Audio
This chapter is designed to assist developers in the progress of porting audio drivers and software to the EVK.
Integrating an External Audio Codec
In some cases, customer may want to intergrate an external audio codec to the platform. Here will introduce the DAI driver and DAI link, and explain what needs to be done to intergrate an external audio codec.
This diagram below describes the relationship between the platform device and the codec device.
DAI driver is a software component that manages the audio interface and hardware. This driver is responsible for handling the data transfer between the audio processing units and the physical audio interface ports. The DAI driver reads the hardware description from the device tree, this includes information about the hardware interface, clock sources, pin multiplexing, and other platform specific settings.
The DAI link abstracts the relationship between the audio interfaces on the platform side and the audio codec side. It specifies how the two components should interact, including data path, clock information, sample rate, number of channels, and format settings. When an audio stream is initiated, the ALSA framework uses the DAI link configuration to set up the audio path between the platform and codec. The DAI link ensures that both sides are synchronized in terms so that audio data is transmitted without errors and distortion.
The DAI link is defined within the sound card node of the device tree. Here is an example of the DAI
link for DL_SRC_BE
on Genio 1200-EVK. From codec-0
, you can determine that the codec connected to
the DL_SRC
DAI link is PMIC.
&sound {
compatible = "mediatek,mt8395-evk";
model = "mt8395-evk";
pinctrl-names = "default";
pinctrl-0 = <&aud_pins_default>;
status = "okay";
dai-link-0 {
sound-dai = <&afe>;
dai-link-name = "DL_SRC_BE";
codec-0 {
sound-dai = <&pmic 0>;
};
};
For more details about the DAI link, please refer to the mediatek,mt8395-evk.yaml.
The codec connected by the DAI link may not always be hardware, it could also be software. Let take
dai-link-5
in the DTS file as an example, the codec connected to DMIC_BE
is dmic_codec
.
If you take the time to see what dmic_codec
is about, you will find that this node is established
in mt8195.dtsi
It linked to the code dmic.c
that actually adds a dealy before dmic starts, aiming to prevent performance issues due to hardware not
being set up yet.
dai-link-5 {
sound-dai = <&afe>;
dai-link-name = "DMIC_BE";
codec-0 {
sound-dai = <&dmic_codec>;
};
};
The actual structure for the DAI link is established within the machine driver.
static struct snd_soc_dai_link mt8195_mt6359_dai_links[] = {
...
[DAI_LINK_DL_SRC_BE] = {
.name = "DL_SRC_BE",
.no_pcm = 1,
.dpcm_playback = 1,
SND_SOC_DAILINK_REG(DL_SRC_BE),
},
For more DAI link instances, you can refer to the machine driver: mt8395-evk.c.
To summarize the above content, if you want to integrate an audio codec on the platform, please ensure that the following steps are completed.
Add a DTS file for the audio codec
Establish a DAI link in the
&sound
node in the DTS fileConnect the DAI link to the backend DAI driver
Connect the DAI link to the your codec driver
After completing these steps, your platform should be able to recognize and use the external audio codec for audio processing tasks.
Audio Interfaces
The following table will show the interfaces present on the SoC MT8370/MT8390.
Audio Interfaces |
Mode |
Master/Slave |
Sample Rate (kHz) |
Channel Count |
Maximum Bit Resolution |
Dai-Link Name |
---|---|---|---|---|---|---|
I2SO1 |
I2S |
Master |
8 ~ 192 |
2 |
32 |
ETDM1_OUT_BE |
I2SO1 |
TDM |
Master |
8 ~ 48 |
16 |
32 |
ETDM1_OUT_BE |
I2SO2 |
I2S |
Master/Slave |
8 ~ 192 |
8 |
32 |
ETDM2_OUT_BE |
I2SO2 |
TDM |
Master/Slave |
48 |
16 |
32 |
ETDM2_OUT_BE |
TDM IN |
I2S |
Master/Slave |
8 ~ 192 |
2 |
32 |
ETDM1_IN_BE |
TDM IN |
TDM |
Master/Slave |
48 |
16 |
32 |
ETDM1_IN_BE |
I2S IN |
I2S |
Master/Slave |
8 ~ 192 |
8 |
32 |
ETDM2_IN_BE |
I2S IN |
TDM |
Master/Slave |
8 ~ 48 |
16 |
32 |
ETDM2_IN_BE |
I2S IN |
TDM (Direct Path) |
Master/Slave |
8 ~ 48 |
16 |
32 |
ETDM2_IN_BE |
PMIC DL |
8 ~ 192 |
2 |
24 |
ADDA_BE |
||
PMIC UL |
8 ~ 192 |
2 |
24 |
ADDA_BE |
||
PDM1 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM2 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM3 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM4 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PCM (with SRC) |
Master/Slave |
8, 16, 32, 44.1, 48 |
2 |
24 |
PCM1_BE |
|
SPDIF OUT |
Master |
32, 44.1, 48, 88.2, 96, 192 |
2 |
24 |
||
SPDIF IN |
Slave |
32, 44.1, 48, 88.2, 96, 176.4, 192 |
2 |
24 |
||
AUDIO IN |
Slave |
8 ~ 192 |
8 |
24 |
||
HDMITX |
Master |
8 ~ 192 |
8 |
32 |
ETDM3_OUT_BE |
|
DPTX |
Master |
8 ~ 192 |
8 |
24 |
DPTX_BE |
The following table will show the interfaces present on the SoC MT8395.
Audio Interfaces |
Mode |
Master/Slave |
Sample Rate (kHz) |
Channel Count |
Maximum Bit Resolution |
Dai-Link Name |
---|---|---|---|---|---|---|
I2SO1 |
I2S |
Master |
8 ~ 384 |
2 |
32 |
ETDM1_OUT_BE |
I2SO1 |
TDM |
Master |
8 ~ 48 |
16 |
32 |
ETDM1_OUT_BE |
I2SO2 |
I2S |
Master/Slave |
8 ~ 384 |
8 |
32 |
ETDM2_OUT_BE |
I2SO2 |
TDM |
Master/Slave |
16 |
16 |
32 |
ETDM2_OUT_BE |
I2SO2 |
TDM |
Master/Slave |
48 |
16 |
32 |
ETDM2_OUT_BE |
TDM IN |
I2S |
Master/Slave |
8 ~ 384 |
2 |
32 |
ETDM1_IN_BE |
TDM IN |
TDM |
Master/Slave |
16 |
16 |
32 |
ETDM1_IN_BE |
TDM IN |
TDM |
Master/Slave |
48 |
16 |
32 |
ETDM1_IN_BE |
I2S IN |
I2S |
Master/Slave |
8 ~ 384 |
8 |
32 |
ETDM2_IN_BE |
I2S IN |
TDM |
Master/Slave |
8 ~ 48 |
16 |
32 |
ETDM2_IN_BE |
I2S IN |
TDM (Direct Path) |
Master/Slave |
8 ~ 48 |
16 |
32 |
ETDM2_IN_BE |
PMIC DL |
8 ~ 192 |
2 |
24 |
DL_SRC_BE |
||
PMIC UL |
8 ~ 192 |
2 |
24 |
UL_SRC1_BE/UL_SRC2_BE |
||
PDM1 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM2 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM3 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PDM4 |
Master |
8, 16, 32, 48 |
2 |
24 |
DMIC_BE |
|
PCM (with SRC) |
Master/Slave |
8, 16, 32, 44.1, 48 |
2 |
24 |
PCM1_BE |
|
SPDIF OUT |
Master |
32, 44.1, 48, 88.2, 96, 192 |
2 |
24 |
||
SPDIF IN |
Slave |
32, 44.1, 48, 88.2, 96, 176.4, 192 |
2 |
24 |
||
AUDIO IN |
Slave |
8 ~ 192 |
8 |
24 |
||
HDMIRX |
Slave |
192 |
8 |
24 |
MULTI_IN1_BE |
|
HDMITX |
Master |
8 ~ 192 |
8 |
32 |
ETDM3_OUT_BE |
|
DPTX |
Master |
8 ~ 192 |
8 |
24 |
DPTX_BE |
MT6365 is a power management system chip optimized for handsets and smart phones. This codec is used with the MT8370, MT8390, or MT8395 on the MediaTek platform. The following table will show the interfaces present on the PMIC MT6365.
Audio Interfaces |
Master/Slave |
Sample Rate (kHz) |
Channel Count |
Maximum Bit Resolution |
---|---|---|---|---|
ACCDET |
NA |
NA |
NA |
NA |
Playback (Earphone) |
Master |
8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48, 96, 192 |
2 |
24 |
Playback (Speaker) |
Master |
8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48, 96, 192 |
1 |
24 |
Record (Earphone) |
Master |
8, 16, 32, 48, 96, 192 |
2 |
24 |
Record (AMIC) |
Master |
8, 16, 32, 48, 96, 192 |
3 |
24 |