linux-kernel - Re: [PATCH] ASoC: wm_hubs: Fix DC Servo readback

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Message-ID: <20140813110844.GF15833@opensource.wolfsonmicro.com>
Date:	Wed, 13 Aug 2014 12:08:44 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Nikesh Oswal <nikesh@...nsource.wolfsonmicro.com>
Cc:	broonie@...nel.org, lgirdwood@...il.com, tiwai@...e.de,
	alsa-devel@...a-project.org, patches@...nsource.wolfsonmicro.com,
	linux-kernel@...r.kernel.org, perex@...ex.cz
Subject: Re: [PATCH] ASoC: wm_hubs: Fix DC Servo readback

On Wed, Aug 13, 2014 at 11:47:20AM +0100, Nikesh Oswal wrote:
> wm_hubs is a common driver code shared by WM8958, WM1811, WM8944
> and WM8993 all these codecs have the DC Servo Values either in register
> 57h or 59h. Current code was reading register 58h for WM8958 and WM8994
> revisions 2 and 3 but looking at the data sheet the DC Servo Values are
> stored in register 57h for these codecs. This patch fixes it by reading
> the correct register for DC Servo
> 
> Signed-off-by: Nikesh Oswal <nikesh@...nsource.wolfsonmicro.com>
> ---
>  sound/soc/codecs/wm_hubs.c |    3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm_hubs.c b/sound/soc/codecs/wm_hubs.c
> index 916817f..95c5d71 100644
> --- a/sound/soc/codecs/wm_hubs.c
> +++ b/sound/soc/codecs/wm_hubs.c
> @@ -210,9 +210,6 @@ static int wm_hubs_read_dc_servo(struct snd_soc_codec *codec,
>  	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.

Thanks,
Charles
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