From 96boards docsdragonboard/dragonboard410c/guides/enable-ls-i2s.md.html
- Primary MI2S - Supports only playback
- Secondary MI2S - Supports only playback
- Tertiary MI2S - Supports only capture
- Quatenary MI2S - Supports both playback and capture
Primary and Secondary I2S interfaces are connected to External Primary TLMM via Mux1. Teritary and Quatenary I2S interfaces are connected to External Secondary TLMM via Mux2.
By default, internal WCD codec in APQ8016 occupies Primary MI2S for playback and Teritary MI2S for capture. On the other hand, external codec (ADV7533) present on the Dragonboard410c occupies Quatenary MI2S for playback.
NOTE: As far as I can tell SDM845 is not at all similar to this
The DT sound node defines available links and routing between sources/sinks. The hardware has 8 "mixers", MultiMedia[1..8]
CPU, platform and codec DAIs are defined in the sound node. Summary can be found in this nice article
The CPU DAI handles physical audio links - like a PHY (?). It does I2S, SPDIF, PCM etc...
The codec DAI handles audio controls, volume, mixing, routing etc.
The platform DAI does stuff like audio DMA? On sdm845 it's for q6routing for SLIM and MI2s devices.
MultiMedia[1..8] are the "endpoints" which show up as capture/playback devices in userspace, controls are mixed to them, e.g.
QUATERNARY_MI2S Audio Mixer MultiMedia1 - enables routing sound playback into MultiMedia1 to the QUAT MI2S interface.
For capture it would be MultiMedia1 Audio Mixer QUATERNARY_MI2S
Worth noting that RX on the codec represents a playback device, e.g. SLIM_RX0.
7 SLIMBUS RX channels (for playback)
- RX0 - Earpiece
- RX1 - Headphone Left
- RX2 - Headphone Right
- RX3 - Hifi LineOut 1
- RX4 - Hifi LineOut 2
- RX5/6 - N/A ?
- RX7 - Speaker left out PA (unused on most form factor devices)
- RX8 - Speaker right out PA
I'm not sure if all of these are needed, it's also possible that RXn refers to something different than above? Without access to the WCD934x docs we can't know how the muxes, routing and interfaces work entirely.
| Control | Value |
|---|---|
| SLIM RX0 MUX | AIF1_PB |
| SLIM RX1 MUX | AIF1_PB |
| SLIM RX2 MUX | AIF1_PB |
| SLIM RX3 MUX | AIF1_PB |
For earpiece playback from AIF1_PB the following controls must be set:
| Control | Value |
|---|---|
| RX INT0_1 MIX1 INP0 | RX0 |
| RX INT0 DEM MUX | CLSH_DSM_OUT |
| RX INT0_1 INTERP | RX INT0_1 MIX1 |
volume can be set with the RX0 Digital Volume control
Downstream seems to make use of the AIF_PB4 playback interface on the wcd934x codec for the headphones (AIF1 for the earpiece?), I'm not sure how to represent that nicely on mainline, perhaps we could use MultiMedia4 and route that. For now the headphone configuration is pretty weird.
According to the kernel driver, RX1 and RX2 are for headphones, but both here and in downstream we reference RX2 and RX3, I don't fully understand these controls.
| Control | Value |
|---|---|
| RX INT1 DEM MUX | CLSH_DSM_OUT |
| RX INT2 DEM MUX | CLSH_DSM_OUT |
| RX INT1_1 INTERP | RX INT1_1 MIX1 |
| RX INT2_1 INTERP | RX INT2_1 MIX1 |
| RX INT1_1 MIX1 INP0 | RX2 |
| RX INT2_1 MIX1 INP0 | RX3 |
| RX INT1_2 MUX | RX0 |
| RX INT2_2 MUX | RX1 |
| Acronym | Meaning |
|---|---|
| DAI | Digital Audio Interface |
| I2S | Inter-IC Sound Standard |
| MI2S | Multi-channel Inter-IC Sound Standard |
| SLIMbus | Serial Lower Power Interchip Media Bus |
| DMIC | Digital Microphone Interface |
| AIF | Audio Interface _ |
| TDM | Time Division Multiplexing - multiplex multiple streams into a single sample buffer |