[alsa-devel] [PATCH] ASoC: ssm2602: Fix ADC powerup sequencing

[Philipp Zabel]

On Fri, 2018-05-25 at 15:52 +0100, Mark Brown wrote:
> On Fri, May 25, 2018 at 01:42:53PM +0200, Marco Felsch wrote:
> 
> > Also the formula for the delay time (t = C × 25,000/3.5) depends only on
> > the capacity size.
> 
> Why not just have the user specify the capacitance of the capacitor on
> the rail which they can directly read from the schematic rather than
> forcing them to do the calcualtion?  That seems a bit clearer and more
> user friendly (plus if someone decides the spec was wrong it's easier to
> roll out fixes).

The exact capacitance may not be known or vary above the nominal value
because of cheap components, and the formula from the datasheet is just
a guideline.

I'd expect the usual method to set this delay to be semi-empirical:
"start from the value calculated from datasheet and schematics and then
increase until no more audio artifacts on a representative sample of
boards".
I think it is be better to specify a delay that works than a bogus
capacitance value that happens to correspond to a delay that works.

regards
Philipp