diff options
author | Mark Brown <broonie@opensource.wolfsonmicro.com> | 2008-01-23 02:41:46 -0500 |
---|---|---|
committer | Jaroslav Kysela <perex@perex.cz> | 2008-01-31 11:30:10 -0500 |
commit | 7c4dbbd87c0dc62849f0f72449464dc37da0a82a (patch) | |
tree | 27ea47730466503e9c4e92bebb7a64a9fb5538ea /Documentation/sound/alsa/soc/overview.txt | |
parent | dca008f367586f73bd1c766836e4f7a38ce9814f (diff) |
[ALSA] ASoC documentation updates
Update the ASoC documentation. Along with minor formatting and grammar
cleanups it moves the ASoC overview into the present tense to reflect
the fact that it has now been merged.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Diffstat (limited to 'Documentation/sound/alsa/soc/overview.txt')
-rw-r--r-- | Documentation/sound/alsa/soc/overview.txt | 42 |
1 files changed, 22 insertions, 20 deletions
diff --git a/Documentation/sound/alsa/soc/overview.txt b/Documentation/sound/alsa/soc/overview.txt index c47ce9530677..1e4c6d3655f2 100644 --- a/Documentation/sound/alsa/soc/overview.txt +++ b/Documentation/sound/alsa/soc/overview.txt | |||
@@ -1,25 +1,26 @@ | |||
1 | ALSA SoC Layer | 1 | ALSA SoC Layer |
2 | ============== | 2 | ============== |
3 | 3 | ||
4 | The overall project goal of the ALSA System on Chip (ASoC) layer is to provide | 4 | The overall project goal of the ALSA System on Chip (ASoC) layer is to |
5 | better ALSA support for embedded system-on-chip processors (e.g. pxa2xx, au1x00, | 5 | provide better ALSA support for embedded system-on-chip processors (e.g. |
6 | iMX, etc) and portable audio codecs. Currently there is some support in the | 6 | pxa2xx, au1x00, iMX, etc) and portable audio codecs. Prior to the ASoC |
7 | kernel for SoC audio, however it has some limitations:- | 7 | subsystem there was some support in the kernel for SoC audio, however it |
8 | had some limitations:- | ||
8 | 9 | ||
9 | * Currently, codec drivers are often tightly coupled to the underlying SoC | 10 | * Codec drivers were often tightly coupled to the underlying SoC |
10 | CPU. This is not ideal and leads to code duplication i.e. Linux now has 4 | 11 | CPU. This is not ideal and leads to code duplication - for example, |
11 | different wm8731 drivers for 4 different SoC platforms. | 12 | Linux had different wm8731 drivers for 4 different SoC platforms. |
12 | 13 | ||
13 | * There is no standard method to signal user initiated audio events (e.g. | 14 | * There was no standard method to signal user initiated audio events (e.g. |
14 | Headphone/Mic insertion, Headphone/Mic detection after an insertion | 15 | Headphone/Mic insertion, Headphone/Mic detection after an insertion |
15 | event). These are quite common events on portable devices and often require | 16 | event). These are quite common events on portable devices and often require |
16 | machine specific code to re-route audio, enable amps, etc., after such an | 17 | machine specific code to re-route audio, enable amps, etc., after such an |
17 | event. | 18 | event. |
18 | 19 | ||
19 | * Current drivers tend to power up the entire codec when playing | 20 | * Drivers tended to power up the entire codec when playing (or |
20 | (or recording) audio. This is fine for a PC, but tends to waste a lot of | 21 | recording) audio. This is fine for a PC, but tends to waste a lot of |
21 | power on portable devices. There is also no support for saving power via | 22 | power on portable devices. There was also no support for saving |
22 | changing codec oversampling rates, bias currents, etc. | 23 | power via changing codec oversampling rates, bias currents, etc. |
23 | 24 | ||
24 | 25 | ||
25 | ASoC Design | 26 | ASoC Design |
@@ -31,12 +32,13 @@ features :- | |||
31 | * Codec independence. Allows reuse of codec drivers on other platforms | 32 | * Codec independence. Allows reuse of codec drivers on other platforms |
32 | and machines. | 33 | and machines. |
33 | 34 | ||
34 | * Easy I2S/PCM audio interface setup between codec and SoC. Each SoC interface | 35 | * Easy I2S/PCM audio interface setup between codec and SoC. Each SoC |
35 | and codec registers it's audio interface capabilities with the core and are | 36 | interface and codec registers it's audio interface capabilities with the |
36 | subsequently matched and configured when the application hw params are known. | 37 | core and are subsequently matched and configured when the application |
38 | hardware parameters are known. | ||
37 | 39 | ||
38 | * Dynamic Audio Power Management (DAPM). DAPM automatically sets the codec to | 40 | * Dynamic Audio Power Management (DAPM). DAPM automatically sets the codec to |
39 | it's minimum power state at all times. This includes powering up/down | 41 | its minimum power state at all times. This includes powering up/down |
40 | internal power blocks depending on the internal codec audio routing and any | 42 | internal power blocks depending on the internal codec audio routing and any |
41 | active streams. | 43 | active streams. |
42 | 44 | ||
@@ -45,16 +47,16 @@ features :- | |||
45 | signals the codec when to change power states. | 47 | signals the codec when to change power states. |
46 | 48 | ||
47 | * Machine specific controls: Allow machines to add controls to the sound card | 49 | * Machine specific controls: Allow machines to add controls to the sound card |
48 | (e.g. volume control for speaker amp). | 50 | (e.g. volume control for speaker amplifier). |
49 | 51 | ||
50 | To achieve all this, ASoC basically splits an embedded audio system into 3 | 52 | To achieve all this, ASoC basically splits an embedded audio system into 3 |
51 | components :- | 53 | components :- |
52 | 54 | ||
53 | * Codec driver: The codec driver is platform independent and contains audio | 55 | * Codec driver: The codec driver is platform independent and contains audio |
54 | controls, audio interface capabilities, codec dapm definition and codec IO | 56 | controls, audio interface capabilities, codec DAPM definition and codec IO |
55 | functions. | 57 | functions. |
56 | 58 | ||
57 | * Platform driver: The platform driver contains the audio dma engine and audio | 59 | * Platform driver: The platform driver contains the audio DMA engine and audio |
58 | interface drivers (e.g. I2S, AC97, PCM) for that platform. | 60 | interface drivers (e.g. I2S, AC97, PCM) for that platform. |
59 | 61 | ||
60 | * Machine driver: The machine driver handles any machine specific controls and | 62 | * Machine driver: The machine driver handles any machine specific controls and |
@@ -81,4 +83,4 @@ machine.txt: Machine driver internals. | |||
81 | 83 | ||
82 | pop_clicks.txt: How to minimise audio artifacts. | 84 | pop_clicks.txt: How to minimise audio artifacts. |
83 | 85 | ||
84 | clocking.txt: ASoC clocking for best power performance. \ No newline at end of file | 86 | clocking.txt: ASoC clocking for best power performance. |