[alsa-devel] [PATCH] ASoC: wm_hubs: Fix DC Servo readback

[Mark Brown]

On Wed, Aug 13, 2014 at 12:08:44PM +0100, Charles Keepax wrote:
> On Wed, Aug 13, 2014 at 11:47:20AM +0100, Nikesh Oswal wrote:

> >  	case 2:
> >  		dcs_reg = WM8994_DC_SERVO_4E;
> >  		break;
> > -	case 1:
> > -		dcs_reg = WM8994_DC_SERVO_READBACK;
> > -		break;
> >  	default:
> >  		dcs_reg = WM8993_DC_SERVO_3;
> >  		break;

> This doesn't look right, firstly if it is the same register for
> all versions then surely we should change the code that sets
> dcs_readback_mode rather than setting that to different values
> but treating them the same. Although obviously if nothing still
> uses this case we could remove it as well.

> Also I think the situation is more complex for example on version
> 4.4 of the datasheet for wm8994 the WR_VAL fields appear to be in
> register 59h. Which is not consistent with this.

There was a change in the DC servo between revisions of the WM8994 (at
revision E from the look of the code).  This isn't documented in the
datasheets as they only document current silicon.
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