[Gta04-owner] fm-tuner - was Re: hw routing audio patch removed in 3.7?

[Andreas Kemnade]

On Mon, 2013-06-24 at 11:38 +0200, Dr. H. Nikolaus Schaller wrote: 
> Hi,
> fm-radio appears to work. At least on one board (the one where I did solder some wires to measure the clocks and PCM signals).
> [...] 
> Now comes the bad news: it works only on one GTA04 board and I don't
> know why it fails on the others I have tested. Since they have no wires I
> can't check if the clocks are available and the Si47xx is sending PCM
> to the CPU or not. Or if there is something unreliable in the McBSP config.
> 
> It could also be some hardware issue. If you look into the schematics, there
> are series resistors for the McBSP1 interface. Their values are choosen
> based on the recommendations of a reference design we had found.
> 
> But 2k2 appears a little high value, taking into account that we have a 2.5 MHz
> clock. I.e. the signals may be damped and too slow so that e.g. the clocks
> are not recognized correctly.
> 
I do not understand the connection here. The McBSP sends out its clocks.
It should look at the data pin at the right times and interpret whatever
is avilable there at sampling time if i understand the I2S stuff
correctly. So we should be able to read some suff and arecord should
spit out something.

I just tested a recent 3.7-nplus kernel here and still the old result,
arecord does not get data. I should check uboot. 
> 2. find out why it works on one board only
> 
> e.g. by replacing the series resistors by 50 Ohm. Or doing scope
> measurements.
> 
What about wiring the data input pin to ground? So we can separate the
problem in two things here.
in 
1) make McBSP1 a low-rate replacement for /dev/zero,
   so that arecord spits out lots of zero bytes in a well-controlled
rate.
2) after reconnecting DR to the SI4721, check whether the data is sane.

BTW: Do you have register dumps for the working and the non-working
boards of the McBSP registers?

Last time I did some scope measurements i broke my gps antenna connector
so I am a bit shy now so I hesitate to repeat my scope measurements.

Greetings
Andreas Kemnade