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  • 高通Audio中ASOC的codec驱动(二)

    继上一篇文章:高通Audio中ASOC的machine驱动(一)

    ASOC的出现是为了让codec独立于CPU,减少和CPU之间的耦合,这样同一个codec驱动就无需修改就可以匹配任何一款平台。

    在Machine中已经知道,snd_soc_dai_link结构就指明了该Machine所使用的Platform和Codec。在Codec这边通过codec_dai和Platform侧的cpu_dai相互通信,既然相互通信,就需要遵守一定的规则,其中codec_dai和cpu_dai统一抽象为struct snd_soc_dai结构,而将dai的相关操作使用snd_soc_dai_driver抽象。同时也需要对所有的codec设备进行抽象封装,linux使用snd_soc_codec进行所有codec设备的抽象,而将codec的驱动抽象为snd_soc_codec_driver结构。
     
     

    1、重要的数据结构:

    所有简单来说,Codec侧有四个重要的数据结构:
     
    struct snd_soc_dai,struct snd_soc_dai_driver,struct snd_soc_codec,struct snd_soc_codec_driver
     
    snd_soc_dai:
     1 /*
     2  * Digital Audio Interface runtime data.
     3  *
     4  * Holds runtime data for a DAI.
     5  */
     6 struct snd_soc_dai {
     7     const char *name;  /* dai的名字 */
     8     struct device *dev;  /* 设备指针 */
     9 
    10     /* driver ops */
    11     struct snd_soc_dai_driver *driver;  /* 指向dai驱动结构的指针 */
    12 
    13     /* DAI runtime info */
    14     unsigned int capture_active:1;        /* stream is in use */
    15     unsigned int playback_active:1;        /* stream is in use */
    16 
    17     /* DAI DMA data */
    18     void *playback_dma_data;  /* 用于管理playback dma */
    19     void *capture_dma_data;  /* 用于管理capture dma */
    20 
    21     /* parent platform/codec */
    22     union {
    23         struct snd_soc_platform *platform;  /* 如果是cpu dai,指向所绑定的平台 */
    24         struct snd_soc_codec *codec;  /* 如果是codec dai指向所绑定的codec */
    25     };
    26     struct snd_soc_card *card;  /* 指向Machine驱动中的crad实例 */
    27 };

    snd_soc_dai_driver:

     1 /*
     2  * Digital Audio Interface Driver.
     3  *
     4  * Describes the Digital Audio Interface in terms of its ALSA, DAI and AC97
     5  * operations and capabilities. Codec and platform drivers will register this
     6  * structure for every DAI they have.
     7  *
     8  * This structure covers the clocking, formating and ALSA operations for each
     9  * interface.
    10  */
    11 struct snd_soc_dai_driver {
    12     /* DAI description */
    13     const char *name;  /* dai驱动名字 */
    14 
    15     /* DAI driver callbacks */
    16     int (*probe)(struct snd_soc_dai *dai);  /* dai驱动的probe函数,由snd_soc_instantiate_card回调 */
    17     int (*remove)(struct snd_soc_dai *dai);  
    18     int (*suspend)(struct snd_soc_dai *dai);  /* 电源管理 */
    19     int (*resume)(struct snd_soc_dai *dai);  
    20 
    21     /* ops */
    22     const struct snd_soc_dai_ops *ops;  /* 指向本dai的snd_soc_dai_ops结构 */
    23 
    24     /* DAI capabilities */
    25     struct snd_soc_pcm_stream capture;  /* 描述capture的能力 */
    26     struct snd_soc_pcm_stream playback;  /* 描述playback的能力 */
    27 };
    snd_soc_codec
     1 /* SoC Audio Codec device */
     2 struct snd_soc_codec {
     3     const char *name;  /* Codec的名字*/
     4     struct device *dev; /* 指向Codec设备的指针 */
     5     const struct snd_soc_codec_driver *driver; /* 指向该codec的驱动的指针 */
     6     struct snd_soc_card *card;    /* 指向Machine驱动的card实例 */
     7     int num_dai; /* 该Codec数字接口的个数,目前越来越多的Codec带有多个I2S或者是PCM接口 */
     8     int (*volatile_register)(...);  /* 用于判定某一寄存器是否是volatile */
     9     int (*readable_register)(...);  /* 用于判定某一寄存器是否可读 */
    10     int (*writable_register)(...);  /* 用于判定某一寄存器是否可写 */
    11 
    12     /* runtime */
    13     ......
    14     /* codec IO */
    15     void *control_data; /* 该指针指向的结构用于对codec的控制,通常和read,write字段联合使用 */
    16     enum snd_soc_control_type control_type;/* 可以是SND_SOC_SPI,SND_SOC_I2C,SND_SOC_REGMAP中的一种 */
    17     unsigned int (*read)(struct snd_soc_codec *, unsigned int);  /* 读取Codec寄存器的函数 */
    18     int (*write)(struct snd_soc_codec *, unsigned int, unsigned int);  /* 写入Codec寄存器的函数 */
    19     /* dapm */
    20     struct snd_soc_dapm_context dapm;  /* 用于DAPM控件 */
    21 };

    snd_soc_codec_driver:

     1 /* codec driver */
     2 struct snd_soc_codec_driver {
     3     /* driver ops */
     4     int (*probe)(struct snd_soc_codec *);  /* codec驱动的probe函数,由snd_soc_instantiate_card回调 */
     5     int (*remove)(struct snd_soc_codec *);  
     6     int (*suspend)(struct snd_soc_codec *);  /* 电源管理 */
     7     int (*resume)(struct snd_soc_codec *);  /* 电源管理 */
     8 
     9     /* Default control and setup, added after probe() is run */
    10     const struct snd_kcontrol_new *controls;  /* 音频控件指针 */
    11     const struct snd_soc_dapm_widget *dapm_widgets;  /* dapm部件指针 */
    12     const struct snd_soc_dapm_route *dapm_routes;  /* dapm路由指针 */
    13 
    14     /* codec wide operations */
    15     int (*set_sysclk)(...);  /* 时钟配置函数 */
    16     int (*set_pll)(...);  /* 锁相环配置函数 */
    17 
    18     /* codec IO */
    19     unsigned int (*read)(...);  /* 读取codec寄存器函数 */
    20     int (*write)(...);  /* 写入codec寄存器函数 */
    21     int (*volatile_register)(...);  /* 用于判定某一寄存器是否是volatile */
    22     int (*readable_register)(...);  /* 用于判定某一寄存器是否可读 */
    23     int (*writable_register)(...);  /* 用于判定某一寄存器是否可写 */
    24 
    25     /* codec bias level */
    26     int (*set_bias_level)(...);  /* 偏置电压配置函数 */
    27 
    28 };

    2、Codec代码分析:

    2.1 找到codec的代码:

    如何找到codec的代码呢?  答案是通过machine中的snd_soc_dai_link结构:
     1 {
     2         .name = LPASS_BE_TERT_MI2S_TX,
     3         .stream_name = "Tertiary MI2S Capture",
     4         .cpu_dai_name = "msm-dai-q6-mi2s.2",
     5         .platform_name = "msm-pcm-routing",
     6         .codec_name     = MSM8X16_CODEC_NAME,
     7         .codec_dai_name = "msm8x16_wcd_i2s_tx1",
     8         .no_pcm = 1,
     9         .be_id = MSM_BACKEND_DAI_TERTIARY_MI2S_TX,
    10         .be_hw_params_fixup = msm_tx_be_hw_params_fixup,
    11         .ops = &msm8x16_mi2s_be_ops,
    12         .ignore_suspend = 1,
    13 },

    由dai_link中codec_name,可以知道我们的codec驱动在哪。

    高通Audio中ASOC的machine驱动这篇文章中的匹配并注册相应驱动的那一章分析可知,codec驱动代码就是msm8x16-wcd.c这个文件;

    3、查看codec的probe函数:

    因为Codec驱动的代码要做到平台无关性,要使得Machine驱动能够使用该Codec,Codec驱动的首要任务就是确定snd_soc_codec和snd_soc_dai的实例,并把它们注册到系统中,注册后的codec和dai才能为Machine驱动所用。
      1 static int msm8x16_wcd_spmi_probe(struct spmi_device *spmi)
      2 {
      3     int ret = 0;
      4     struct msm8x16_wcd *msm8x16 = NULL;
      5     struct msm8x16_wcd_pdata *pdata;
      6     struct resource *wcd_resource;
      7     int modem_state;
      8 
      9     dev_dbg(&spmi->dev, "%s(%d):slave ID = 0x%x
    ",
     10         __func__, __LINE__,  spmi->sid);
     11 
     12     modem_state = apr_get_modem_state();
     13     if (modem_state != APR_SUBSYS_LOADED) {
     14         dev_dbg(&spmi->dev, "Modem is not loaded yet %d
    ",
     15                 modem_state);
     16         return -EPROBE_DEFER;
     17     }
     18 
     19     wcd_resource = spmi_get_resource(spmi, NULL, IORESOURCE_MEM, 0);
     20     if (!wcd_resource) {
     21         dev_err(&spmi->dev, "Unable to get Tombak base address
    ");
     22         return -ENXIO;
     23     }
     24 
     25     switch (wcd_resource->start) {
     26     case TOMBAK_CORE_0_SPMI_ADDR:
     27         msm8x16_wcd_modules[0].spmi = spmi;
     28         msm8x16_wcd_modules[0].base = (spmi->sid << 16) +
     29                         wcd_resource->start;
     30         wcd9xxx_spmi_set_dev(msm8x16_wcd_modules[0].spmi, 0);
     31         device_init_wakeup(&spmi->dev, true);
     32         break;
     33     case TOMBAK_CORE_1_SPMI_ADDR:
     34         msm8x16_wcd_modules[1].spmi = spmi;
     35         msm8x16_wcd_modules[1].base = (spmi->sid << 16) +
     36                         wcd_resource->start;
     37         wcd9xxx_spmi_set_dev(msm8x16_wcd_modules[1].spmi, 1);
     38     if (wcd9xxx_spmi_irq_init()) {
     39         dev_err(&spmi->dev,
     40                 "%s: irq initialization failed
    ", __func__);
     41     } else {
     42         dev_dbg(&spmi->dev,
     43                 "%s: irq initialization passed
    ", __func__);
     44     }
     45         goto rtn;
     46     default:
     47         ret = -EINVAL;
     48         goto rtn;
     49     }
     50 
     51 
     52     dev_dbg(&spmi->dev, "%s(%d):start addr = 0x%pa
    ",
     53         __func__, __LINE__,  &wcd_resource->start);
     54 
     55     if (wcd_resource->start != TOMBAK_CORE_0_SPMI_ADDR)
     56         goto rtn;
     57 
     58     dev_set_name(&spmi->dev, "%s", MSM8X16_CODEC_NAME);
     59     if (spmi->dev.of_node) {
     60         dev_dbg(&spmi->dev, "%s:Platform data from device tree
    ",
     61             __func__);
     62         pdata = msm8x16_wcd_populate_dt_pdata(&spmi->dev);
     63         spmi->dev.platform_data = pdata;
     64     } else {
     65         dev_dbg(&spmi->dev, "%s:Platform data from board file
    ",
     66             __func__);
     67         pdata = spmi->dev.platform_data;
     68     }
     69 
     70     msm8x16 = kzalloc(sizeof(struct msm8x16_wcd), GFP_KERNEL);
     71     if (msm8x16 == NULL) {
     72         dev_err(&spmi->dev,
     73             "%s: error, allocation failed
    ", __func__);
     74         ret = -ENOMEM;
     75         goto rtn;
     76     }
     77 
     78     msm8x16->dev = &spmi->dev;
     79     msm8x16->read_dev = __msm8x16_wcd_reg_read;
     80     msm8x16->write_dev = __msm8x16_wcd_reg_write;
     81     ret = msm8x16_wcd_init_supplies(msm8x16, pdata);
     82     if (ret) {
     83         dev_err(&spmi->dev, "%s: Fail to enable Codec supplies
    ",
     84             __func__);
     85         goto err_codec;
     86     }
     87 
     88     ret = msm8x16_wcd_enable_static_supplies(msm8x16, pdata);
     89     if (ret) {
     90         dev_err(&spmi->dev,
     91             "%s: Fail to enable Codec pre-reset supplies
    ",
     92                __func__);
     93         goto err_codec;
     94     }
     95     usleep_range(5, 6);
     96 
     97     ret = msm8x16_wcd_device_init(msm8x16);
     98     if (ret) {
     99         dev_err(&spmi->dev,
    100             "%s:msm8x16_wcd_device_init failed with error %d
    ",
    101             __func__, ret);
    102         goto err_supplies;
    103     }
    104     dev_set_drvdata(&spmi->dev, msm8x16);
    105 
    106     ret = snd_soc_register_codec(&spmi->dev, &soc_codec_dev_msm8x16_wcd,
    107                      msm8x16_wcd_i2s_dai,
    108                      ARRAY_SIZE(msm8x16_wcd_i2s_dai));
    109     if (ret) {
    110         dev_err(&spmi->dev,
    111             "%s:snd_soc_register_codec failed with error %d
    ",
    112             __func__, ret);
    113     } else {
    114         goto rtn;
    115     }
    116 err_supplies:
    117     msm8x16_wcd_disable_supplies(msm8x16, pdata);
    118 err_codec:
    119     kfree(msm8x16);
    120 rtn:
    121     return ret;
    122 }
    msm8x16_wcd_spmi_probe

    SPMI总线是高通电源管理的一种规范,也就是通过PMU控制音频(具体我也不够了解,有待以后深入理解)

    看看最重要的函数:

    1 ret = snd_soc_register_codec(&spmi->dev, &soc_codec_dev_msm8x16_wcd,
    2                      msm8x16_wcd_i2s_dai,
    3                      ARRAY_SIZE(msm8x16_wcd_i2s_dai));

    此函数通过snd_soc_register_codec函数注册了wcd9320的codec,同时传入了snd_soc_codec_driversnd_soc_dai_driver结构。

     1 static struct snd_soc_codec_driver soc_codec_dev_msm8x16_wcd = {
     2     .probe    = msm8x16_wcd_codec_probe,  /*codec驱动的probe函数,由snd_soc_instantiate_card回调*/
     3     .remove    = msm8x16_wcd_codec_remove,
     4 
     5     .read = msm8x16_wcd_read,
     6     .write = msm8x16_wcd_write,
     7 
     8     .suspend = msm8x16_wcd_suspend,    /*电源管理*/
     9     .resume = msm8x16_wcd_resume,     /*电源管理*/
    10 
    11     .readable_register = msm8x16_wcd_readable,
    12     .volatile_register = msm8x16_wcd_volatile,
    13 
    14     .reg_cache_size = MSM8X16_WCD_CACHE_SIZE,
    15     .reg_cache_default = msm8x16_wcd_reset_reg_defaults,
    16     .reg_word_size = 1,
    17 
    18     .controls = msm8x16_wcd_snd_controls,    
    19     .num_controls = ARRAY_SIZE(msm8x16_wcd_snd_controls),
    20     .dapm_widgets = msm8x16_wcd_dapm_widgets,
    21     .num_dapm_widgets = ARRAY_SIZE(msm8x16_wcd_dapm_widgets),
    22     .dapm_routes = audio_map,
    23     .num_dapm_routes = ARRAY_SIZE(audio_map),
    24 };
     snd_soc_dai_driver结构:
     1 static struct snd_soc_dai_driver msm8x16_wcd_i2s_dai[] = {
     2     {
     3         .name = "msm8x16_wcd_i2s_rx1",
     4         .id = AIF1_PB,
     5         .playback = {
     6             .stream_name = "AIF1 Playback",
     7             .rates = MSM8X16_WCD_RATES,
     8             .formats = MSM8X16_WCD_FORMATS,
     9             .rate_max = 192000,
    10             .rate_min = 8000,
    11             .channels_min = 1,
    12             .channels_max = 3,
    13         },
    14         .ops = &msm8x16_wcd_dai_ops,
    15     },
    16     {
    17         .name = "msm8x16_wcd_i2s_tx1",
    18         .id = AIF1_CAP,
    19         .capture = {
    20             .stream_name = "AIF1 Capture",
    21             .rates = MSM8X16_WCD_RATES,
    22             .formats = MSM8X16_WCD_FORMATS,
    23             .rate_max = 192000,
    24             .rate_min = 8000,
    25             .channels_min = 1,
    26             .channels_max = 4,
    27         },
    28         .ops = &msm8x16_wcd_dai_ops,
    29     },
    30 };

    4、snd_soc_register_codec函数分析:

    首先,它申请了一个snd_soc_codec结构的实例:
     
    1 codec = kzalloc(sizeof(struct snd_soc_codec), GFP_KERNEL);
    确定codec的名字,这个名字很重要,Machine驱动定义的snd_soc_dai_link中会指定每个link的codec和dai的名字,进行匹配绑定时就是通过和这里的名字比较,从而找到该Codec的!
    1 codec->name = fmt_single_name(dev, &codec->id);
    然后初始化它的各个字段,多数字段的值来自上面定义的snd_soc_codec_driver的实例:
     1     codec->write = codec_drv->write;
     2     codec->read = codec_drv->read;
     3     codec->volatile_register = codec_drv->volatile_register;
     4     codec->readable_register = codec_drv->readable_register;
     5     codec->writable_register = codec_drv->writable_register;
     6     codec->ignore_pmdown_time = codec_drv->ignore_pmdown_time;
     7     codec->dapm.bias_level = SND_SOC_BIAS_OFF;
     8     codec->dapm.dev = dev;
     9     codec->dapm.codec = codec;
    10     codec->dapm.seq_notifier = codec_drv->seq_notifier;
    11     codec->dapm.stream_event = codec_drv->stream_event;
    12     codec->dev = dev;
    13     codec->driver = codec_drv;
    14     codec->num_dai = num_dai;
     
    在做了一些寄存器缓存的初始化和配置工作后,通过snd_soc_register_dais函数对本Codec的dai进行注册:
    1 /* register any DAIs */
    2 ret = snd_soc_register_dais(dev, dai_drv, num_dai);
    3 if (ret < 0) {
    4         dev_err(codec->dev, "ASoC: Failed to regster DAIs: %d
    ", ret);
    5         goto fail_codec_name;
    6 }

    它把codec实例链接到全局链表codec_list中:

    1 mutex_lock(&client_mutex);
    2 list_add(&codec->list, &codec_list);
    3 mutex_unlock(&client_mutex);

     并且调用snd_soc_instantiate_cards对machine驱动进行一次匹配绑定的操作;

     

     至此,codec的注册就分析完毕。

    关于codec侧驱动总结:
    1.   分配名字为"codec_name"的平台驱动,注册。
    2.   定义struct snd_soc_codec_driver结构,设置,初始化。
    3.   定义struct snd_soc_dai_driver结构,设置,初始化。
    4.   调用snd_soc_register_codec函数注册codec。
     
     
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  • 原文地址:https://www.cnblogs.com/linhaostudy/p/8425337.html
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