Re: [PATCH 3/8] iio: adc: ti-ads1015: fix scale information for ADS1115

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 13 Jul 2017 01:31:59 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> The ti-ads1015 driver supports ADS1015 and ADS1115 devices.  The same
> scale information is used for both devices in this driver, however they
> have actually different values and the ADS1115's one is not correct.
> 
> These devices have the same full-scale input voltage range for each PGA
> selection.  So instead of adding another hardcoded scale information,
> compute a correct scale on demand from each device's resolution.
> 
> Cc: Daniel Baluta <daniel.baluta@intel.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Looks good to me.  Cc'd to Daniel's current address.
> ---
>  drivers/iio/adc/ti-ads1015.c | 47 ++++++++++++++++++++++----------------------
>  1 file changed, 23 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
> index 94c2221..1edf323 100644
> --- a/drivers/iio/adc/ti-ads1015.c
> +++ b/drivers/iio/adc/ti-ads1015.c
> @@ -81,18 +81,12 @@ static const unsigned int ads1115_data_rate[] = {
>  	8, 16, 32, 64, 128, 250, 475, 860
>  };
>  
> -static const struct {
> -	int scale;
> -	int uscale;
> -} ads1015_scale[] = {
> -	{3, 0},
> -	{2, 0},
> -	{1, 0},
> -	{0, 500000},
> -	{0, 250000},
> -	{0, 125000},
> -	{0, 125000},
> -	{0, 125000},
> +/*
> + * Translation from PGA bits to full-scale positive and negative input voltage
> + * range in mV
> + */
> +static int ads1015_fullscale_range[] = {
> +	6144, 4096, 2048, 1024, 512, 256, 256, 256
>  };
>  
>  #define ADS1015_V_CHAN(_chan, _addr) {				\
> @@ -300,15 +294,17 @@ static irqreturn_t ads1015_trigger_handler(int irq, void *p)
>  	return IRQ_HANDLED;
>  }
>  
> -static int ads1015_set_scale(struct ads1015_data *data, int chan,
> +static int ads1015_set_scale(struct ads1015_data *data,
> +			     struct iio_chan_spec const *chan,
>  			     int scale, int uscale)
>  {
>  	int i;
> +	int fullscale = div_s64((scale * 1000000LL + uscale) <<
> +				(chan->scan_type.realbits - 1), 1000000);
>  
> -	for (i = 0; i < ARRAY_SIZE(ads1015_scale); i++) {
> -		if (ads1015_scale[i].scale == scale &&
> -		    ads1015_scale[i].uscale == uscale) {
> -			data->channel_data[chan].pga = i;
> +	for (i = 0; i < ARRAY_SIZE(ads1015_fullscale_range); i++) {
> +		if (ads1015_fullscale_range[i] == fullscale) {
> +			data->channel_data[chan->address].pga = i;
>  			return 0;
>  		}
>  	}
> @@ -369,9 +365,9 @@ static int ads1015_read_raw(struct iio_dev *indio_dev,
>  	}
>  	case IIO_CHAN_INFO_SCALE:
>  		idx = data->channel_data[chan->address].pga;
> -		*val = ads1015_scale[idx].scale;
> -		*val2 = ads1015_scale[idx].uscale;
> -		ret = IIO_VAL_INT_PLUS_MICRO;
> +		*val = ads1015_fullscale_range[idx];
> +		*val2 = chan->scan_type.realbits - 1;
> +		ret = IIO_VAL_FRACTIONAL_LOG2;
>  		break;
>  	case IIO_CHAN_INFO_SAMP_FREQ:
>  		idx = data->channel_data[chan->address].data_rate;
> @@ -398,7 +394,7 @@ static int ads1015_write_raw(struct iio_dev *indio_dev,
>  	mutex_lock(&data->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_SCALE:
> -		ret = ads1015_set_scale(data, chan->address, val, val2);
> +		ret = ads1015_set_scale(data, chan, val, val2);
>  		break;
>  	case IIO_CHAN_INFO_SAMP_FREQ:
>  		ret = ads1015_set_data_rate(data, chan->address, val);
> @@ -430,7 +426,10 @@ static const struct iio_buffer_setup_ops ads1015_buffer_setup_ops = {
>  	.validate_scan_mask = &iio_validate_scan_mask_onehot,
>  };
>  
> -static IIO_CONST_ATTR(scale_available, "3 2 1 0.5 0.25 0.125");
> +static IIO_CONST_ATTR_NAMED(ads1015_scale_available, scale_available,
> +	"3 2 1 0.5 0.25 0.125");
> +static IIO_CONST_ATTR_NAMED(ads1115_scale_available, scale_available,
> +	"0.1875 0.125 0.0625 0.03125 0.015625 0.007813");
>  
>  static IIO_CONST_ATTR_NAMED(ads1015_sampling_frequency_available,
>  	sampling_frequency_available, "128 250 490 920 1600 2400 3300");
> @@ -438,7 +437,7 @@ static IIO_CONST_ATTR_NAMED(ads1115_sampling_frequency_available,
>  	sampling_frequency_available, "8 16 32 64 128 250 475 860");
>  
>  static struct attribute *ads1015_attributes[] = {
> -	&iio_const_attr_scale_available.dev_attr.attr,
> +	&iio_const_attr_ads1015_scale_available.dev_attr.attr,
>  	&iio_const_attr_ads1015_sampling_frequency_available.dev_attr.attr,
>  	NULL,
>  };
> @@ -448,7 +447,7 @@ static const struct attribute_group ads1015_attribute_group = {
>  };
>  
>  static struct attribute *ads1115_attributes[] = {
> -	&iio_const_attr_scale_available.dev_attr.attr,
> +	&iio_const_attr_ads1115_scale_available.dev_attr.attr,
>  	&iio_const_attr_ads1115_sampling_frequency_available.dev_attr.attr,
>  	NULL,
>  };