Re: [PATCH V6 1/2] iio: adc: spmi-vadc: Update function for generic voltage conversion

[Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On 09/12/16 15:01, Rama Krishna Phani A wrote:
> Several channels are supported in ADC of PMIC which can be used to
> measure voltage, temperature, current etc., Hardware provides
> readings for all channels in adc code. That adc code needs to be
> converted to voltage. Logic for conversion of adc code to voltage
> is common for all ADC channels(voltage, temperature, current
> .,etc). Implement separate function for generic conversion logic.
> 
> Signed-off-by: Rama Krishna Phani A <rphani-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Applied to the togreg branch of iio.git. Will be initially pushed out as
testing for the autobuilders to play with it.

thanks,

Jonathan
> ---
>  drivers/iio/adc/qcom-spmi-vadc.c | 52 +++++++++++++++++++++-------------------
>  1 file changed, 28 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
> index c2babe5..93c0639 100644
> --- a/drivers/iio/adc/qcom-spmi-vadc.c
> +++ b/drivers/iio/adc/qcom-spmi-vadc.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (c) 2012-2014, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2012-2016, The Linux Foundation. All rights reserved.
>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License version 2 and
> @@ -468,27 +468,38 @@ static int vadc_measure_ref_points(struct vadc_priv *vadc)
>  	return ret;
>  }
>  
> -static s32 vadc_calibrate(struct vadc_priv *vadc,
> -			  const struct vadc_channel_prop *prop, u16 adc_code)
> +static void vadc_scale_calib(struct vadc_priv *vadc, u16 adc_code,
> +			     const struct vadc_channel_prop *prop,
> +			     s64 *scale_voltage)
>  {
> -	const struct vadc_prescale_ratio *prescale;
> -	s64 voltage;
> +	*scale_voltage = (adc_code -
> +		vadc->graph[prop->calibration].gnd);
> +	*scale_voltage *= vadc->graph[prop->calibration].dx;
> +	*scale_voltage = div64_s64(*scale_voltage,
> +		vadc->graph[prop->calibration].dy);
> +	if (prop->calibration == VADC_CALIB_ABSOLUTE)
> +		*scale_voltage +=
> +		vadc->graph[prop->calibration].dx;
>  
> -	voltage = adc_code - vadc->graph[prop->calibration].gnd;
> -	voltage *= vadc->graph[prop->calibration].dx;
> -	voltage = div64_s64(voltage, vadc->graph[prop->calibration].dy);
> +	if (*scale_voltage < 0)
> +		*scale_voltage = 0;
> +}
>  
> -	if (prop->calibration == VADC_CALIB_ABSOLUTE)
> -		voltage += vadc->graph[prop->calibration].dx;
> +static int vadc_scale_volt(struct vadc_priv *vadc,
> +			   const struct vadc_channel_prop *prop, u16 adc_code,
> +			   int *result_uv)
> +{
> +	const struct vadc_prescale_ratio *prescale;
> +	s64 voltage = 0, result = 0;
>  
> -	if (voltage < 0)
> -		voltage = 0;
> +	vadc_scale_calib(vadc, adc_code, prop, &voltage);
>  
>  	prescale = &vadc_prescale_ratios[prop->prescale];
> -
>  	voltage = voltage * prescale->den;
> +	result = div64_s64(voltage, prescale->num);
> +	*result_uv = result;
>  
> -	return div64_s64(voltage, prescale->num);
> +	return 0;
>  }
>  
>  static int vadc_decimation_from_dt(u32 value)
> @@ -552,11 +563,8 @@ static int vadc_read_raw(struct iio_dev *indio_dev,
>  		if (ret)
>  			break;
>  
> -		*val = vadc_calibrate(vadc, prop, adc_code);
> +		vadc_scale_volt(vadc, prop, adc_code, val);
>  
> -		/* 2mV/K, return milli Celsius */
> -		*val /= 2;
> -		*val -= KELVINMIL_CELSIUSMIL;
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_RAW:
>  		prop = &vadc->chan_props[chan->address];
> @@ -564,12 +572,8 @@ static int vadc_read_raw(struct iio_dev *indio_dev,
>  		if (ret)
>  			break;
>  
> -		*val = vadc_calibrate(vadc, prop, adc_code);
> +		*val = (int)adc_code;
>  		return IIO_VAL_INT;
> -	case IIO_CHAN_INFO_SCALE:
> -		*val = 0;
> -		*val2 = 1000;
> -		return IIO_VAL_INT_PLUS_MICRO;
>  	default:
>  		ret = -EINVAL;
>  		break;
> @@ -617,7 +621,7 @@ struct vadc_channels {
>  
>  #define VADC_CHAN_VOLT(_dname, _pre)					\
>  	VADC_CHAN(_dname, IIO_VOLTAGE,					\
> -		  BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),	\
> +		  BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_PROCESSED),\
>  		  _pre)							\
>  
>  /*
>