MPC5200B AC97 support for recent kernel

MPC5200B AC97 support for recent kernel

[Juergen Beisert]

Hi,

I'm using a 2.6.23 kernel and trying to get the AC97 running on my MPC5200B=
=20
based CPU card. I'm using a patch stack posted here last year. FEC and ATA=
=20
seems running correctly. Also the AC97 seems to run, but I can hear some=20
noise only. But ALSA does detect the external Wolfson codec and its=20
capabilities correctly, so I think the AC97 link works as expected.

Some things I noticed:

 - I can control the volume of the noise with alsamixer
 - the external codes outputs the correct clock (~12 MHz)
 - the MPC5200B AC97 driver receives interrupts from the bestcomm unit (to
   report progress to the pcm framework)
 - everything seems ways too fast. A four minutes mp3 song is ready after
   40 seconds
 - I'm not sure: What type of data wants the AC97 PCS unit? AC97
   data slots are 20 bits wide. int32_t or 24 bits per sample? Big endian?
 - does it use interleave? Left, right, left, right, ... to be fed into AC97
   data slot 3 and 4?

Any ideas?

Juergen

=2D-=20
Dipl.-Ing. Juergen Beisert | http://www.pengutronix.de
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