Linux声卡驱动分析.doc

Linux soc声卡构架分析（DMA）以S3C2440为例进行分析，对应的文件linux-/sound/soc/s3c24xx/s3c24xx_uda134x.c其中module_init入口内容为：357static int _init s3c24xx_uda134x_init(void)358359return platform_driver_register(&s3c24xx_uda134x_driver);360359行是一个平台驱动的注册函数，注册的驱动是s3c24xx_uda134x_driver。内容如下：348static struct platform_driver s3c24xx_uda134x_driver = 349.probe = s3c24xx_uda134x_probe,350.remove = s3c24xx_uda134x_remove,351.driver = 352.name = s3c24xx_uda134x,353.owner = THIS_MODULE,354,355;由上面的name = s3c24xx_uda134x可知，这个驱动对应的平台设备早在系统启动时在dev_init中注册进来了，所以接下来的事情就是直接调用probe方法。290static int s3c24xx_uda134x_probe(struct platform_device *pdev)291292int ret;293294printk(KERN_INFO S3C24XX_UDA134X SoC Audio drivern);295296s3c24xx_uda134x_l3_pins = pdev-dev.platform_data;297if (s3c24xx_uda134x_l3_pins = NULL) 298printk(KERN_ERR S3C24XX_UDA134X SoC Audio: 299 unable to find platform datan);300return -ENODEV;301302s3c24xx_uda134x.power = s3c24xx_uda134x_l3_pins-power;303s3c24xx_uda134x.model = s3c24xx_uda134x_l3_pins-model;304305if (s3c24xx_uda134x_setup_pin(s3c24xx_uda134x_l3_pins-l3_data,306 data) l3_clk,309 clk) l3_data);311return -EBUSY;312313if (s3c24xx_uda134x_setup_pin(s3c24xx_uda134x_l3_pins-l3_mode,314 mode) l3_data);316gpio_free(s3c24xx_uda134x_l3_pins-l3_clk);317return -EBUSY;318319320s3c24xx_uda134x_snd_device = platform_device_alloc(soc-audio, -1);321if (!s3c24xx_uda134x_snd_device) 322printk(KERN_ERR S3C24XX_UDA134X SoC Audio: 323 Unable to registern);324return -ENOMEM;325326327platform_set_drvdata(s3c24xx_uda134x_snd_device,328 &s3c24xx_uda134x_snd_devdata);329s3c24xx_uda134x_snd_devdata.dev = &s3c24xx_uda134x_snd_device-dev;330ret = platform_device_add(s3c24xx_uda134x_snd_device);331if (ret) 332printk(KERN_ERR S3C24XX_UDA134X SoC Audio: Unable to addn);333platform_device_put(s3c24xx_uda134x_snd_device);334335336return ret;337305-318行就是设置udal34x要用的gpio引脚的功能。320-334行是融入soc-core的关键，320行申请的platform_dev是soc-core的device结构。对应驱动的名称也应该是soc-audio。330行是问题的关键，s3c24xx_uda134x_snd_device注册并与soc-core驱动进行匹配。相关的内容在linux/sound/soc/soc-core.c文件中。Soc-core的入口是module_init（snd_soc_init）。2546static int _init snd_soc_init(void)25472548#ifdef CONFIG_DEBUG_FS2549debugfs_root = debugfs_create_dir(asoc, NULL);2550if (IS_ERR(debugfs_root) | !debugfs_root) 2551printk(KERN_WARNING2552 ASoC: Failed to create debugfs directoryn);2553debugfs_root = NULL;25542555#endif25562557return platform_driver_register(&soc_driver);25582557行是soc-core驱动注册的核心，soc_driver的内容如下：1057/* ASoC platform driver */1058static struct platform_driver soc_driver = 1059.driver= 1060.name= soc-audio,1061.owner= THIS_MODULE,1062.pm= &soc_pm_ops,1063,1064.probe= soc_probe,1065.remove= soc_remove,1066;Soc_driver和s3c24xx_uda134x_snd_device的名称匹配，满足mach的基本条件。后面会调用soc_driver的probe方法进行驱动的进一步枚举。978/* probes a new socdev */979static int soc_probe(struct platform_device *pdev)980981int ret = 0;982struct snd_soc_device *socdev = platform_get_drvdata(pdev);983struct snd_soc_card *card = socdev-card;984985/* Bodge while we push things out of socdev */986card-socdev = socdev;987988/* Bodge while we unpick instantiation */989card-dev = &pdev-dev;990ret = snd_soc_register_card(card);991if (ret != 0) 992dev_err(&pdev-dev, Failed to register cardn);993return ret;994995996return 0;997928行是获取平台驱动数据，这里就是前面设置的：platform_set_drvdata(s3c24xx_uda134x_snd_device,&s3c24xx_uda134x_snd_devdata);s3c24xx_uda134x_snd_devdata的数据类型为struct snd_soc_devicestatic struct snd_soc_device s3c24xx_uda134x_snd_devdata = .card = &snd_soc_s3c24xx_uda134x,.codec_dev = &soc_codec_dev_uda134x,.codec_data = &s3c24xx_uda134x,;Struct snd_soc_device描述了一个soc子系统中的soc设备其成员如下：struct snd_soc_device struct device *dev;struct snd_soc_card *card;struct snd_soc_codec_device *codec_dev;void *codec_data;首先主要关注struct snd_soc_card *card;这个数据结构，后面的内容就是这张声卡实例化。475struct snd_soc_card 476char *name;477struct device *dev;478479struct list_head list;480481int instantiated;482483int (*probe)(struct platform_device *pdev);484int (*remove)(struct platform_device *pdev);485486/* the pre and post PM functions are used to do any PM work before and487 * after the codec and DAIs do any PM work. */488int (*suspend_pre)(struct platform_device *pdev, pm_message_t state);489int (*suspend_post)(struct platform_device *pdev, pm_message_t state);490int (*resume_pre)(struct platform_device *pdev);491int (*resume_post)(struct platform_device *pdev);492493/* callbacks */494int (*set_bias_level)(struct snd_soc_card *,495496497/* CPU Codec DAI links */498struct snd_soc_dai_link *dai_link;499int num_links;500501struct snd_soc_device *socdev;502503struct snd_soc_codec *codec;504505struct snd_soc_platform *platform;506struct delayed_work delayed_work;507struct work_struct deferred_resume_work;508;接下来进入到snd_soc_register_card(card);函数，这事soc_probe的核心。2302static int snd_soc_register_card(struct snd_soc_card *card)23032304if (!card-name | !card-dev)2305return -EINVAL;23062307INIT_LIST_HEAD(&card-list);2308card-instantiated = 0;23092310mutex_lock(&client_mutex);2311list_add(&card-list, &card_list);2312snd_soc_instantiate_cards();2313mutex_unlock(&client_mutex);23142315dev_dbg(card-dev, Registered card %sn, card-name);23162317return 0;2318函数首先初始化一个list头，并将当前card加入到card_list全局的一张soc声卡链表中。然后就调用snd_soc_instantiate_cards();来具体实例化一张声卡。971static void snd_soc_instantiate_cards(void)972973struct snd_soc_card *card;974list_for_each_entry(card, &card_list, list)975snd_soc_instantiate_card(card);976974行遍历card_list然后调用snd_soc_instantiate_card实例化。840static void snd_soc_instantiate_card(struct snd_soc_card *card)841842struct platform_device *pdev = container_of(card-dev,843 struct platform_device,844 dev);845struct snd_soc_codec_device *codec_dev = card-socdev-codec_dev;846struct snd_soc_platform *platform;847struct snd_soc_dai *dai;848int i, found, ret, ac97;849850if (card-instantiated)851return;852853found = 0;854list_for_each_entry(platform, &platform_list, list)855if (card-platform = platform) 856found = 1;857break;858859if (!found) 860dev_dbg(card-dev, Platform %s not registeredn,861card-platform-name);862return;863864865ac97 = 0;866for (i = 0; i num_links; i+) 867found = 0;868list_for_each_entry(dai, &dai_list, list)869if (card-dai_linki.cpu_dai = dai) 870found = 1;871break;872873if (!found) 874dev_dbg(card-dev, DAI %s not registeredn,875card-dai_linki.cpu_dai-name);876return;877878879if (card-dai_linki.cpu_dai-ac97_control)880ac97 = 1;881882883for (i = 0; i num_links; i+) 884if (!card-dai_linki.codec_dai-ops)885card-dai_linki.codec_dai-ops = &null_dai_ops;886887888/* If we have AC97 in the system then dont wait for the889 * codec. This will need revisiting if we have to handle890 * systems with mixed AC97 and non-AC97 parts. Only check for891 * DAIs currently; we cant do this per link since some AC97892 * codecs have non-AC97 DAIs.893 */894if (!ac97)895for (i = 0; i num_links; i+) 896found = 0;897list_for_each_entry(dai, &dai_list, list)898if (card-dai_linki.codec_dai = dai) 899found = 1;900break;901902if (!found) 903dev_dbg(card-dev, DAI %s not registeredn,904card-dai_linki.codec_dai-name);905return;906907908909/* Note that we do not current check for codec components */910911dev_dbg(card-dev, All components present, instantiatingn);912913/* Found everything, bring it up */914if (card-probe) 915ret = card-probe(pdev);916if (ret 0)917return;918919920for (i = 0; i num_links; i+) 921struct snd_soc_dai *cpu_dai = card-dai_linki.cpu_dai;922if (cpu_dai-probe) 923ret = cpu_dai-probe(pdev, cpu_dai);924if (ret probe) 930ret = codec_dev-probe(pdev);931if (ret probe) 936ret = platform-probe(pdev);937if (ret delayed_work, close_delayed_work);943#ifdef CONFIG_PM944/* deferred resume work */945INIT_WORK(&card-deferred_resume_work, soc_resume_deferred);946#endif947948card-instantiated = 1;949950return;951952platform_err:953if (codec_dev-remove)954codec_dev-remove(pdev);955956cpu_dai_err:957for (i-; i = 0; i-) 958struct snd_soc_dai *cpu_dai = card-dai_linki.cpu_dai;959if (cpu_dai-remove)960cpu_dai-remove(pdev, cpu_dai);961962963if (card-remove)964card-remove(pdev);965850行如果声卡已经是实例化了的就直接返回。854行遍历platform_list链表，这个platform_list是个全局变量初始化是通过linux/sound/soc/s3c24xx/s3c24xx-pcm.c中的初始化完成的，内容如下：static int _init s3c24xx_soc_platform_init(void)return snd_soc_register_platform(&s3c24xx_soc_platform);module_init(s3c24xx_soc_platform_init);snd_soc_register_platform目标是注册一个soc_platform结构到platform_list链表中供后文使用。这里对应得平台是s3c24xx_soc_platform，如下：459struct snd_soc_platform s3c24xx_soc_platform = 460.name= s3c24xx-audio,461.pcm_ops = &s3c24xx_pcm_ops,462.pcm_new= s3c24xx_pcm_new,463.pcm_free= s3c24xx_pcm_free_dma_buffers,464;snd_soc_register_platform完成的工作主要是将s3c24xx_soc_platform加入到platform_list，同时重新扫描card链，看是否有卡兼容当前soc_platform。具体代码如下：2431int snd_soc_register_platform(struct snd_soc_platform *platform)24322433if (!platform-name)2434return -EINVAL;24352436INIT_LIST_HEAD(&platform-list);24372438mutex_lock(&client_mutex);2439list_add(&platform-list, &platform_list);2440snd_soc_instantiate_cards();2441mutex_unlock(&client_mutex);24422443pr_debug(Registered platform %sn, platform-name);24442445return 0;24462440行重新回到了snd_soc_instantiate_cards()中，解释清楚platform_list以后继续会爱到snd_soc_instantiate_cards函数。855行匹配两个平台是否一致。一路走来card-platform实际上就是s3c24xx_uda134x_snd_devdata中的snd_soc_s3c24xx_uda134x指向的platform。static struct snd_soc_device s3c24xx_uda134x_snd_devdata = .card = &snd_soc_s3c24xx_uda134x,.codec_dev = &soc_codec_dev_uda134x,.codec_data = &s3c24xx_uda134x,;static struct snd_soc_card snd_soc_s3c24xx_uda134x = .name = S3C24XX_UDA134X,.platform = &s3c24xx_soc_platform,.dai_link = &s3c24xx_uda134x_dai_link,.num_links = 1,;从上面的结构不难看出card-platform=&s3c24xx_soc_platform，与之前注册的一至，found=1，跳出搜索，反之如果没有找到匹配的目标，表示platform还尚未注册进来，一直等到platform注册再次调用instantial_card来实现平台的匹配。找完platform，接下来进入数字音频接口的匹配也就是dai（digital audio interface），整个dai匹配的过程与platform的匹配过程相似的，dai_list注册的内容如下：/linux/sound/soc/s3c24xx/s3c24xx-i2s.cstatic int _init s3c24xx_i2s_init(void)return snd_soc_register_dai(&s3c24xx_i2s_dai);module_init(s3c24xx_i2s_init);snd_soc_register_dai注册数字接口的内容如下：2345int snd_soc_register_dai(struct snd_soc_dai *dai)23462347if (!dai-name)2348return -EINVAL;23492350/* The device should become mandatory over time */2351if (!dai-dev)2352printk(KERN_WARNING No device for DAI %sn, dai-name);23532354if (!dai-ops)2355dai-ops = &null_dai_ops;23562357INIT_LIST_HEAD(&dai-list);23582359mutex_lock(&client_mutex);2360list_add(&dai-list, &dai_list);2361snd_soc_instantiate_cards();2362mutex_unlock(&client_mutex);23632364pr_debug(Registered DAI %sn, dai-name);23652366return 0;23672354-2355行是如果dai没有注册操作方法，那么就使用默认的dai设置方法。这里注册的dai接口内容如下：struct snd_soc_dai s3c24xx_i2s_dai = .name = s3c24xx-i2s,.id = 0,.probe = s3c24xx_i2s_probe,.suspend = s3c24xx_i2s_suspend,.resume = s3c24xx_i2s_resume,.playback = .channels_min = 2,.channels_max = 2,.rates = S3C24XX_I2S_RATES,.formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,.capture = .channels_min = 2,.channels_max = 2,.rates = S3C24XX_I2S_RATES,.formats = SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE,.ops = &s3c24xx_i2s_dai_ops,;和snd_soc_register_platform一样，snd_soc_register_dai同样调用了snd_soc_instantiate_cards()来重新实例化card。另外需要注意的是struct snd_soc_card结构中的struct snd_soc_dai_link实际上关联链接的是cpu音频接口与codec编解码接口。内容如下：struct snd_soc_dai_link char *name;/* Codec name */char *stream_name;/* Stream name */* DAI */struct snd_soc_dai *codec_dai;struct snd_soc_dai *cpu_dai;/* machine stream operations */struct snd_soc_ops *ops;/* codec/machine specific init - e.g. add machine controls */int (*init)(struct snd_soc_codec *codec);/* Symmetry requirements */unsigned int symmetric_rates:1;/* Symmetry data - only valid if symmetry is being enforced */unsigned int rate;/* DAI pcm */struct snd_pcm *pcm;很明显struct snd_soc_dai *codec_dai;和struct snd_soc_dai *cpu_dai;分别指向了不同的音频接口，这里card-dai_linki.cpu_dai= &s3c24xx_i2s_dai指的是cpu的i2s接口，与刚注册的相同。所以接口匹配，注意snd_soc_instantiate_card中879行是关于AC97声卡的配置，这里略过。883-886行是关于数字编解码接口的相关信息，card-dai_linki.codec_dai-ops内容如下：static struct snd_soc_dai_link s3c24xx_uda134x_dai_link = .name = UDA134X,.stream_name = UDA134X,.codec_dai = &uda134x_dai,.cpu_dai = &s3c24xx_i2s_dai,.ops = &s3c24xx_uda134x_ops,;struct snd_soc_dai uda134x_dai = .name = UDA134X,/* playback capabilities */.playback = .stream_name = Playback,.channels_min = 1,.channels_max = 2,.rates = UDA134X_RATES,.formats = UDA134X_FORMATS,/* capture capabilities */.capture = .stream_name = Capture,.channels_min = 1,.channels_max = 2,.rates = UDA134X_RATES,.formats = UDA134X_FORMATS,/* pcm operations */.ops = &uda134x_dai_ops,;894-907行是不支持AC97标准的的codec相关的处理，这里还是使用了dai_list链表。Codec的注册在/sound/soc/codecs/uda134x.c中的module_init(uda134x_init);static int _init uda134x_init(void)return snd_soc_register_dai(&uda134x_dai);codec_dai的内容如下:struct snd_soc_dai uda134x_dai = .name = UDA134X,/* playback capabilities */.playback = .stream_name = Playback,.channels_min = 1,.channels_max = 2,.rates = UDA134X_RATES,.formats = UDA134X_FORMATS,/* capture capabilities */.capture = .stream_name = Capture,.channels_min = 1,.channels_max = 2,.rates = UDA134X_RATES,.formats = UDA134X_FORMATS,/* pcm operations */.ops = &uda134x_dai_ops,;911行开始，是真正instantiating的过程，下面一一分析：914行如果card有probe方法，则直接调用。这里没有提供也就跳过了。920-927行是cpu_dai接口的枚举过程，对应的函数在linux/sound/soc/s3c24xx/s3c24xx-i2s.c中的s2c24xx_i2s_probe，内容如下：389static int s3c24xx_i2s_probe(struct platform_device *pdev,390 struct snd_soc_dai *dai)391392pr_debug(Entered %sn, _func_);393394s3c24xx_i2s.regs = ioremap(S3C2410_PA_IIS, 0x100);395if (s3c24xx_i2s.regs = NULL)396return -ENXIO;397398s3c24xx_i2s.iis_clk = clk_get(&pdev-dev, iis);399if (s3c24xx_i2s.iis_clk = NULL) 400pr_err(failed to get iis_clockn);401iounmap(s3c24xx_i2s.regs);402return -ENODEV;403404clk_enable(s3c24xx_i2s.iis_clk);405406/* Configure the I2S pins in correct mode */407s3c2410_gpio_cfgpin(S3C2410_GPE0, S3C2410_GPE0_I2SLRCK);408s3c2410_gpio_cfgpin(S3C2410_GPE1, S3C2410_GPE1_I2SSCLK);409s3c2410_gpio_cfgpin(S3C2410_GPE2, S3C2410_GPE2_CDCLK);410s3c2410_gpio_cfgpin(S3C2410_GPE3, S3C2410_GPE3_I2SSDI);411s3c2410_gpio_cfgpin(S3C2410_GPE4, S3C2410_GPE4_I2SSDO);412413writel(S3C2410_IISCON_IISEN, s3c24xx_i2s.regs + S3C2410_IISCON);414415s3c24xx_snd_txctrl(0);416s3c24xx_snd_rxctrl(0);417418return 0;419这个函数主要是针对s3c2440 I2S内部寄存器的配置。394行重映射内部寄存器，398-404行是设置系统时钟。407-412行是设置I2S的GPIO功能，使之支持I2S413行使能I2S功能415行函数实现如下：76static void s3c24xx_snd_txctrl(int on)7778u32 iisfcon;79u32 iiscon;80u32 iismod;8182pr_debug(Entered %sn, _func_);8384iisfcon = readl(s3c24xx_i2s