Sound and the TDA998x binding

[Peter Rosin]

On 2018-11-13 18:24, Russell King - ARM Linux wrote:
> On Tue, Nov 13, 2018 at 01:28:40PM +0000, Peter Rosin wrote:
>> Hi!
>>
>> I'm wondering about some programming details regarding the TDA998x
>> driver...
>>
>> The bindings documentation [1] state that one should fill in the
>> desired register content of the AP_ENA register. However, I cannot
>> find any details anywhere about how one determines what is desired.
>> When I look for data sheets on the Internet, all I find is a "short"
>> data sheet, which is far from enlightening. There are hints about
>> a "full" data sheet in the chapter on legal information of the
>> "short" data sheet. Is the "full" data sheet protected by an NDA
>> or something? That's the only reason I can find for it not being
>> available...
>>
>> Maybe someone with such a "full" data sheet at hand can enlighten
>> me on the workings of this AP_ENA register so that I know what it is
>> that I need to fill in? Since it is so difficult to find this info,
>> maybe it should be added to the binding?
> 
> There's various public documents for the TDA998x chips, some of which
> do contain the register programming information - although we don't
> have definitive information for every variant that the driver supports.

I have looked, and not found anything. Do you have any pointer? For what
chip(s) in the family are there register information?

> Even so, that doesn't give us documentation for this register, so we
> have to resort to code received from other sources.
> 
> The AP_ENA register "audio port enable" is one bit per AP signal, from
> the AP0 pin being bit 0, up to the AP7 pin being bit 7.

Thanks! However, in the "short" sheet for the TDA19988 that I have, there
is this table:

AP0                  WS (word select)
AP1   S/PDIF input   I2S-bus channel 0
AP2   S/PDIF input   I2S-bus channel 1
AP3                  I2S-bus channel 2
AP4                  I2S-bus channel 3
ACLK                 SCK (I2S-bus clock)

AP5 through AP7 are nowhere to be found...

Should I assume that ACLK is an alias for AP5, and that the register
content should be 0x23 for I2S on channel 0? Or is ACLK not part of
the AP_ENA register at all, so that 0x03 is more likely to be correct?

Cheers,
Peter