94 lines
2.8 KiB
Plaintext
94 lines
2.8 KiB
Plaintext
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ASoC Machine Driver
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===================
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The ASoC machine (or board) driver is the code that glues together all the
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component drivers (e.g. codecs, platforms and DAIs). It also describes the
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relationships between each component which include audio paths, GPIOs,
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interrupts, clocking, jacks and voltage regulators.
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The machine driver can contain codec and platform specific code. It registers
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the audio subsystem with the kernel as a platform device and is represented by
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the following struct:-
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/* SoC machine */
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struct snd_soc_card {
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char *name;
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...
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int (*probe)(struct platform_device *pdev);
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int (*remove)(struct platform_device *pdev);
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/* the pre and post PM functions are used to do any PM work before and
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* after the codec and DAIs do any PM work. */
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int (*suspend_pre)(struct platform_device *pdev, pm_message_t state);
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int (*suspend_post)(struct platform_device *pdev, pm_message_t state);
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int (*resume_pre)(struct platform_device *pdev);
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int (*resume_post)(struct platform_device *pdev);
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...
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/* CPU <--> Codec DAI links */
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struct snd_soc_dai_link *dai_link;
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int num_links;
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...
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};
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probe()/remove()
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----------------
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probe/remove are optional. Do any machine specific probe here.
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suspend()/resume()
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------------------
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The machine driver has pre and post versions of suspend and resume to take care
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of any machine audio tasks that have to be done before or after the codec, DAIs
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and DMA is suspended and resumed. Optional.
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Machine DAI Configuration
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-------------------------
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The machine DAI configuration glues all the codec and CPU DAIs together. It can
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also be used to set up the DAI system clock and for any machine related DAI
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initialisation e.g. the machine audio map can be connected to the codec audio
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map, unconnected codec pins can be set as such.
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struct snd_soc_dai_link is used to set up each DAI in your machine. e.g.
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/* corgi digital audio interface glue - connects codec <--> CPU */
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static struct snd_soc_dai_link corgi_dai = {
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.name = "WM8731",
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.stream_name = "WM8731",
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.cpu_dai_name = "pxa-is2-dai",
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.codec_dai_name = "wm8731-hifi",
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.platform_name = "pxa-pcm-audio",
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.codec_name = "wm8713-codec.0-001a",
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.init = corgi_wm8731_init,
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.ops = &corgi_ops,
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};
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struct snd_soc_card then sets up the machine with its DAIs. e.g.
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/* corgi audio machine driver */
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static struct snd_soc_card snd_soc_corgi = {
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.name = "Corgi",
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.dai_link = &corgi_dai,
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.num_links = 1,
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};
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Machine Power Map
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-----------------
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The machine driver can optionally extend the codec power map and to become an
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audio power map of the audio subsystem. This allows for automatic power up/down
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of speaker/HP amplifiers, etc. Codec pins can be connected to the machines jack
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sockets in the machine init function.
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Machine Controls
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----------------
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Machine specific audio mixer controls can be added in the DAI init function.
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