[alsa-devel] Support two wm8962 codec in i.mx6 board.

[Nicolin Chen]

On Tue, Mar 17, 2015 at 09:51:22AM +0800, Shawn Embedded wrote:

>    Actually I donot know much about dai-link. I just got started
> recently to working on this requirement.
>    You mean to create the same platform device as the now-working one
> in board-xxx.c. Sure I can do that.

Are you using old kernel version that's not included Device Tree yet?

If so, yes, you need to add a similar platform device as the original
one but you need to assign a different AUDMUX port.

>    Since the two wm8962 codecs are on different I2C buses, so I just
> need to update the corresponding i2c's i2c_board_info structure to
> support the second one as a I2C device?

Exactly.

> > Supposing two WM8962 chips on one board, there should be two WM8962
> > nodes hanging to the I2C node with different I2C slave addresses.
> 
>   Yes, but the I2C slave addresses should be the same, IIRC, only on
> different I2C buses.

No problem for this. You can use same slave address but connecting to
different I2C buses. As long as you system probes two different CODECs,
that's fine.

>   What do you mean by "two wm8962 nodes" ?

If you are not using code from Linux Mainline, just forget about it.

>   In my experience, the corresponding files are board-xxx.c,
> imx-wm8962.c, wm8962.c.
> 
>   I looked at the wm8962.c, which is the codec driver file, very independent.
>   There comes the wm8962_i2c_probe() and wm8962_probe().
>   In wm8962_i2c_probe(), snd_soc_register_codec() is called, so a new
> codec structure will be created when there comes another i2c device
> named "wm8962".
>   Seems no need to change anything in wm8962.c, if the external
> hardware signals of the second wm8962 are connected in the same way as
> the first now-working one, right?

No, you don't need to. Just register it in the board level driver.

>   Do you think any changes should be made to imx-wm8962.c which is the
> machine driver file for wm8962 on imx6?

Ideally, You only need to append a new platform device in the board
level driver, same as you do for WM8962 CODECs.

> static struct snd_soc_dai_link imx_dai[] = {
> {
> .name = "HiFi",
> .stream_name = "HiFi",
> .codec_dai_name = "wm8962",
> .codec_name = "wm8962.0-001a",
> .cpu_dai_name = "imx-ssi.1",
> .platform_name = "imx-pcm-audio.1",
> .init = imx_wm8962_init,
> .ops = &imx_hifi_ops,
> },
> };

Okay...this one looks like you are using an old version BSP, other
than the code from Linux Mainline.

> in imx-wm8962.c, should I copy them to create a new copy of them
> respectively? Or no need to do this?

In this case, yes, because the structure has hard code. Otherwise,
you new dai-link will not be successfully connected.

> In board-xxx.c, do I just need to copy declarations related to wm8962?
> Is that enough?

I think so.

>   Again, could you tell me how to make two different dai-link nodes?
>   Sorry for knowing not much about this.

That's for Device Tree which you are not using.

Nicolin