How to define multiple audio devices in device tree sound node

Thank you Yordan for referring me to the other thread. I did posted my question there and got my concern on defining 2 separate codecs under the sound node of the device tree resolved:

solution was to do something like this:

pcm5102a: pcm5102a {
compatible = "ti,pcm5102a";
};
 
sound0:sound@0 {
compatible = "ti,pcm5102a-evm-audio";
ti,model = "TI PCM5102A";
ti,audio-codec = <&pcm5102a>;
ti,mcasp-controller = <&mcasp0>;
ti,codec-clock-rate = <24000000>;
};
 

sound1:sound@1 {
compatible = "ti,pcm3168a";
};
 
sound {
compatible = "ti,pcm3168a-evm-audio";
ti,model = "TI PCM3168A";
ti,audio-codec = <&pcm3168a>;
ti,mcasp-controller = <&mcasp1>;
ti,codec-clock-rate = <24000000>;
};
 

My new question is regarding the mcasp1 node itself and its parameters definition; what I mean, is asking if the following settings are correct for configuring the TI PCM3168a codec (this codec provides 8OUTPUT and 6 INPUTS) for my requirements:

&mcasp1 {

pinctrl-names = "default", "sleep";

pinctrl-0 = <&mcasp1_pins>;

pinctrl-1 = <&mcasp1_sleep_pins>;

status = "okay";

op-mode = <0>; /* MCASP_IIS_MODE */

tdm-slots = <10>; /* 8 slots for TX and 2 Slots for RX */

/* 16 serializer */

serial-dir = < /* 0:INACTIVE,  1:TX,    2:RX */

1 0 2 0

>;

tx-num-evt = <32>;

rx-num-evt = <32>;

};

My basic requirements for using this multichannel codec on Mcasp1 are:

- Use mcasp1 data pin AXR0 for TX and AXR2 for RX

- Setup TX for only 8 audio output channels (8 speakers)

- Setup RX for only 2 audio inputs (2 Mics)

- My audio data samples are 16bits/samples, so I will have 16*10 slots=160bits/frame (2 slots RX, 8 slots TX)

- We are using the same bit clock and frame sync clocks for RX and TX

1)  My main question is regarding the "tdm-slots = <10>;": Is this correct for handling 8 TX and 2 RX slots? How McASP will know which slots are TX and RX and sent TX streams to AXR0 while getting RX streams from AXR2?

2) Is using   "op-mode = <0>; /* MCASP_IIS_MODE */"  make sense in this use case where we are dealing with multiple channels and I2S is known to be used only for stereo (2 chan) operation?

Hi,

PEleph said:

1)  My main question is regarding the "tdm-slots = <10>;": Is this correct for handling 8 TX and 2 RX slots? How McASP will know which slots are TX and RX and sent TX streams to AXR0 while getting RX streams from AXR2?

The <serial-dir> parameter provides this information. In the settings you provide: 

PEleph said:

serial-dir = < /* 0:INACTIVE,  1:TX,    2:RX */

1 0 2 0

>;

Only 4 serializers will be used   

AXR0 as TX, AXR1 -> Inactive, AXR2 as RX, AXR3 -> Inactive

Regarding your second question, op-mode can be either 0 or 1: 

0: I2S mode, used for I2S, PCM and TDM protocols

1: DIT mode, used for S/PDIF protocol 

You need to determine which of the two is most suitable fro your use case. IMO you could use I2S mode. 

Best Regards, 
Yordan

• op-mode

  • 0: I2S mode, used for I2S, PCM and TDM protocols

  • 1: DIT mode, used for S/PDIF protocol

I found an issue with overlaying the 2 sounds nodes for the 2 different sound cards I referred to, in my Nov 30th post of this thread.

If I defined as recommended (sound0 and sound1 in separate nodes), I can successfully send data to sound0 underlying mcasp driver, but sending data to sound1 underlying driver does not get called by the underlying davinci-mcasp driver, even though the driver for sound1 got correctly loaded by the kernel and shows up when I list the audio devices with following cmd for example: "cat /proc/asound/devices."

It looks like just defining sound0 and sound1 does not really overlay the 2 codecs to be used, just the first one (sound0) takes precedence! am I missing something else for properly overlaying the 2 sound nodes?

Brad,

Yes, when ONLY one node is defined in dts (sound1 or sound0), it works; meaning, I can send and see (scope) data on the respective mcasp (mcasp0 or mcasp1) data pin. That is why I think there is issue with overlaying both nodes.

Do you have a script using devmem2 that dumps the McASP register configuration at run-time?  I think you may have made a simple one for an earlier issue we debugged.  Can you run it on McASP0 for the two cases (i.e. sound0+sound1 and sound1-only)?

Pablo,

You are confusing tdm-slots with serial-dir.  The serial-dir field is where you program the number of pins/serializers being used.  The PCM3168 has 3 output pins and 4 input pins.  The PCM3168 is transferring two channels of data per pin.  This corresponds to tdm-slots=2.  The serial-dir field is where you specify which serializers of the McASP are inputs and which are outputs.

Note, however, that McASP0 and McASP1 have 4 serializers each.  So for example if you need all 7 serializers then you would need to put the 3 McASP inputs on McASP0 and the 4 McASP outputs on McASP1.

Please start a new thread for your questions.  They are fundamentally different than the question/issue in this thread.

Brad