Sound and the TDA998x binding

[Russell King - ARM Linux]

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.
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.

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