alsa Machine、Platform和Codec 驱动实例源码解析（基于am335x）

1840阅读　0评论2020-01-08　fangdikui
分类：LINUX

学习alsa音频驱动过程，一定有了解ASoC被分为Machine、Platform和Codec三大部分。其中的Machine驱动负责Platform和Codec之间的耦合和设备或板子特定的代码。框架的资料网上比较多，具体实例确不多，以致于我看了好多资料，还不知源码中哪一部分属于machine驱动。希望能帮助初学的人

那么这三大部分结合到具体的单板，到底是如何初始化的呢，本文就以am335x为例一步一步解说

machine驱动，用于为目标板绑定正确的platform和codec驱动，完成这个任务的就在soc_bind_dai_link(struct snd_soc_card *card, int num)中，实际上就是将card->rtd的三个重要成员card->rtd->cpu_dai，card->rtd->codec，card->rtd->platform初始化

全文涉及的文有：

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  1. sound\soc\davinci\davinci-evm.c "soc-audio" 设备注册(alsa machine)
  2. sound\soc\soc-core.c "soc-audio" 驱动注册(alsa machine)
  3. sound\soc\davinci\davinci-pcm.c "davinci-pcm-audio" 驱动注册(alsa platform)
  4. arch\arm\mach-omap2\devices.c "davinci-pcm-audio"设备注册 (alsa platform)
  5. sound\soc\codecs\tlv320aic3x.c i2c驱动注册(alsa codec)
  6. arch\arm\mach-omap2\board-am335xevm.c i2c "tlv320aic3x-codec.1-001b"设备注册(alsa codec)
  7. sound\soc\davinci\davinci-mcasp.c "davinci-mcasp" 驱动注册(alsa dai)
  8. arch\arm\mach-omap2\devices.c "davinci-mcasp"设备注册(alsa dai)




 (1)  alsa的machine驱动

sound\soc\davinci\davinci-evm.c     
 

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  1. static struct snd_soc_dai_link am335x_evm_dai = {

  3.          .name = "TLV320AIC3X",

  5.          .stream_name = "AIC3X",

  7.          .cpu_dai_name = "davinci-mcasp.0",//1->0

  9.          .codec_dai_name = "tlv320aic3x-hifi",

  11.          .codec_name = "tlv320aic3x-codec.1-001b",//2->1

  13.          .platform_name = "davinci-pcm-audio",

  15.          .init = evm_aic3x_init,

  17.          .ops = &evm_ops,

  19. };

  21. static struct snd_soc_card am335x_snd_soc_card = {

  23.          .name = "AM335X EVM",

  25.          .dai_link = &am335x_evm_dai,

  27.          .num_links = 1,

  29. };

  31. evm_init(){

  33.   evm_snd_dev_data = &am335x_snd_soc_card;

  35.   evm_snd_device = platform_device_alloc("soc-audio", index);

  37.   platform_set_drvdata(evm_snd_device, evm_snd_dev_data);

  39.   platform_device_add(evm_snd_device);

  41. }
   


这将触发"soc-audio"平台设备驱动的probe函数，这在soc-core.c中

sound\soc\soc-core.c                                                                 


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  1. static struct platform_driver soc_driver = {

  3.          .driver = {

  5.                    .name = "soc-audio",

  7.                    .owner = THIS_MODULE,

  9.                    .pm = &snd_soc_pm_ops,

  11.          },

  13.          .probe = soc_probe,

  15.          .remove = soc_remove,

  17. };

  19. soc_probe(){

  21.   snd_soc_register_card(am335x_snd_soc_card){

  23.     card->rtd = kzalloc()

  25.     snd_soc_instantiate_cards()

  27.     snd_soc_instantiate_card()

  29.       soc_bind_dai_link(){

  31.       rtd->cpu_dai [find cpu_dai_name == davinci-mcasp.0]

  33.       rtd->codec [find codec_name == tlv320aic3x-codec.1-001b]

  35.       rtd->platform [find platform_name == davinci-pcm-audio]

  37.   }

  39. }



在soc_bind_dai_link找到合适的cpu_dai, codec, platform,具体查找过程看源码比较好理解，就是分别从dai_list ,codec_list，platform_list链表中找到名字相同的项，接下来就是理清这三个list是如何被add的就可以了

 (2) alsa的platform驱动 (platform_list)

从soc_bind_dai_link()中可以看出，一定有一个名为davinci-pcm-audio的alsa platform驱动，经过搜索snd_soc_register_platform()完成platform_list的add操作

 

sound\soc\davinci\davinci-pcm.c  davinci-pcm-audio驱动注册

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  1. static struct platform_driver davinci_pcm_driver = {

  3.          .driver = {

  5.                             .name = "davinci-pcm-audio",

  7.                             .owner = THIS_MODULE,

  9.          },

  11.          .probe = davinci_soc_platform_probe,

  13.          .remove = __devexit_p(davinci_soc_platform_remove),

  15. };

  17. static int __init snd_davinci_pcm_init(void)

  19. {

  21.          return platform_driver_register(&davinci_pcm_driver);

  23. }

  25. module_init(snd_davinci_pcm_init);

  27. davinci_soc_platform_probe (){

  29.    snd_soc_register_platform(){

  31.            platform->name = fmt_single_name(dev, &platform->id);// 取出"davinci-pcm-audio",

  33.       list_add(&platform->list, &platform_list);

  35.       snd_soc_instantiate_cards();

  37.    }

  39. }



 

arch\arm\mach-omap2\devices.c    davinci-pcm-audio设备注册

 

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  1. struct platform_device am33xx_pcm_device = {

  3.          .name = "davinci-pcm-audio",

  5.          .id = -1,

  7. };

  9. arch_initcall(omap2_init_devices);

  11. omap2_init_devices(){

  13.   am33xx_init_pcm(){

  15.     platform_device_register(&am33xx_pcm_device);

  17.   }

  19. }

 


(3) alsa的codec驱动 (codec_list)

sound\soc\codecs\tlv320aic3x.c  i2c驱动注册

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  1. aic3x_modinit(){

  3.          i2c_add_driver(&aic3x_i2c_driver);

  5.        aic3x_i2c_probe(){

  7.          ret = snd_soc_register_codec(&i2c->dev,&soc_codec_dev_aic3x, &aic3x_dai, 1){

  9.          codec->name = fmt_single_name(dev, &codec->id);

  11.          list_add(&codec->list, &codec_list);

  13.          }

  15.        }

  17. }

  19. arch\arm\mach-omap2\board-am335xevm.c i2c tlv320aic3x-codec.1-001b设备注册



  23. static struct evm_dev_cfg evm_sk_dev_cfg[] = {

  25.                   {i2c0_init, DEV_ON_BASEBOARD, PROFILE_ALL},

  27. };

  29. am335x_evm_init(){

  31.   am335x_evm_setup(){

  33.     setup_starterkit(){

  35.       _configure_device(EVM_SK, evm_sk_dev_cfg, PROFILE_NONE);

  37.     }

  39.   }

  41. }

  43. static struct i2c_board_info __initdata am335x_i2c0_boardinfo[] = {

  45.          {

  47.                    I2C_BOARD_INFO("tlv320aic3x", 0x1b),

  49.          },

  51. };

  53. static void i2c0_init(int evm_id, int profile)

  55. {

  57.   omap_register_i2c_bus(1, 100, am335x_i2c0_boardinfo,ARRAY_SIZE(am335x_i2c0_boardinfo));

  59. }



(4) alsa的dai驱动 dai_list

sound\soc\davinci\davinci-mcasp.c  "davinci-mcasp" 驱动

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  1. static struct snd_soc_dai_driver davinci_mcasp_dai[] = {

  3.          {

  5.                    .name = "davinci-mcasp.0",

  7.                    .playback = {

  9.                             .channels_min = 2,

  11.                             .channels_max = 2,

  13.                             .rates = DAVINCI_MCASP_RATES,

  15.                             .formats = DAVINCI_MCASP_PCM_FMTS,

  17.                    },

  19.                    .capture = {

  21.                             .channels_min = 2,

  23.                             .channels_max = 2,

  25.                             .rates = DAVINCI_MCASP_RATES,

  27.                             .formats = DAVINCI_MCASP_PCM_FMTS,

  29.                    },

  31.                    .ops = &davinci_mcasp_dai_ops,

  33.  

  35.          },

  37.  

  39. };

  41.  

  43. static struct platform_driver davinci_mcasp_driver = {

  45.          .probe = davinci_mcasp_probe,

  47.          .remove = davinci_mcasp_remove,

  49. #ifdef CONFIG_PM

  51.          .suspend = davinci_mcasp_suspend,

  53.          .resume = davinci_mcasp_resume,

  55. #endif

  57.          .driver = {

  59.                    .name = "davinci-mcasp",

  61.                    .owner = THIS_MODULE,

  63.          },

  65. };

  67. davinci_mcasp_probe(){

  69.   snd_soc_register_dai(&pdev->dev, &davinci_mcasp_dai[pdata->op_mode]){

  71.     dai->name = fmt_single_name(dev, &dai->id);

  73.       list_add(&dai->list, &dai_list);

  75.            snd_soc_instantiate_cards();

  77.   }

  79. }



arch\arm\mach-omap2\devices.c  "davinci-mcasp"设备

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  1. mcasp0_init(){

  3.   am335x_register_mcasp(&am335x_evm_snd_data0, 0){

  5.   char *dev_name = "davinci-mcasp";

  7.   pdev = omap_device_build(dev_name, ctrl_nr, oh, pdata,

  9.                             sizeof(struct snd_platform_data), NULL, 0, 0);

  11.   }

  13. }



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