| rjw | 1f88458 | 2022-01-06 17:20:42 +0800 | [diff] [blame^] | 1 | =================== |
| 2 | ASoC Machine Driver |
| 3 | =================== |
| 4 | |
| 5 | The ASoC machine (or board) driver is the code that glues together all the |
| 6 | component drivers (e.g. codecs, platforms and DAIs). It also describes the |
| 7 | relationships between each component which include audio paths, GPIOs, |
| 8 | interrupts, clocking, jacks and voltage regulators. |
| 9 | |
| 10 | The machine driver can contain codec and platform specific code. It registers |
| 11 | the audio subsystem with the kernel as a platform device and is represented by |
| 12 | the following struct:- |
| 13 | :: |
| 14 | |
| 15 | /* SoC machine */ |
| 16 | struct snd_soc_card { |
| 17 | char *name; |
| 18 | |
| 19 | ... |
| 20 | |
| 21 | int (*probe)(struct platform_device *pdev); |
| 22 | int (*remove)(struct platform_device *pdev); |
| 23 | |
| 24 | /* the pre and post PM functions are used to do any PM work before and |
| 25 | * after the codec and DAIs do any PM work. */ |
| 26 | int (*suspend_pre)(struct platform_device *pdev, pm_message_t state); |
| 27 | int (*suspend_post)(struct platform_device *pdev, pm_message_t state); |
| 28 | int (*resume_pre)(struct platform_device *pdev); |
| 29 | int (*resume_post)(struct platform_device *pdev); |
| 30 | |
| 31 | ... |
| 32 | |
| 33 | /* CPU <--> Codec DAI links */ |
| 34 | struct snd_soc_dai_link *dai_link; |
| 35 | int num_links; |
| 36 | |
| 37 | ... |
| 38 | }; |
| 39 | |
| 40 | probe()/remove() |
| 41 | ---------------- |
| 42 | probe/remove are optional. Do any machine specific probe here. |
| 43 | |
| 44 | |
| 45 | suspend()/resume() |
| 46 | ------------------ |
| 47 | The machine driver has pre and post versions of suspend and resume to take care |
| 48 | of any machine audio tasks that have to be done before or after the codec, DAIs |
| 49 | and DMA is suspended and resumed. Optional. |
| 50 | |
| 51 | |
| 52 | Machine DAI Configuration |
| 53 | ------------------------- |
| 54 | The machine DAI configuration glues all the codec and CPU DAIs together. It can |
| 55 | also be used to set up the DAI system clock and for any machine related DAI |
| 56 | initialisation e.g. the machine audio map can be connected to the codec audio |
| 57 | map, unconnected codec pins can be set as such. |
| 58 | |
| 59 | struct snd_soc_dai_link is used to set up each DAI in your machine. e.g. |
| 60 | :: |
| 61 | |
| 62 | /* corgi digital audio interface glue - connects codec <--> CPU */ |
| 63 | static struct snd_soc_dai_link corgi_dai = { |
| 64 | .name = "WM8731", |
| 65 | .stream_name = "WM8731", |
| 66 | .cpu_dai_name = "pxa-is2-dai", |
| 67 | .codec_dai_name = "wm8731-hifi", |
| 68 | .platform_name = "pxa-pcm-audio", |
| 69 | .codec_name = "wm8713-codec.0-001a", |
| 70 | .init = corgi_wm8731_init, |
| 71 | .ops = &corgi_ops, |
| 72 | }; |
| 73 | |
| 74 | struct snd_soc_card then sets up the machine with its DAIs. e.g. |
| 75 | :: |
| 76 | |
| 77 | /* corgi audio machine driver */ |
| 78 | static struct snd_soc_card snd_soc_corgi = { |
| 79 | .name = "Corgi", |
| 80 | .dai_link = &corgi_dai, |
| 81 | .num_links = 1, |
| 82 | }; |
| 83 | |
| 84 | |
| 85 | Machine Power Map |
| 86 | ----------------- |
| 87 | |
| 88 | The machine driver can optionally extend the codec power map and to become an |
| 89 | audio power map of the audio subsystem. This allows for automatic power up/down |
| 90 | of speaker/HP amplifiers, etc. Codec pins can be connected to the machines jack |
| 91 | sockets in the machine init function. |
| 92 | |
| 93 | |
| 94 | Machine Controls |
| 95 | ---------------- |
| 96 | |
| 97 | Machine specific audio mixer controls can be added in the DAI init function. |