Re: [PATCH v4] iio: mlx90614: Implement filter configuration

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On Mon, 17 Aug 2015, Crt Mori wrote:

> Implemented Low pass 3db frequency filter which configures
> FIR and IIR values within the configuration register of EEPROM.
> For more standardized interface we have fixed the FIR value
> to 1024, while changes in IIR value are directly connected to
> filter responses. The new datasheet version will provide a
> simplified table (also in reStructured text format below) with
> this change, to provide quick overview of possible settings.

see comment below
 
> Below sensor timings (bandwidth) are calculated for 3db frequency
> low pass filter.
> 
> +--------------------+-----------------+
> | Filter setting (%) | Band width (Hz) |
> |  (rounded to 1.0)  |                 |
> +====================+=================+
> |         13         |      0.15       |
> +--------------------+-----------------+
> |         17         |      0.20       |
> +--------------------+-----------------+
> |         25         |      0.31       |
> +--------------------+-----------------+
> |         50         |      0.77       |
> +--------------------+-----------------+
> |         57         |      0.86       |
> +--------------------+-----------------+
> |         67         |      1.10       |
> +--------------------+-----------------+
> |         80         |      1.53       |
> +--------------------+-----------------+
> |        100         |      7.23       |
> +--------------------+-----------------+
> 
> The diff is made towards togreg branch. Added myself to MAINTAINERS and
> authors as per discussion with Jonathan.
> 
> Signed-off-by: Crt Mori <cmo@xxxxxxxxxxx>
> ---
>  MAINTAINERS                        |  7 +++
>  drivers/iio/temperature/mlx90614.c | 89 ++++++++++++++++++++++++++++++++++++--
>  2 files changed, 93 insertions(+), 3 deletions(-)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 8133cef..f658890 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6739,6 +6739,13 @@ S:	Supported
>  F:	include/linux/mlx5/
>  F:	drivers/infiniband/hw/mlx5/
>  
> +MELEXIS MLX90614 DRIVER
> +M:	Crt Mori <cmo@xxxxxxxxxxx>
> +L:	linux-iio@xxxxxxxxxxxxxxx
> +W:	http://www.melexis.com
> +S:	Supported
> +F:	drivers/iio/temperature/mlx90614.c
> +
>  MN88472 MEDIA DRIVER
>  M:	Antti Palosaari <crope@xxxxxx>
>  L:	linux-media@xxxxxxxxxxxxxxx
> diff --git a/drivers/iio/temperature/mlx90614.c b/drivers/iio/temperature/mlx90614.c
> index 5d033a5..08e2bbf 100644
> --- a/drivers/iio/temperature/mlx90614.c
> +++ b/drivers/iio/temperature/mlx90614.c
> @@ -3,6 +3,7 @@
>   *
>   * Copyright (c) 2014 Peter Meerwald <pmeerw@xxxxxxxxxx>
>   * Copyright (c) 2015 Essensium NV
> + * Copyright (c) 2015 Melexis
>   *
>   * This file is subject to the terms and conditions of version 2 of
>   * the GNU General Public License.  See the file COPYING in the main
> @@ -20,7 +21,6 @@
>   * always has a pull-up so we do not need an extra GPIO to drive it high.  If
>   * the "wakeup" GPIO is not given, power management will be disabled.
>   *
> - * TODO: filter configuration
>   */
>  
>  #include <linux/err.h>
> @@ -32,6 +32,7 @@
>  #include <linux/pm_runtime.h>
>  
>  #include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
>  
>  #define MLX90614_OP_RAM		0x00
>  #define MLX90614_OP_EEPROM	0x20
> @@ -79,6 +80,20 @@ struct mlx90614_data {
>  	unsigned long ready_timestamp; /* in jiffies */
>  };
>  
> +/* Bandwidth values for IIR filtering */
> +static const int mlx90614_iir_values[] = {77, 31, 20, 15, 723, 153, 110, 86};
> +static IIO_CONST_ATTR(in_temp_object_filter_low_pass_3db_frequency_available,
> +		      "0.15 0.20 0.31 0.77 0.86 1.10 1.53 7.23");
> +
> +static struct attribute *mlx90614_attributes[] = {
> +	&iio_const_attr_in_temp_object_filter_low_pass_3db_frequency_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group mlx90614_attr_group = {
> +	.attrs = mlx90614_attributes,
> +};
> +
>  /*
>   * Erase an address and write word.
>   * The mutex must be locked before calling.
> @@ -117,6 +132,41 @@ static s32 mlx90614_write_word(const struct i2c_client *client, u8 command,
>  	return ret;
>  }
>  
> +/*
> + * Find the IIR value inside mlx90614_iir_values array and return its position
> + * which is equivalent to the bit value in sensor register
> + */
> +static inline s32 mlx90614_iir_search(const struct i2c_client *client,
> +				      int value)
> +{
> +	u8 i;

I'd rather use int for the loop variable

> +	s32 ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(mlx90614_iir_values); ++i) {
> +		if (value == mlx90614_iir_values[i])
> +			break;
> +	}
> +
> +	if (value != mlx90614_iir_values[i])

this is an out-of-bound access beyond _iir_values

> +		return -EINVAL;
> +
> +	/*
> +	 * CONFIG register values must not be changed so
> +	 * we must read them before we actually write
> +	 * changes
> +	 */
> +	ret = i2c_smbus_read_word_data(client, MLX90614_CONFIG);

I'd rather do
if (ret < 0)
   return ret;

> +	if (ret >= 0) {
> +		/* Write changed values */
> +		ret = mlx90614_write_word(client, MLX90614_CONFIG,
> +				(i << MLX90614_CONFIG_IIR_SHIFT) |
> +				(((u16) ((0x7 << MLX90614_CONFIG_FIR_SHIFT) |
> +				((u16) ret & (~((u16) MLX90614_CONFIG_FIR_MASK))))) &
> +				(~(u16) MLX90614_CONFIG_IIR_MASK)));

this is still a mess, ehm, not very readable

> +	}
> +	return ret;
> +}
> +
>  #ifdef CONFIG_PM
>  /*
>   * If @startup is true, make sure MLX90614_TIMING_STARTUP ms have elapsed since
> @@ -236,6 +286,21 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
>  			*val2 = ret * MLX90614_CONST_EMISSIVITY_RESOLUTION;
>  		}
>  		return IIO_VAL_INT_PLUS_NANO;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY: /* IIR setting with
> +							     FIR = 1024 */
> +		mlx90614_power_get(data, false);
> +		mutex_lock(&data->lock);
> +		ret = i2c_smbus_read_word_data(data->client, MLX90614_CONFIG);
> +		mutex_unlock(&data->lock);
> +		mlx90614_power_put(data);
> +
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = mlx90614_iir_values[ret & MLX90614_CONFIG_IIR_MASK] / 100;
> +		*val2 = mlx90614_iir_values[ret & MLX90614_CONFIG_IIR_MASK] % 100 *

probably add parenthesis and don't rely on operator precedence for clarity

> +			10000;
> +		return IIO_VAL_INT_PLUS_MICRO;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -263,6 +328,18 @@ static int mlx90614_write_raw(struct iio_dev *indio_dev,
>  		mlx90614_power_put(data);
>  
>  		return ret;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY: /* IIR Filter setting */
> +		if (val < 0 || val2 < 0)
> +			return -EINVAL;
> +
> +		mlx90614_power_get(data, false);
> +		mutex_lock(&data->lock);
> +		ret = mlx90614_iir_search(data->client,
> +					  val * 100 + val2 / 10000);
> +		mutex_unlock(&data->lock);
> +		mlx90614_power_put(data);
> +
> +		return ret;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -275,6 +352,8 @@ static int mlx90614_write_raw_get_fmt(struct iio_dev *indio_dev,
>  	switch (mask) {
>  	case IIO_CHAN_INFO_CALIBEMISSIVITY:
>  		return IIO_VAL_INT_PLUS_NANO;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		return IIO_VAL_INT_PLUS_MICRO;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -294,7 +373,8 @@ static const struct iio_chan_spec mlx90614_channels[] = {
>  		.modified = 1,
>  		.channel2 = IIO_MOD_TEMP_OBJECT,
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> -		    BIT(IIO_CHAN_INFO_CALIBEMISSIVITY),
> +		    BIT(IIO_CHAN_INFO_CALIBEMISSIVITY) |
> +			BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |
>  		    BIT(IIO_CHAN_INFO_SCALE),
>  	},
> @@ -305,7 +385,8 @@ static const struct iio_chan_spec mlx90614_channels[] = {
>  		.channel = 1,
>  		.channel2 = IIO_MOD_TEMP_OBJECT,
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> -		    BIT(IIO_CHAN_INFO_CALIBEMISSIVITY),
> +		    BIT(IIO_CHAN_INFO_CALIBEMISSIVITY) |
> +			BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |
>  		    BIT(IIO_CHAN_INFO_SCALE),
>  	},
> @@ -315,6 +396,7 @@ static const struct iio_info mlx90614_info = {
>  	.read_raw = mlx90614_read_raw,
>  	.write_raw = mlx90614_write_raw,
>  	.write_raw_get_fmt = mlx90614_write_raw_get_fmt,
> +	.attrs = &mlx90614_attr_group,
>  	.driver_module = THIS_MODULE,
>  };
>  
> @@ -569,5 +651,6 @@ module_i2c_driver(mlx90614_driver);
>  
>  MODULE_AUTHOR("Peter Meerwald <pmeerw@xxxxxxxxxx>");
>  MODULE_AUTHOR("Vianney le Clément de Saint-Marcq <vianney.leclement@xxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Crt Mori <cmo@xxxxxxxxxxx>");
>  MODULE_DESCRIPTION("Melexis MLX90614 contactless IR temperature sensor driver");
>  MODULE_LICENSE("GPL");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)

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