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56f2399f0e
Fixed some spelling issues in documentations. Signed-off-by: Armin Mahdilou <Armin.Mahdilou@gmail.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Link: https://lore.kernel.org/r/20250210192754.30283-1-Armin.Mahdilou@gmail.com
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4.0 KiB
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124 lines
4.0 KiB
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===================
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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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::
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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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::
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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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In the above struct, dai’s are registered using names but you can pass
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either dai name or device tree node but not both. Also, names used here
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for cpu/codec/platform dais should be globally unique.
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Additionally below example macro can be used to register cpu, codec and
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platform dai::
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SND_SOC_DAILINK_DEFS(wm2200_cpu_dsp,
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DAILINK_COMP_ARRAY(COMP_CPU("samsung-i2s.0")),
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DAILINK_COMP_ARRAY(COMP_CODEC("spi0.0", "wm0010-sdi1")),
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DAILINK_COMP_ARRAY(COMP_PLATFORM("samsung-i2s.0")));
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struct snd_soc_card then sets up the machine with its DAIs. e.g.
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::
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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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Following this, ``devm_snd_soc_register_card`` can be used to register
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the sound card. During the registration, the individual components
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such as the codec, CPU, and platform are probed. If all these components
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are successfully probed, the sound card gets registered.
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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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Clocking Controls
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-----------------
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As previously noted, clock configuration is handled within the machine driver.
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For details on the clock APIs that the machine driver can utilize for
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setup, please refer to Documentation/sound/soc/clocking.rst. However, the
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callback needs to be registered by the CPU/Codec/Platform drivers to configure
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the clocks that is needed for the corresponding device operation.
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