linux-kernel - Re: [PATCH v2] mfd: wm8994: declare dc servo register for wm8958 as volatile

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Date:	Thu, 14 Aug 2014 09:37:53 +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 v2] mfd: wm8994: declare dc servo register for wm8958
	as volatile

On Wed, Aug 13, 2014 at 04:27:29PM +0100, Nikesh Oswal wrote:
> DC Servo register 57h holds the DC offset value after the hardware has
> completed the DC Servo Correction, so declare this register as volatile
> because it is changed by the hardware.
> 
> Signed-off-by: Nikesh Oswal <nikesh@...nsource.wolfsonmicro.com>
> ---
>  drivers/mfd/wm8994-regmap.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mfd/wm8994-regmap.c b/drivers/mfd/wm8994-regmap.c
> index 2fbce9c..fa1630d 100644
> --- a/drivers/mfd/wm8994-regmap.c
> +++ b/drivers/mfd/wm8994-regmap.c
> @@ -1169,6 +1169,7 @@ static bool wm8958_volatile_register(struct device *dev, unsigned int reg)
>  	case WM8958_FW_MINOR_0:
>  	case WM8958_FW_PATCH_1:
>  	case WM8958_FW_PATCH_0:
> +	case WM8994_DC_SERVO_4:

Looking at this again it looks like this should actually be in
wm8994_volatile_register as some revs of the wm8994 use this
register as well as the 8958 for the servo readback.

Then if you update the other patch to use this register for
dsc_readback_mode = 1, then once we have a confirmation
from hardware I think both of these patches are good to go.

Thanks,
Charles

>  		return true;
>  	default:
>  		return wm8994_volatile_register(dev, reg);
> -- 
> 1.7.9.5
> 
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> patches@...nsource.wolfsonmicro.com
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