Codec WM8904 is connected to imx via i2s and i2c, i2s (SAI3) connection is as follows:
MCLK pin on codec has 12.288Mhz oscillator.
How do I configure device tree for SAI3 to work in slave mode?
These are the default parameters in device tree:
sai3: sai@30030000 {
#sound-dai-cells = <0>;
compatible = "fsl,imx8mm-sai", "fsl,imx8mq-sai";
reg = <0x30030000 0x10000>;
interrupts = <GIC_SPI 50 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clk IMX8MM_CLK_SAI3_IPG>, <&clk IMX8MM_CLK_DUMMY>,
<&clk IMX8MM_CLK_SAI3_ROOT>,
<&clk IMX8MM_CLK_DUMMY>, <&clk IMX8MM_CLK_DUMMY>;
clock-names = "bus", "mclk0", "mclk1", "mclk2", "mclk3";
dmas = <&sdma2 4 2 0>, <&sdma2 5 2 0>;
dma-names = "rx", "tx";
status = "disabled";
};
&sai3 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai3>;
assigned-clocks = <&clk IMX8MM_CLK_SAI3>;
assigned-clock-parents = <&clk IMX8MM_AUDIO_PLL1_OUT>;
assigned-clock-rates = <24576000>;
status = "disabled";
};
pinctrl_sai3: sai3grp {
fsl,pins = <
MX8MM_IOMUXC_SAI3_TXFS_SAI3_TX_SYNC 0xd6
MX8MM_IOMUXC_SAI3_TXC_SAI3_TX_BCLK 0xd6
MX8MM_IOMUXC_SAI3_TXD_SAI3_TX_DATA0 0xd6
MX8MM_IOMUXC_SAI3_RXD_SAI3_RX_DATA0 0xd6
>;
};
Relevant codec entries:
sound {
compatible = "fsl,imx-audio-wm8904";
model = "imx-wm8904";
sai-controllers = <&sai3 &sai3>;
cpu-dai = <&sai3>;
audio-codec = <&wm8904>;
codec-master;
audio-routing =
"Headphone Jack", "HPOUTR",
"Headphone Jack", "HPOUTL",
"IN2L", "Line In Jack",
"IN2R", "Line In Jack",
"Mic Jack", "MICBIAS",
"IN1L", "Mic Jack",
"IN1R", "Mic Jack";
};
&i2c2 {
clock-frequency = <400000>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_i2c2>;
status = "okay";
wm8904: wm8904@1a {
compatible = "wlf,wm8904";
reg = <0x1a>;
clocks = <&clk IMX8MM_CLK_SAI3_ROOT>;
clock-names = "mclk";
};
};
This seems to work, I can record sound from microphone, however there are issues. Right channel on codec has periodic clicking sounds, and occasionally left and right channel get swapped during long recording. I measured BCLK line on scope, and it shows 1.536Mhz, which corresponds to default register settings in WM8904. WM8904 has SYSCLK = MCLK/2 = 6.144Mhz
BCLK = SYSCLK/4 = 1.536Mhz
I feel like I can just delete most entries under SAI3 since they're written for the case when SAI3 is master on imx side, right? I don't need any values for "assigned clock rates" under &SAI3 node, since BCLK is received from WM8904.
In this thread, guy from NXP said that TXC stays the same both for master/slave mode on imx side. So my i2s connection is correct, right?
I did notice that when I use a level shifter to 3.3V for the i2c2 that the codec uses between itself and CPU, the clicks go away. So my question is: why would direct 1.8V &i2c2 (which is i2c1 actually) connection between codec and CPU (without level shifter) cause clicks on the recorded audio file into an internal emmc memory, if something concurrently is being written onto external SD card (USDHC2 interface).
