24-S3C6410+WM9714 ASoC驱动实例
17.6 S3C6410+WM9714 ASoC驱动实例
LDD6410开发板上为S3C6410的AC'97接口上连接了Wolfson公司的WM9714 Codec芯片，其硬件连接如图17.6所示。WM9714芯片主要外接了Microphone、Line in模拟输入和Headphone模拟输出。而在数字接口方面，与S3C6410 CPU的连接包含了AC-Link总线上必要的信号。
WM9714是一款比较复杂的Codec芯片，其与AC'97 2.2兼容。内部集成了HiFi立体声ADC/DAC、AUX ADC/DAC和用于话音的Voice ADC/DAC，同时包含数个mux和mixer以及增益调节，在使用该芯片上，读懂数据手册中的“Audio Paths Overview”即音频路径图非常关键。
LDD6410开发板上ASoC驱动的3部分分别是。
（1）Codec驱动。由内核源代码sound/soc/codecs/wm9713.c实现。
（2）平台驱动。由内核源代码sound/soc/s3c/s3c-ac97.c实现S3C6410 CPU端的DAI驱动，由sound/soc/s3c/s3c-pcm.c实现CPU端的DMA驱动。
（3）板驱动。由内核源代码sound/soc/s3c/smdk6410_wm9713.c实现，它将第1部分和第2部分进行绑定。
sound/soc/codecs/wm9713.c超过1300行，支持WM9713、WM9714，主要定义了一系列的mixer控制、DAPM、AC97底层读写、时钟/PLL控制以及snd_soc_ops的成员函数。我们不可能一一列举，这里仅抽取其核心一观，如代码清单17.35。
代码清单17.35 WM9713/4的ASoC Codec驱动
1 / 一系列的mixer控制 /
2 static const struct soc_enum wm9713_enum[] = {
3 SOC_ENUM_SINGLE(AC97_LINE, 3, 4, wm9713_mic_mixer), / record mic mixer 0 /
4 ...
5 };
6
7 static const struct snd_kcontrol_new wm9713_snd_ac97_controls[] = {
8 SOC_DOUBLE("Speaker Playback Volume", AC97_MASTER, 8, 0, 31, 1),
9 ...
10 };
11
12 / add non dapm controls /
13 static int wm9713_add_controls(struct snd_soc_codec *codec)
14 {
15 int err, i;
16
17 for (i = 0; i < ARRAY_SIZE(wm9713_snd_ac97_controls); i++) {
18 err = snd_ctl_add(codec->card,
19 snd_soc_cnew(&wm9713_snd_ac97_controls[i],
20 codec, NULL));
21 if (err < 0)
22 return err;
23 }
24 return 0;
25 }
26
27 ...
28 static const struct snd_kcontrol_new wm9713_hpl_mixer_controls[] = {
29 ...
30 };
31
32 / Right Headphone Mixers /
33 static const struct snd_kcontrol_new wm9713_hpr_mixer_controls[] = {
34 ...
35 };
36
37 / 一系列的dapm控制 /
38 static const struct snd_soc_dapm_widget wm9713_dapm_widgets[] = {
39 SND_SOC_DAPM_MUX("Capture Headphone Mux", SND_SOC_NOPM, 0, 0,
40 &wm9713_hp_rec_mux_controls),
41 ...
42 };
43
44 static const struct snd_soc_dapm_route audio_map[] = {
45 / left HP mixer /
46 {"Left HP Mixer", "PC Beep Playback Switch", "PCBEEP"},
47 ...
48 };
49
50 static int wm9713_add_widgets(struct snd_soc_codec *codec)
51 {
52 snd_soc_dapm_new_controls(codec, wm9713_dapm_widgets,
53 ARRAY_SIZE(wm9713_dapm_widgets));
54
55 snd_soc_dapm_add_routes(codec, audio_map, ARRAY_SIZE(audio_map));
56
57 snd_soc_dapm_new_widgets(codec);
58 return 0;
59 }
60
61 / io、时钟、格式等的操作 /
62 static unsigned int ac97_read(struct snd_soc_codec *codec,
63 unsigned int reg)
64 {
65 ...
66 }
67
68 static int ac97_write(struct snd_soc_codec *codec, unsigned int reg,
69 unsigned int val)
70 {
71 ...
72 }
73
74 static int wm9713_set_dai_pll(struct snd_soc_dai *codec_dai,
75 int pll_id, unsigned int freq_in, unsigned int freq_out)
76 {
77 ...
78 }
79
80 static int wm9713_set_dai_fmt(struct snd_soc_dai *codec_dai,
81 unsigned int fmt)
82 {
83 ...
84 }
85
86 / 关于音频流的操作snd_soc_ops /
87 static int wm9713_pcm_hw_params(struct snd_pcm_substream *substream,
88 struct snd_pcm_hw_params *params)
89 {
90 ...
91 }
92
93 static void wm9713_voiceshutdown(struct snd_pcm_substream *substream)
94 {
95 ...
96 }
97
98 static int ac97_hifi_prepare(struct snd_pcm_substream *substream)
99 {
100 ...
101 }
102
103 static int ac97_aux_prepare(struct snd_pcm_substream *substream)
104 {
105 ...
106 }
107
108 / DAI /
109 struct snd soc dai wm9713_ dai[] = {
110 {
111 .name = "AC97 HiFi",
112 .type = SND_SOC_DAI_AC97_BUS,
113 .playback = {
114 .stream_name = "HiFi Playback",
115 .channels_min = 1,
116 .channels_max = 2,
117 .rates = WM9713_RATES,
118 .formats = SNDRV_PCM_FMTBIT_S16_LE,},
119 .capture = {
120 .stream_name = "HiFi Capture",
121 .channels_min = 1,
122 .channels_max = 2,
123 .rates = WM9713_RATES,
124 .formats = SNDRV_PCM_FMTBIT_S16_LE,},
125 .ops = {
126 .prepare = ac97_hifi_prepare,},
127 .dai_ops = {
128 .set_clkdiv = wm9713_set_dai_clkdiv,
129 .set_pll = wm9713_set_dai_pll,},
130 },
131 {
132 .name = "AC97 Aux",
133 .playback = {
134 .stream_name = "Aux Playback",
135 .channels_min = 1,
136 .channels_max = 1,
137 .rates = WM9713_RATES,
138 .formats = SNDRV_PCM_FMTBIT_S16_LE,},
139 .ops = {
140 .prepare = ac97_aux_prepare,},
141 .dai_ops = {
142 .set_clkdiv = wm9713_set_dai_clkdiv,
143 .set_pll = wm9713_set_dai_pll,},
144 },
145 {
146 .name = "WM9713 Voice",
147 ...
148 },
149 };
150 EXPORT SYMBOL GPL(wm9713_ dai);
151
152 / snd_soc_codec_device成员 /
153 static int wm9713_soc_suspend(struct platform_device *pdev,
154 pm_message_t state)
155 {
156 ...
157 }
158
159 static int wm9713_soc_resume(struct platform_device *pdev)
160 {
161 ...
162 }
163
164 static int wm9713_soc_probe(struct platform_device *pdev)
165 {
166 struct snd_soc_device *socdev = platform_get_drvdata(pdev);
167 struct snd_soc_codec *codec;
168 int ret = 0, reg;
169
170 ...
171 codec->name = "WM9713";
172 codec->owner = THIS_MODULE;
173 codec->dai = wm9713_dai;
174 codec->num_dai = ARRAY_SIZE(wm9713_dai);
175 codec->write = ac97_write;
176 codec->read = ac97_read;
177 codec->set_bias_level = wm9713_set_bias_level;
178 INIT_LIST_HEAD(&codec->dapm_widgets);
179 INIT_LIST_HEAD(&codec->dapm_paths);
180
181 ret = snd_soc_new_ac97_codec(codec, &soc_ac97_ops, 0);
182 if (ret < 0)
183 goto codec_err;
184
185 / register pcms /
186 ret = snd_soc_new_pcms(socdev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1);
187 if (ret < 0)
188 goto pcm_err;
189
190 ...
191
192 wm9713_add_controls(codec);
193 wm9713_add_widgets(codec);
194 ret = snd_soc_register_card(socdev);
195 ...
196 }
197
198 static int wm9713_soc_remove(struct platform_device *pdev)
199 {
200 ...
201 snd_soc_dapm_free(socdev);
202 snd_soc_free_pcms(socdev);
203 snd_soc_free_ac97_codec(codec);
204 ...
205 return 0;
206 }
207
208 struct snd soc codec device soc codec dev wm9713 = {
209 .probe = wm9713_soc_probe,
210 .remove = wm9713_soc_remove,
211 .suspend = wm9713_soc_suspend,
212 .resume = wm9713_soc_resume,
213 };
214 EXPORT SYMBOL GPL(soc codec dev_ wm9713);
sound/soc/s3c/s3c-ac97.c实现CPU端AC97 DAI的驱动，会导出snd_soc_dai结构体的实例s3c_ac97_dai。sound/soc/s3c/s3c-pcm.c实现CPU端的DMA驱动，其核心如代码清单17.36，它也会导出snd_soc_platform结构体的实例s3c24xx_soc_platform。
代码清单17.36 S3C6410平台驱动DMA进行PCM流操作
1 static const struct snd_pcm_hardware s3c24xx_pcm_hardware = {
2 .info = SNDRV_PCM_INFO_INTERLEAVED |
3 SNDRV_PCM_INFO_PAUSE |
4 SNDRV_PCM_INFO_RESUME |
5 SNDRV_PCM_INFO_BLOCK_TRANSFER |
6 SNDRV_PCM_INFO_MMAP |
7 SNDRV_PCM_INFO_MMAP_VALID,
8 .formats = SNDRV_PCM_FMTBIT_S16_LE |
9 SNDRV_PCM_FMTBIT_U16_LE |
10 SNDRV_PCM_FMTBIT_U8 |
11 SNDRV_PCM_FMTBIT_S24_LE |
12 SNDRV_PCM_FMTBIT_S8,
13 .channels_min = 2,
14 .channels_max = 2,
15 .buffer_bytes_max = 128*1024,
16 .period_bytes_min = PAGE_SIZE,
17 .period_bytes_max = PAGE_SIZE*2,
18 .periods_min = 2,
19 .periods_max = 128,
20 .fifo_size = 32,
21 };
22
23 static int s3c24xx_pcm_hw_params(struct snd_pcm_substream *substream,
24 struct snd_pcm_hw_params *params)
25 {
26 ...
27 }
28
29 static int s3c24xx_pcm_hw_free(struct snd_pcm_substream *substream)
30 {
31 ...
32 }
33
34 static int s3c24xx_pcm_prepare(struct snd_pcm_substream *substream)
35 {
36 ...
37 }
38
39 static int s3c24xx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
40 {
41 ...
42 switch (cmd) {
43 case SNDRV_PCM_TRIGGER_RESUME:
44 ...
45 case SNDRV_PCM_TRIGGER_START:
46 case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
47 prtd->state |= ST_RUNNING;
48 s3c2410_dma_ctrl(prtd->params->channel, S3C2410_DMAOP_START);
49 break;
50
51 ...
52 }
53 ...
54 }
55
56 static snd_pcm_uframes_t
57 s3c24xx_pcm_pointer(struct snd_pcm_substream *substream)
58 {
59 ...
60 return bytes_to_frames(substream->runtime, res);
61 }
62
63 static int s3c24xx_pcm_open(struct snd_pcm_substream *substream)
64 {
65 ...
66 return 0;
67 }
68
69 static int s3c24xx_pcm_close(struct snd_pcm_substream *substream)
70 {
71 ...
72 }
73
74 static int s3c24xx_pcm_mmap(struct snd_pcm_substream *substream,
75 struct vm_area_struct *vma)
76 {
77 ...
78 return dma_mmap_writecombine(substream->pcm->card->dev, vma,
79 runtime->dma_area,
80 runtime->dma_addr,
81 runtime->dma_bytes);
82 }
83
84 static struct snd_pcm_ops s3c24xx_pcm_ops = {
85 .open = s3c24xx_pcm_open,
86 .close = s3c24xx_pcm_close,
87 .ioctl = snd_pcm_lib_ioctl,
88 .hw_params = s3c24xx_pcm_hw_params,
89 .hw_free = s3c24xx_pcm_hw_free,
90 .prepare = s3c24xx_pcm_prepare,
91 .trigger = s3c24xx_pcm_trigger,
92 .pointer = s3c24xx_pcm_pointer,
93 .mmap = s3c24xx_pcm_mmap,
94 };
95
96 static int s3c24xx_pcm_preallocate_dma_buffer(struct snd_pcm *pcm, int stream)
97 {
98 ...
99 buf->area = dma_alloc_writecombine(pcm->card->dev, size,
100 &buf->addr, GFP_KERNEL);
101 if (!buf->area)
102 return -ENOMEM;
103 buf->bytes = size;
104 return 0;
105 }
106
107 static void s3c24xx_pcm_free_dma_buffers(struct snd_pcm *pcm)
108 {
109 ...
110 for(stream=SNDRV_PCM_STREAM_PLAYBACK;stream<=SNDRV_PCM_STREAM_CAPTURE;stream++){
111 substream = pcm->streams[stream].substream;
112 if (!substream)
113 continue;
114
115 buf = &substream->dma_buffer;
116 if (!buf->area)
117 continue;
118
119 dma_free_writecombine(pcm->card->dev, buf->bytes,
120 buf->area, buf->addr);
121 buf->area = NULL;
122 buf->addr = 0;
123 }
124 }
125
126 static u64 s3c24xx_pcm_dmamask = DMA_32BIT_MASK;
127
128 static int s3c24xx_pcm_new(struct snd_card *card,
129 struct snd_soc_dai dai, struct snd_pcm pcm)
130 {
131 ...
132
133 if (dai->playback.channels_min) {
134 ret = s3c24xx_pcm_preallocate_dma_buffer(pcm,
135 SNDRV_PCM_STREAM_PLAYBACK);
136 if (ret)
137 goto out;
138 }
139
140 if (dai->capture.channels_min) {
141 ret = s3c24xx_pcm_preallocate_dma_buffer(pcm,
142 SNDRV_PCM_STREAM_CAPTURE);
143 if (ret)
144 goto out;
145 }
146 out:
147 return ret;
148 }
149
150 struct snd soc platform s3c24xx soc platform = {
151 .name = "s3c24xx-audio",
152 .pcm_ops = &s3c24xx_pcm_ops,
153 .pcm_new = s3c24xx_pcm_new,
154 .pcm_free = s3c24xx_pcm_free_dma_buffers,
155 };
156
157 EXPORT SYMBOL GPL(s3c24xx soc platform);
sound/soc/s3c/smdk6410_wm9713.c的形式与代码清单17.33基本相同，它将前述Codec和平台驱动中导出的symbol绑定在一起，并在模块加载函数中注册一个名为“soc-audio”的platform设备。