linux-kernel - Re: [PATCH v2] iio: humidity: hts221: Fix sensor reads after resume

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Message-ID: <20180628090525.GA2540@localhost.localdomain>
Date:   Thu, 28 Jun 2018 11:05:26 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Shrirang Bagul <shrirang.bagul@...onical.com>
Cc:     jic23@...nel.org, lorenzo.bianconi83@...il.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        mario.tesi@...com, marco.bianco@...com, armando.visconti@...com
Subject: Re: [PATCH v2] iio: humidity: hts221: Fix sensor reads after resume

> AV_CONF register (RH & TEMP. oversampling ratio's) and CTRL1 register
> (ODR & BDU settings) values are lost after suspend.
> 
> While the change in AV_CONF updates the sensor resolution modes
> (overriding the user configuration before the device went to suspend);
> loss of the contents of the CTRL1 register leads to failure in reading
> sensor output.
> 
> This patch restores the AV_CONF & CTRL1 registers after resume.
> 

Hi Shrirang,

I still suspect we have some hw issue (IoT Gateway) here (cc ST folks
to get more info) and anyway I guess the proposed patch will fix the issue
completely since OD and HL configuration is not restored properly.
Could you please double check HL/OD regs are properly preserved after resume
phase?

Regards,
Lorenzo

> Changes from v1:
> - Don't drop enabling the sensor during resume
> - Restore AV_CONF register along with CTRL1
>   (As demonstrated with i2c register dumps of hts221 captured on Dell
>   IoT Gateways 300x before suspend & after resume [1])
> 
> Fixes: ffebe74b7c95 (iio: humidity: hts221: avoid useless ODR reconfiguration)
> Signed-off-by: Shrirang Bagul <shrirang.bagul@...onical.com>
> 
> [v1] https://marc.info/?l=linux-iio&m=152506543000442&w=2
> [1] https://marc.info/?l=linux-iio&m=152534455701742&w=2
> 
> This patch is based on:
> git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git -b testing
> ---
>  drivers/iio/humidity/hts221_core.c | 31 +++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
> index 166946d4978d..fc5599497f55 100644
> --- a/drivers/iio/humidity/hts221_core.c
> +++ b/drivers/iio/humidity/hts221_core.c
> @@ -656,14 +656,43 @@ static int __maybe_unused hts221_resume(struct device *dev)
>  {
>  	struct iio_dev *iio_dev = dev_get_drvdata(dev);
>  	struct hts221_hw *hw = iio_priv(iio_dev);
> +	const struct hts221_avg *avg;
> +	u8 data, idx;
>  	int err = 0;
>  
> +	/* Restore contents of AV_CONF (RH & TEMP. oversampling ratio's) */
> +	avg = &hts221_avg_list[HTS221_SENSOR_H];
> +	idx = hw->sensors[HTS221_SENSOR_H].cur_avg_idx;
> +	data = avg->avg_avl[idx];
> +	err = hts221_update_avg(hw, HTS221_SENSOR_H, data);
> +	if (err < 0)
> +		goto fail_err;
> +
> +	avg = &hts221_avg_list[HTS221_SENSOR_T];
> +	idx = hw->sensors[HTS221_SENSOR_T].cur_avg_idx;
> +	data = avg->avg_avl[idx];
> +	err = hts221_update_avg(hw, HTS221_SENSOR_T, data);
> +	if (err < 0)
> +		goto fail_err;

just return err, no need for goto statement

> +
> +	/* Restore contents of CTRL1 (BDU & ODR) */
> +	err = regmap_update_bits(hw->regmap, HTS221_REG_CNTRL1_ADDR,
> +				 HTS221_BDU_MASK,
> +				 FIELD_PREP(HTS221_BDU_MASK, 1));
> +	if (err < 0)
> +		goto fail_err;
> +
> +	err = hts221_update_odr(hw, hw->odr);
> +	if (err < 0)
> +		goto fail_err;
> +

just return err, no need for goto statement

>  	if (hw->enabled)
>  		err = regmap_update_bits(hw->regmap, HTS221_REG_CNTRL1_ADDR,
>  					 HTS221_ENABLE_MASK,
>  					 FIELD_PREP(HTS221_ENABLE_MASK,
>  						    true));
> -	return err;
> +fail_err:
> +	return err < 0 ? err : 0;
>  }
>  
>  const struct dev_pm_ops hts221_pm_ops = {
> -- 
> 2.17.1
>