Re: [PATCH] iio: bmp280: properly initialize device for humidity reading

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 25 Jul 2017 11:11:14 +0200
Andreas Klinger <ak@it-klinger.de> wrote:

> If the device is not initialized at least once it happens that the humidity
> reading is skipped, which means the special value 0x8000 is delivered.
> 
> For omitting this case the oversampling of the humidity must be set before
> the oversampling of the temperature und pressure is set as written in the
> datasheet of the BME280.
> 
> Furthermore proper error detection is added in case a skipped value is read
> from the device. This is done also for pressure and temperature reading.
> Especially it don't make sense to compensate this value and treat it as
> regular value.
> 
> Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Applied to the fixes togreg branch of iio.git.

Thanks,

Jonathan
> ---
>  drivers/iio/pressure/bmp280-core.c | 27 ++++++++++++++++++++++++---
>  drivers/iio/pressure/bmp280.h      |  5 +++++
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> index 4d18826ac63c..d434e2c23833 100644
> --- a/drivers/iio/pressure/bmp280-core.c
> +++ b/drivers/iio/pressure/bmp280-core.c
> @@ -281,6 +281,11 @@ static int bmp280_read_temp(struct bmp280_data *data,
>  	}
>  
>  	adc_temp = be32_to_cpu(tmp) >> 12;
> +	if (adc_temp == BMP280_TEMP_SKIPPED) {
> +		/* reading was skipped */
> +		dev_err(data->dev, "reading temperature skipped\n");
> +		return -EIO;
> +	}
>  	comp_temp = bmp280_compensate_temp(data, adc_temp);
>  
>  	/*
> @@ -316,6 +321,11 @@ static int bmp280_read_press(struct bmp280_data *data,
>  	}
>  
>  	adc_press = be32_to_cpu(tmp) >> 12;
> +	if (adc_press == BMP280_PRESS_SKIPPED) {
> +		/* reading was skipped */
> +		dev_err(data->dev, "reading pressure skipped\n");
> +		return -EIO;
> +	}
>  	comp_press = bmp280_compensate_press(data, adc_press);
>  
>  	*val = comp_press;
> @@ -344,6 +354,11 @@ static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
>  	}
>  
>  	adc_humidity = be16_to_cpu(tmp);
> +	if (adc_humidity == BMP280_HUMIDITY_SKIPPED) {
> +		/* reading was skipped */
> +		dev_err(data->dev, "reading humidity skipped\n");
> +		return -EIO;
> +	}
>  	comp_humidity = bmp280_compensate_humidity(data, adc_humidity);
>  
>  	*val = comp_humidity;
> @@ -596,14 +611,20 @@ static const struct bmp280_chip_info bmp280_chip_info = {
>  
>  static int bme280_chip_config(struct bmp280_data *data)
>  {
> -	int ret = bmp280_chip_config(data);
> +	int ret;
>  	u8 osrs = BMP280_OSRS_HUMIDITIY_X(data->oversampling_humid + 1);
>  
> +	/*
> +	 * Oversampling of humidity must be set before oversampling of
> +	 * temperature/pressure is set to become effective.
> +	 */
> +	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_HUMIDITY,
> +				  BMP280_OSRS_HUMIDITY_MASK, osrs);
> +
>  	if (ret < 0)
>  		return ret;
>  
> -	return regmap_update_bits(data->regmap, BMP280_REG_CTRL_HUMIDITY,
> -				  BMP280_OSRS_HUMIDITY_MASK, osrs);
> +	return bmp280_chip_config(data);
>  }
>  
>  static const struct bmp280_chip_info bme280_chip_info = {
> diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
> index 2c770e13be0e..61347438b779 100644
> --- a/drivers/iio/pressure/bmp280.h
> +++ b/drivers/iio/pressure/bmp280.h
> @@ -96,6 +96,11 @@
>  #define BME280_CHIP_ID			0x60
>  #define BMP280_SOFT_RESET_VAL		0xB6
>  
> +/* BMP280 register skipped special values */
> +#define BMP280_TEMP_SKIPPED		0x80000
> +#define BMP280_PRESS_SKIPPED		0x80000
> +#define BMP280_HUMIDITY_SKIPPED		0x8000
> +
>  /* Regmap configurations */
>  extern const struct regmap_config bmp180_regmap_config;
>  extern const struct regmap_config bmp280_regmap_config;