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

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Message-ID: <20140813123231.GK15833@opensource.wolfsonmicro.com>
Date:	Wed, 13 Aug 2014 13:32:32 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Nikesh Oswal <nikesh@...nsource.wolfsonmicro.com>
Cc:	alsa-devel@...a-project.org, tiwai@...e.de,
	patches@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org,
	lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz
Subject: Re: [PATCH] mfd: wm8994: declare dc servo register for wm8958 as
	volatile

On Wed, Aug 13, 2014 at 12:13:38PM +0100, Charles Keepax wrote:
> On Wed, Aug 13, 2014 at 11:46:25AM +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 +
> >  include/linux/mfd/wm8994/registers.h |    1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/drivers/mfd/wm8994-regmap.c b/drivers/mfd/wm8994-regmap.c
> > index 2fbce9c..e775565 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 WM8958_DC_SERVO:
> 
> I think you can just use the WM8994_DC_SERVO_4 define the
> register is called DC Servo (4) in the datasheet.
> 
> Also would it be worth adding DC_SERVO_1 and DC_SERVO_READBACK as
> they are being treated as volatile on 8994 and look identical in
> the datasheet.

Sorry missed the call to wm8994_volatile_register ignore this
second comment here.

Thanks,
Charles
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