Understanding audio routing in linux for wm8985

[jamalmohiuddin]

I have a custom i.MX6 board which has WM8985 audio codec. I have the codec driver wm8985 in sound/soc/codecs folder. I am developing the machine level driver sound/soc/fsl/imx-wm8985.c

I am taking the wm8962 code as reference. I am unable to understand the audio routing concept in linux audio subsystem.

I have modified the device tree to the following looking at wm8962 device tree.

sound {                 compatible = "fsl,imx6q-sabresd-wm8985",                            "fsl,imx-audio-wm8985";                 model = "wm8985-audio";                 cpu-dai = <&ssi2>;                 audio-codec = <&codec>;                 audio-routing =                         "Headphone Jack", "HPL",                         "Headphone Jack", "HPR",                         "Ext Spk", "SPKL",                         "Ext Spk", "SPKR",                         "Mic Bias", "AMIC",                         "RIN", "Mic Bias",                         "DMIC", "Mic Bias",                         "DMICDAT", "DMIC";                 mux-int-port = <2>;                 mux-ext-port = <3>;                 hp-det-gpios = <&gpio7 8 1>; /* same as sabre */                 /*mic-det-gpios = <&gpio1 23 1>;*/ /* move to enet_ref_clk */         };

Is this correct. Can you please help me to understanding what does the source and sink means in this. How to make a route..

Running aplay, i am getting Read/Write Error which happens due to incorrect routing..

[igorpadykov]

Hi Jamal

for source and sink routing one can refer to documentation in

linux/Documentation/devicetree/bindings/sound/imx-audio-wm8962.txt

linux-imx.git - i.MX Linux Kernel 

and Chapter 7 Audio attached Linux Manual, alsa project online documentation

ALSA Driver Documentation - AlsaProject 
https://www.alsa-project.org/main/index.php/Tutorials_and_Presentations 

Best regards
igor
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[jamalmohiuddin]

I was able to write the driver. But when i am trying to play the audio it is failing : pcm write I/O Error . How to debug

[igorpadykov]

please use driver sources in Linux Manual and AN4553 Using Open Source

Debugging Tools for Linux on i.MX Processors
https://www.nxp.com/docs/en/application-note/AN4553.pdf

for testing hardware may be useful baremetal sdk:

Github SDK
https://github.com/backenklee/swp-report/tree/master/iMX6_Platform_SDK

Best regards
igor