[alsa-devel] Kernel Device Tree entries for simple-audio-card

[Caleb Crome]

On Mon, Sep 28, 2015 at 5:08 PM, Rick Mann <rmann at latencyzero.com> wrote:

>
> > On Sep 28, 2015, at 16:46 , Caleb Crome <caleb at crome.org> wrote:
> >
> > Hmm, the pinmux looks right, except that you have your TX set as an
> input.  You should have this:
> >
> > mymcasp1_pins_default: mymcasp1_pins_default {
> >       pinctrl-single,pins = <
> >               0x1ac ( PIN_OUTPUT | MUX_MODE0 ) /* (A14)
> mcasp0_ahclkx.mcasp0_ahclkx */
> >               0x190 ( PIN_INPUT | MUX_MODE0 ) /* (A13)
> mcasp0_aclkx.mcasp0_aclkx */
> >               0x194 ( PIN_INPUT | MUX_MODE0 ) /* (B13)
> mcasp0_fsx.mcasp0_fsx */
> >               0x198 ( PIN_INPUT | MUX_MODE0 ) /* (D12)
> mcasp0_axr0.mcasp0_axr0 */
> >               0x19c ( PIN_OUTPUT | MUX_MODE2 ) /* (C12)
> mcasp0_ahclkr.mcasp0_axr2 */
> >       >;
> > };
>
> The DTBO for the Audio Cape didn't mark the TX as an output, but I surely
> can try that.
>

That's because you didn't tell it to :-)  There's checkbox you need to
uncheck to make it  Tx.  It's an uncelar UI.  You uncheck Rx to make it a
Tx.


That won't get your clocking going unfortunately.

Also, the DTBO I found for the audio cape is for the BeagleBone, not the
BeagleBoneBlack, so that threw me for a while.

also, I got things running using the audio cape and the davinci-evm.c
device tree entry, not the simple-audio-card.  I ended up putting a lot of
printk's into the kernel so I could trace out how the whole thing worked.

Your fundamental problem seems to be in getting the McASP's output clock
going.  Once that's going, then you can worry about getting the codec's PLL
to output BCLK and WCLK.

Look through the davinci-evm.c and see what it does that simple-audio-card
doesn't.  It's something to do with the MCLK for sure.

Once your MCLK is going, you can use i2cdump to look at the codec registers:

sudo i2cdump -f -y 1 0x18

or similar.



-caleb