ALSA(4) --- CPU DAI实践

CPU_DAI实践

物理拓扑图

在这里插入图片描述

上图可知，从dma过来数据，会保存在DAI的一个FIFO队列中，数据是并行过来的各个通道数据，经过shift移位寄存器，再经过P2S并行转串行，再经过DAVC音量控制输出到GPIO端口

音频数据接口实践

snd_soc_dai_driver

static struct snd_soc_dai_driver tcc_i2s_dai_drv[DAI_BLOCK_TYPE_MAX] = {
        [DAI_BLOCK_STEREO_TYPE] = {
                .name = "tcc-i2s",
                .suspend = tcc_i2s_dai_suspend,
                .resume = tcc_i2s_dai_resume,
                .playback = {
                        .stream_name = "I2S-Playback",
                        .channels_min = 1,
                        .channels_max = 32,
                        .rates = SNDRV_PCM_RATE_8000_192000,
                        .formats =
                                (SNDRV_PCM_FMTBIT_S16_LE
                                |SNDRV_PCM_FMTBIT_S24_LE),
                },
                .capture = ...
                .ops = &tcc_i2s_ops
                ....
        }
}

dai_driver都会注册到ALSA Core内部上去，最后通过调用其ops函数操作集来访问cpu_dai模块

snd_soc_dai_driver的ops函数集

static struct snd_soc_dai_ops tcc_i2s_ops = {
        .set_clkdiv     = tcc_i2s_set_clkdiv,
        .set_bclk_ratio = tcc_i2s_set_bclk_ratio, //以上2个是传统的i2s同学参数，mclk和bclk的分频参数
        .set_fmt        = tcc_i2s_set_dai_fmt,
        ....