Re: [Linux-stm32] [PATCH v2 7/7] iio: adc: stm32-adc: use generic binding for sample-time

[Fabrice Gasnier <fabrice.gasnier@foss.st.com>]

On 9/22/21 5:34 PM, Olivier Moysan wrote:
> Add st,min-sample-time-nsecs to channel generic binding.
> Sample time can be defined par channel node. If a channel
> is configured as differential, the same sample time applies
> for both inputs.
> Keep support of legacy st,min-sample-time-nsecs property
> for backward compatibility.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  drivers/iio/adc/stm32-adc.c | 70 +++++++++++++++++++++----------------
>  1 file changed, 39 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index c427e439bf4a..cfd11ff0cf36 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1809,6 +1809,11 @@ static void stm32_adc_smpr_init(struct stm32_adc *adc, int channel, u32 smp_ns)
>  	u32 period_ns, shift = smpr->shift, mask = smpr->mask;
>  	unsigned int smp, r = smpr->reg;
>  
> +	/*
> +	 * For vrefint channel, ensure that the sampling time cannot
> +	 * be lower than the one specified in the datasheet
> +	 */
> +

Hi Olivier,

I had a quick look at this series. It looks like some code is missing
here, e.g. to check "ts_vrefint_ns".

Thanks & BR,
Fabrice

>  	/* Determine sampling time (ADC clock cycles) */
>  	period_ns = NSEC_PER_SEC / adc->common->rate;
>  	for (smp = 0; smp <= STM32_ADC_MAX_SMP; smp++)
> @@ -1885,6 +1890,13 @@ static int stm32_adc_get_legacy_chan_count(struct iio_dev *indio_dev, struct stm
>  		num_channels += ret;
>  	}
>  
> +	/* Optional sample time is provided either for each, or all channels */
> +	ret = of_property_count_u32_elems(node, "st,min-sample-time-nsecs");
> +	if (ret > 1 && ret != num_channels) {
> +		dev_err(&indio_dev->dev, "Invalid st,min-sample-time-nsecs\n");
> +		return -EINVAL;
> +	}
> +
>  	return num_channels;
>  }
>  
> @@ -1900,6 +1912,7 @@ static int stm32_adc_legacy_chan_init(struct iio_dev *indio_dev,
>  	int scan_index = 0, val, ret, i;
>  	struct property *prop;
>  	const __be32 *cur;
> +	u32 smp = 0;
>  
>  	if (num_diff) {
>  		ret = of_property_read_u32_array(node, "st,adc-diff-channels",
> @@ -1942,6 +1955,19 @@ static int stm32_adc_legacy_chan_init(struct iio_dev *indio_dev,
>  		scan_index++;
>  	}
>  
> +	for (i = 0; i < scan_index; i++) {
> +		/*
> +		 * Using of_property_read_u32_index(), smp value will only be
> +		 * modified if valid u32 value can be decoded. This allows to
> +		 * get either no value, 1 shared value for all indexes, or one
> +		 * value per channel.
> +		 */
> +		of_property_read_u32_index(node, "st,min-sample-time-nsecs", i, &smp);
> +
> +		/* Prepare sampling time settings */
> +		stm32_adc_smpr_init(adc, channels[i].channel, smp);
> +	}
> +
>  	return scan_index;
>  }
>  
> @@ -2034,6 +2060,19 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
>  
>  		stm32_adc_chan_init_one(indio_dev, &channels[scan_index], val,
>  					vin[1], scan_index, differential);
> +
> +		ret = of_property_read_u32(child, "st,min-sample-time-nsecs", &val);
> +		/* st,min-sample-time-nsecs is optional */
> +		if (!ret) {
> +			stm32_adc_smpr_init(adc, channels[scan_index].channel, val);
> +			if (differential)
> +				stm32_adc_smpr_init(adc, vin[1], val);
> +		} else if (ret != -EINVAL) {
> +			dev_err(&indio_dev->dev, "Invalid st,min-sample-time-nsecs property %d\n",
> +				ret);
> +			goto err;
> +		}
> +
>  		scan_index++;
>  	}
>  
> @@ -2052,7 +2091,6 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  	const struct stm32_adc_info *adc_info = adc->cfg->adc_info;
>  	struct iio_chan_spec *channels;
>  	int scan_index = 0, num_channels = 0, ret, i;
> -	u32 smp = 0;
>  	bool legacy = false;
>  
>  	for (i = 0; i < STM32_ADC_INT_CH_NB; i++)
> @@ -2080,13 +2118,6 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  		return -EINVAL;
>  	}
>  
> -	/* Optional sample time is provided either for each, or all channels */
> -	ret = of_property_count_u32_elems(node, "st,min-sample-time-nsecs");
> -	if (ret > 1 && ret != num_channels) {
> -		dev_err(&indio_dev->dev, "Invalid st,min-sample-time-nsecs\n");
> -		return -EINVAL;
> -	}
> -
>  	if (timestamping)
>  		num_channels++;
>  
> @@ -2103,29 +2134,6 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  		return ret;
>  	scan_index = ret;
>  
> -	for (i = 0; i < scan_index; i++) {
> -		/*
> -		 * Using of_property_read_u32_index(), smp value will only be
> -		 * modified if valid u32 value can be decoded. This allows to
> -		 * get either no value, 1 shared value for all indexes, or one
> -		 * value per channel.
> -		 */
> -		of_property_read_u32_index(node, "st,min-sample-time-nsecs",
> -					   i, &smp);
> -
> -		/*
> -		 * For vrefint channel, ensure that the sampling time cannot
> -		 * be lower than the one specified in the datasheet
> -		 */
> -		if (channels[i].channel == adc->int_ch[STM32_ADC_INT_CH_VREFINT] &&
> -		    smp < adc->cfg->ts_vrefint_ns) {
> -			smp = adc->cfg->ts_vrefint_ns;
> -		}
> -
> -		/* Prepare sampling time settings */
> -		stm32_adc_smpr_init(adc, channels[i].channel, smp);
> -	}
> -
>  	if (timestamping) {
>  		struct iio_chan_spec *timestamp = &channels[scan_index];
>  
>