DMIC-DFSDM Interface on OSD32MP1-RED board

[Farid Azhar]

We are trying to interface a single Digital Microphone with PDM output to OSD32MP1-RED board using DFSDM peripheral.
I’ve modifed the devicetree (kernel, uboot, tfa) for the following signals between DMIC and RPi connector (JP20) on OSD32MP1-RED board.

DMIC_DATA => JP20/p.10 => PB12 (DFSDM1_DATIN1)
DMIC_GND => JP20/p.6
DMIC_CLK => JP20/p.36 => PB13 (DFSDM1_CKOUT)
DMIC_VDD => JP20/p.1 (3.3V)

Code compiles and runs OK, and I see the dfsdm iio node and alsa command “arecord -l” shows the soundcard entry.
$ sudo arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: STM32MP1DK [STM32MP1-DK], device 0: 4400d000.dfsdm:filter@0:dfsdm-d-dmic-hifi dmic-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
$

The audio record command completes successfully but the captured audio file is empty, no sound at all.
After some debugging I found that DFSDM Clock on pin PB13 (DFSDM1_CKOUT) is not generating when recording is started, tested with the oscilloscope.
It looks the DFSDM driver is not generating the clock or got the wrong clock setting.

I followed the application note AN5027, DFSDM Devicetree structure in STM32MP157C-EV1 board and the STM32CubeMX.
Following are the changes I made in OSD32MP1-RED board device tree. Would appreciate if someone could point out if something is wrong or missing here.

Updates in kernel DT file “osd32mp1-red.dts”
——————————————-
sound {
compatible = “audio-graph-card”;
label = “STM32MP1-DK”;
dais = <&dfsdm0_port>;
status = “okay”;
};

dmic0: dmic-0 {
compatible = “dmic-codec”;
sound-name-prefix = “dmic0”;
#sound-dai-cells = <1>;
status = “okay”;

port {
dmic0_endpoint: endpoint {
remote-endpoint = <&dfsdm_endpoint0>;
};
};
};

&dfsdm {
pinctrl-names = “default”, “sleep”;
pinctrl-0 = <&dfsdm_pins_mx>;
pinctrl-1 = <&dfsdm_sleep_pins_mx>;
status = “okay”;

/* USER CODE BEGIN dfsdm */
spi-max-frequency = <30000000>;
clocks = <&rcc DFSDM_K>, <&rcc ADFSDM_K>;
clock-names = “dfsdm”, “audio”;

dfsdm0: filter@0 {
compatible = “st,stm32-dfsdm-dmic”;
st,adc-channels = <1>;
st,adc-channel-names = “dmic0”;
st,adc-channel-types = “SPI_R”;
st,adc-channel-clk-src = “CLKOUT”;
st,filter-order = <3>;
status = “okay”;

asoc_pdm0: dfsdm-dai {
compatible = “st,stm32h7-dfsdm-dai”;
#sound-dai-cells = <0>;
io-channels = <&dfsdm0 0>;
status = “okay”;

dfsdm0_port: port {
dfsdm_endpoint0: endpoint {
remote-endpoint = <&dmic0_endpoint>;
};
};
};
};
/* USER CODE END dfsdm */
};

&pinctrl {
u-boot,dm-pre-reloc;

dfsdm_pins_mx: dfsdm_mx-0 {
pins1 {
pinmux = <STM32_PINMUX(‘B’, 12, AF6)>; /* DFSDM1_DATIN1 */
bias-disable;
};
pins2 {
pinmux = <STM32_PINMUX(‘B’, 13, AF3)>; /* DFSDM1_CKOUT */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
};

dfsdm_sleep_pins_mx: dfsdm_sleep_mx-0 {
pins {
pinmux = <STM32_PINMUX(‘B’, 12, ANALOG)>, /* DFSDM1_DATIN1 */
<STM32_PINMUX(‘B’, 13, ANALOG)>; /* DFSDM1_CKOUT */
};
};

Updates in u-boot DT file “osd32mp1-red-u-boot.dtsi”
——————————————-
CLK_SAI1_PLL4Q
CLK_SAI2_DISABLED
CLK_SAI3_DISABLED
CLK_SAI4_DISABLED

Updates in tfa DT file “osd32mp1-red.dts”
——————————————-
CLK_SAI1_PLL4Q
CLK_SAI2_DISABLED
CLK_SAI3_DISABLED
CLK_SAI4_DISABLED
DECPROT(STM32MP1_ETZPC_DFSDM_ID, DECPROT_NS_RW, DECPROT_UNLOCK)
DECPROT(STM32MP1_ETZPC_SAI1_ID, DECPROT_NS_RW, DECPROT_UNLOCK)

[Neeraj Dantu]

Issue was resolved offline.

spi-max-frequency was set tp 30MHz causing an error in DFSDM interface setup. sps-max-frequency should be 3MHz.

Neeraj

[Author]

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