linux-kernel - Re: [PATCH] iio: humidity: hts221: Fix sensor reads after resume

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Date:   Mon, 07 May 2018 10:21:28 +0800
From:   Shrirang Bagul <shrirang.bagul@...onical.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     lorenzo.bianconi83@...il.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: humidity: hts221: Fix sensor reads after resume

On Sun, 2018-05-06 at 17:19 +0100, Jonathan Cameron wrote:
> On Mon, 30 Apr 2018 12:25:46 +0800
> Shrirang Bagul <shrirang.bagul@...onical.com> wrote:
> 
> > CTRL1 register (ODR & BDU settings) gets reset after system comes back
> > from suspend, causing subsequent reads from the sensor to fail.
> > 
> > This patch restores the CTRL1 register after resume.
> > 
> > Based on:
> > git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git iio-fixes-for-4.14b
> > 
> > Since 4.17.rc1, this driver uses REGMAP; I'll send a separate patch to
> > address this issue.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: ffebe74b7c95 (iio: humidity: hts221: avoid useless ODR reconfiguration)
> 
> Looks like part of the problem was introduced in that patch, part well predated
> it (BDU).
> 
> > Signed-off-by: Shrirang Bagul <shrirang.bagul@...onical.com>
> 
> As you way, this needs to be a bit different to take into account
> the change to regmap.  We'll need to have that upstream before we look
> at a back port.  One element inline surprises me and needs further
> explanation.
I have sent a patch based on iio-for-4.17b [1], Lorenzo and I are still 
discussing our findings. It's not just the CTRL1 reg, but also the AV_CONF(0x10) reg.
which loses it's contents coming out of suspend.

[1] https://marc.info/?l=linux-iio&m=152534455701742&w=2
> 
> 
> > ---
> >  drivers/iio/humidity/hts221_core.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
> > index 32524a8dc66f..fed2da64fa3b 100644
> > --- a/drivers/iio/humidity/hts221_core.c
> > +++ b/drivers/iio/humidity/hts221_core.c
> > @@ -674,11 +674,15 @@ static int __maybe_unused hts221_resume(struct device *dev)
> >  	struct hts221_hw *hw = iio_priv(iio_dev);
> >  	int err = 0;
> >  
> > -	if (hw->enabled)
> > -		err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
> > -					     HTS221_ENABLE_MASK, true);
> 
> Why drop the enable setting?  Seems that we want to do this 'as well',
> if the device was previous enabled.
Yes, will cover this in v2.
> 
> > +	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
> > +				     HTS221_BDU_MASK, 1);
> > +	if (err < 0)
> > +		goto fail_err;
> >  
> > -	return err;
> > +	err = hts221_update_odr(hw, hw->odr);
> > +
> > +fail_err:
> > +	return err < 0 ? err : 0;
> >  }
> >  
> >  const struct dev_pm_ops hts221_pm_ops = {
> 
> 
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