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+ALSA SoC Layer
+==============
+
+The overall project goal of the ALSA System on Chip (ASoC) layer is to provide
+better ALSA support for embedded system on chip procesors (e.g. pxa2xx, au1x00,
+iMX, etc) and portable audio codecs. Currently there is some support in the
+kernel for SoC audio, however it has some limitations:-
+
+ * Currently, codec drivers are often tightly coupled to the underlying SoC
+ cpu. This is not ideal and leads to code duplication i.e. Linux now has 4
+ different wm8731 drivers for 4 different SoC platforms.
+
+ * There is no standard method to signal user initiated audio events.
+ e.g. Headphone/Mic insertion, Headphone/Mic detection after an insertion
+ event. These are quite common events on portable devices and ofter require
+ machine specific code to re route audio, enable amps etc after such an event.
+
+ * Current drivers tend to power up the entire codec when playing
+ (or recording) audio. This is fine for a PC, but tends to waste a lot of
+ power on portable devices. There is also no support for saving power via
+ changing codec oversampling rates, bias currents, etc.
+
+
+ASoC Design
+===========
+
+The ASoC layer is designed to address these issues and provide 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 it's audio interface capabilities with the core and are
+ subsequently matched and configured when the application hw params are known.
+
+ * Dynamic Audio Power Management (DAPM). DAPM automatically sets the codec to
+ it's minimum power state at all times. This includes powering up/down
+ internal power blocks depending on the internal codec audio routing and any
+ active streams.
+
+ * 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
+ e.g. volume control for speaker amp.
+
+To achieve all this, ASoC basically splits an embedded audio system into 3
+components :-
+
+ * Codec driver: The codec driver is platform independent and contains audio
+ controls, audio interface capabilities, codec dapm definition and codec IO
+ functions.
+
+ * Platform driver: The platform driver contains the audio dma engine and audio
+ interface drivers (e.g. I2S, AC97, PCM) for that platform.
+
+ * Machine driver: The machine driver handles any machine specific controls and
+ audio events. i.e. turing on an amp at start of playback.
+
+
+Documentation
+=============
+
+The documentation is spilt into the following sections:-
+
+overview.txt: This file.
+
+codec.txt: Codec driver internals.
+
+DAI.txt: Description of Digital Audio Interface standards and how to configure
+a DAI within your codec and CPU DAI drivers.
+
+dapm.txt: Dynamic Audio Power Management
+
+platform.txt: Platform audio DMA and DAI.
+
+machine.txt: Machine driver internals.
+
+pop_clicks.txt: How to minimise audio artifacts.
+
+clocking.txt: ASoC clocking for best power performance. \ No newline at end of file