Re: [RFC] Add dB scale information to AK4xxx codec

[Takashi Iwai <tiwai@suse.de>]

At Mon, 4 Sep 2006 12:13:06 +0100,
Jochen Voß wrote:
> 
> Hi Takashi,
> 
> On Mon, Sep 04, 2006 at 11:58:57AM +0200, Takashi Iwai wrote:
> > > From table 17 (page 35) of the AK5365 specs I think that IPGA and DATT
> > > are only separate units inside the chip, but should be treated as one
> > > continuous scale for the purpose of the driver.  The table looks like
> > > the input volume can be adjusted in steps from "mute" to +12dB.  Why
> > > would we want two controls here?
> > 
> > Actually they are treated independently in the chip.  IPGA works like
> > a preamp, and the total volume is IPGA + DATT.  Even if you set a
> > value to IPGA with MSB, say 0x82, DATT won't be changed and the old
> > value is kept.  And it's vice versa - if you set 0x02 later, IPGA will
> > stay as 0x82.  This is so, at least with AK4524 and AK4528.  Possibly
> > this was changed on AK5365, though...
> Did you have a look at table 17?  I think the old behaviour was better.

Yes, the exactly same table appears in AK4524 datasheet, too.
The only question is whether they really behave _indenpendently_.

On AK4524, IPGA and IATT are actually two different values.  As I
wrote, 0x82 only changes IPGA value but doesn't change IATT.  0x02
changes only IATT but not IPGA.  And the total volume is IPGA + IATT.


Takashi

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