SDAA199 December   2025 AM620-Q1 , AM625 , AM625-Q1 , AM62A3 , AM62A3-Q1 , AM62A7 , AM62A7-Q1 , AM62P , AM62P-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Software Architecture
  6. 3 Sound Card Information
  7. 4 McASP - External Signals
  8. 5 MCASP Clock Generation and Configurations
  9. 6 Dummy Sound Card DTS Changes
  10. 7 Single DAI Link or a Single Sound Card
  11. 8 Multiple DAI Links - Single Card but Multiple Sub-Devices
  12. 9 MCASP - Practical Examples
  13. 10McASP as a Receiver
    1. 10.1 ADC or Codec as Clock Master
    2. 10.2 Device Tree Changes - Codec as Master and MCASP as Slave
  14. 11MCASP as Transmitter
    1. 11.1 Device Tree Changes - With Codec as Slave and MCASP as Master
  15. 12References

2 Software Architecture

The Advanced Linux Sound Architecture (ALSA), now the most popular architecture in Linux system, provides audio and MIDI functionality to the Linux operating system.

ALSA has the following significant features:

  • Efficient support for all types of audio interfaces, from consumer sound cards to professional multichannel audio interfaces.
  • Fully modularized sound drivers.
  • SMP and thread-safe design.
  • User space library (alsa-lib) to simplify application programming and provide higher level functionality.
  • Support for the older Open Sound System (OSS) API, providing binary compatibility for most OSS programs.

ALSA System on Chip (ASoC) layer is designed for SoC audio. The overall project goal of the ASoC layer provides better ALSA support for embedded system on chip processors and portable audio CODECs.

The ASoC layer also provides the following features:

  • CODEC independence. Allows reuse of CODEC drivers on other platforms and machines.
  • Easy I2S/PCM audio interface setup between CODEC and SoC. Each SoC interface and CODEC registers its audio interface capabilities with the core.
  • Dynamic Audio Power Management (DAPM). DAPM is an ASoC technology designed to minimize audio subsystem power consumption no matter what audio-use case is active. DAPM guarantees the lowest audio power state at all times and is completely transparent to user space audio components. DAPM is ideal for mobile devices or devices with complex audio requirements.
  • Pop and click reduction. Pops and clicks can be reduced by powering the CODEC up/down in the correct sequence (including using digital mute). ASoC signals the CODEC when to change power states.
  • Machine-specific controls. Allow machines to add controls to the sound card, for example, volume control for speaker amp.

ASOC Architecture Figure 2-1 ASOC Architecture

ASoC splits an embedded audio system into multiple re-usable component drivers:

  • Codec class drivers: The codec class driver is platform independent and contains audio controls, audio interface capabilities, codec DAPM definition and codec IO functions. This class extends to BT, FM and MODEM ICs if required. Codec class drivers should be generic code that can run on any architecture and machine.
  • Platform class drivers: The platform class driver includes the audio DMA engine driver, digital audio interface (DAI) drivers (e.g. I2S, AC97, PCM) and any audio DSP drivers for that platform.
  • Machine class driver: The machine driver class acts as the glue that describes and binds the other component drivers together to form an ALSA “sound card device”. It handles any machine specific controls and machine level audio events (e.g. turning on an amp at start of playback).

More detailed information about ASoC can be found in the Linux kernel documentation in the Linux OS source tree at linux/Documentation/sound/alsa/soc and at www.alsa-project.org/main/index.php/ASoC.