Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 78 insertions, 0 deletions

diff --git a/Documentation/sound/soc/platform.rst b/Documentation/sound/soc/platform.rst
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+====================
+ASoC Platform Driver
+====================
+
+An ASoC platform driver class can be divided into audio DMA drivers, SoC DAI
+drivers and DSP drivers. The platform drivers only target the SoC CPU and must
+have no board specific code.
+
+Audio DMA
+=========
+
+The platform DMA driver optionally supports the following ALSA operations:-
+::
+
+  /* SoC audio ops */
+  struct snd_soc_ops {
+	int (*startup)(struct snd_pcm_substream *);
+	void (*shutdown)(struct snd_pcm_substream *);
+	int (*hw_params)(struct snd_pcm_substream *, struct snd_pcm_hw_params *);
+	int (*hw_free)(struct snd_pcm_substream *);
+	int (*prepare)(struct snd_pcm_substream *);
+	int (*trigger)(struct snd_pcm_substream *, int);
+  };
+
+The platform driver exports its DMA functionality via struct
+snd_soc_component_driver:-
+::
+
+  struct snd_soc_component_driver {
+	const char *name;
+
+	...
+	int (*probe)(struct snd_soc_component *);
+	void (*remove)(struct snd_soc_component *);
+	int (*suspend)(struct snd_soc_component *);
+	int (*resume)(struct snd_soc_component *);
+
+	/* pcm creation and destruction */
+	int (*pcm_new)(struct snd_soc_pcm_runtime *);
+	void (*pcm_free)(struct snd_pcm *);
+
+	...
+	const struct snd_pcm_ops *ops;
+	const struct snd_compr_ops *compr_ops;
+	...
+  };
+
+Please refer to the ALSA driver documentation for details of audio DMA.
+http://www.alsa-project.org/~iwai/writing-an-alsa-driver/
+
+An example DMA driver is soc/pxa/pxa2xx-pcm.c
+
+
+SoC DAI Drivers
+===============
+
+Each SoC DAI driver must provide the following features:-
+
+1. Digital audio interface (DAI) description
+2. Digital audio interface configuration
+3. PCM's description
+4. SYSCLK configuration
+5. Suspend and resume (optional)
+
+Please see codec.rst for a description of items 1 - 4.
+
+
+SoC DSP Drivers
+===============
+
+Each SoC DSP driver usually supplies the following features :-
+
+1. DAPM graph
+2. Mixer controls
+3. DMA IO to/from DSP buffers (if applicable)
+4. Definition of DSP front end (FE) PCM devices.
+
+Please see DPCM.txt for a description of item 4.