT4L", "Channel8out", "AOUT4R", "AIN1L", "Channel1in", "AIN1R", "Channel2in", "AIN2L", "Channel3in", "AIN2R", "Channel4in"; simple-audio-card,dai-link@0 { format = "left_j"; bitclock-master = <&pcm3168_dac>; frame-master = <&pcm3168_dac>; mclk-fs = <512>; cpu { sound-dai = <&sai0>; dai-tdm-slot-num = <8>; dai-tdm-slot-width = <32>; }; pcm3168_dac: codec { sound-dai = <&pcm3168a 0>; clocks = <&codec_osc>; dai-tdm-slot-num = <8>; dai-tdm-slot-width = <32>; }; }; simple-audio-card,dai-link@1 { format = "left_j"; bitclock-master = <&pcm3168_adc>; frame-master = <&pcm3168_adc>; cpu { sound-dai = <&sai0>; dai-tdm-slot-num = <8>; dai-tdm-slot-width = <32>; }; pcm3168_adc: codec { sound-dai = <&pcm3168a 1>; clocks = <&codec_osc>; dai-tdm-slot-num = <8>; dai-tdm-slot-width = <32>; }; }; }; pcm3168a: audio-codec@44 { compatible = "ti,pcm3168a"; reg = <0x44>; reset-gpios = <&lsio_gpio4 24 GPIO_ACTIVE_LOW>; clocks = <&codec_osc>; clock-names = "scki"; clock-frequency = <22579200>; #sound-dai-cells = <1>; VDD1-supply = <&reg_3v3>; VDD2-supply = <&reg_3v3>; VCCAD1-supply = <&reg_5v0>; VCCAD2-supply = <&reg_5v0>; VCCDA1-supply = <&reg_5v0>; VCCDA2-supply = <&reg_5v0>; pinctrl-names = "default"; pinctrl-0 = <&pinctrl_audio_reset>; };