[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
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+=======================
+ALSA SoC Layer Overview
+=======================
+
+The overall project goal of the ALSA System on Chip (ASoC) layer is to
+provide better ALSA support for embedded system-on-chip processors (e.g.
+pxa2xx, au1x00, iMX, etc) and portable audio codecs. Prior to the ASoC
+subsystem there was some support in the kernel for SoC audio, however it
+had some limitations:-
+
+ * Codec drivers were often tightly coupled to the underlying SoC
+ CPU. This is not ideal and leads to code duplication - for example,
+ Linux had different wm8731 drivers for 4 different SoC platforms.
+
+ * There was 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 often require
+ machine specific code to re-route audio, enable amps, etc., after such an
+ event.
+
+ * Drivers tended 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 was 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 its audio interface capabilities with the
+ core and are subsequently matched and configured when the application
+ hardware parameters are known.
+
+ * Dynamic Audio Power Management (DAPM). DAPM automatically sets the codec to
+ its 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 amplifier).
+
+To achieve all this, ASoC basically 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).