[alsa-devel] simple-audio-card with omap4-dmic

[Jack Mitchell]

On 03/06/15 16:37, Jack Mitchell wrote:
> I'm currently working with a PandaBoard clone (OMAP44xx) which doesn't 
> have the usual twl6040 codec, however I would like to attach a digital 
> microphone directly into the OMAP.
>
> I have added the following to my device tree:
>
>         sound {
>                 compatible = "simple-audio-card";
>                 simple-audio-card,name = "dmic-card";
>
>                 simple-audio-card,format = "pdm";
>
>                 status = "okay";
>
>                 simple-audio-card,dai-link at 0 {
>                         cpu {
>                                 sound-dai = <&dmic>;
>                         };
>
>                         codec {
>                                 sound-dai = <&dmic_codec>;
>                         };
>                 };
>         };
>
>         dmic_codec: dmic_codec {
>                 #sound-dai-cells = <0>;
>                 compatible = "linux,dmic-codec";
>         };
>
> and created a small patch to allow the generic dmic-hifi codec to be 
> instantiated from device tree.
>
> diff --git a/sound/soc/codecs/dmic.c b/sound/soc/codecs/dmic.c
> index fde5325..67b9198 100644
> --- a/sound/soc/codecs/dmic.c
> +++ b/sound/soc/codecs/dmic.c
> @@ -69,11 +69,18 @@ static int dmic_dev_remove(struct platform_device 
> *pdev)
>         return 0;
>  }
>
> -MODULE_ALIAS("platform:dmic-codec");
> +#ifdef CONFIG_OF
> +static const struct of_device_id dmic_dt_ids[] = {
> +        { .compatible = "linux,dmic-codec", },
> +        { }
> +};
> +MODULE_DEVICE_TABLE(of, dmic_dt_ids);
> +#endif
>
>  static struct platform_driver dmic_driver = {
>         .driver = {
>                 .name = "dmic-codec",
> +               .of_match_table = of_match_ptr(dmic_dt_ids),
>         },
>         .probe = dmic_dev_probe,
>         .remove = dmic_dev_remove,
> @@ -81,6 +88,7 @@ static struct platform_driver dmic_driver = {
>
>  module_platform_driver(dmic_driver);
>
> +MODULE_ALIAS("platform:dmic-codec");
>  MODULE_DESCRIPTION("Generic DMIC driver");
>  MODULE_AUTHOR("Liam Girdwood <lrg at slimlogic.co.uk>");
>  MODULE_LICENSE("GPL");
>
> However, no soundcards get loaded, and I don't get error or warnings 
> in dmesg, so I'm at a bit of a loss at where I'm going wrong. Can 
> anybody see any glaring mistakes? I know the driver is definitely 
> getting loaded as I have seen errors relating to me not specifying the 
> sound-dai-cells from the simple-audio-card driver.
>
> Any ideas would be greatly recieved!
>
> Cheers,
>
>
Ok, playing with this a bit more and I find if I manually modprobe 
snd-soc-dmic then it fires into life. There are other problems with 
capturing but I'll fight those myself for a bit first.