[alsa-devel] ASoC MPC5xxx PSC AC97 audio driver

[David Jander]

Dear Jon,

On Thu, 8 Sep 2011 06:55:56 -0400
"jonsmirl at gmail.com" <jonsmirl at gmail.com> wrote:

> On Thu, Sep 8, 2011 at 6:45 AM, David Jander <david.jander at protonic.nl>
> wrote:
> >
> > Dear Jon,
> >
> > Thanks for replying so quickly.
> >
> > On Thu, 8 Sep 2011 06:28:02 -0400
> > "jonsmirl at gmail.com" <jonsmirl at gmail.com> wrote:
> >> On Thu, Sep 8, 2011 at 6:16 AM, David Jander <david.jander at protonic.nl>
> >> wrote:
> >> >
> >> > Dear Jon,
> >>
> >> Here's the device tree...
> >> http://git.digispeaker.com/?p=digispeaker-kernel.git;a=blob;f=arch/powerpc/boot/dts/dspeak01.dts;h=50cc247b4da0eb2bc4deb315b1b5348af87e5979;hb=9166a4a4141ab7c8d7a7b97fa5b726e11a8d0ca4
> >
> > Thanks... but it uses I2S, not AC97 :-(
> > It doesn't have a "fsl,mpc5200-pcm" node either, btw.
> > In the case of I2C, this makes some sense, since the Codec is usually
> > connected to two different interfaces at the same time (I2S and I2C for
> > control), so you have 2 device nodes. AC97 OTOH has just one interface. It
> > is connected to a AC97 bus (a PSC in this case). AFAICS there are no OF
> > bindings yet for an AC97 bus, so the actual codec doesn't figure and thus
> > still needs this ugly fabric driver thing.
> 
> Try the pcm030 device tree...
> 
> http://git.digispeaker.com/?p=digispeaker-kernel.git;a=blob;f=arch/powerpc/boot/dts/pcm030.dts;h=30bfdc04c6dfacd88a9c6e325e873d75a633bdf5;hb=HEAD

I had also looked at that one.... still no "fsl,mpc5200-pcm" node. I would not
expect one either, given the way the fabric driver works. But what is the
reason for this OF compatible string then?

Most important question: Does the mpc5200_dma.c/mpc5200_psc_ac97.c combination
in current mainline still work correctly?

I am unable (by inference) to say for sure that mpc5200_hpcd_probe() will
always be called before psc_ac97_of_probe(). If it is not, the latter will
OOPS.
In fact, when I try to mimic the same on a MPC5121e, it does get called in the
opposite order! My theory is that this order may have changed in recent
versions of kernel/ALSA, and that since that moment this driver has been
broken and nobody noticed yet. I need to know, because I intend to enhance
mpc5200_psc_ac97.c, to also support MPC512x, but this is not working the way it
is written now. If I knew for sure that mpc5200 still works this way, I would
need to find a bug in my code. In the other case, I'd just go and fix the
driver for MPC5200 also, but I have no hardware to try it out myself.

Best regards,

-- 
David Jander
Protonic Holland.