iio: adc: stm32-adc: use generic binding for sample-time

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>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20211014131228.4692-8-olivier.moysan@foss.st.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 5269bb87d094de4421f1eeff79050560e354b691..6245434f8377954b635a6e6db556500b75acbd67 100644 (file)
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1805,6 +1805,13 @@ 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
+        */
+       if (channel == adc->int_ch[STM32_ADC_INT_CH_VREFINT])
+               smp_ns = max(smp_ns, adc->cfg->ts_vrefint_ns);
+
        /* Determine sampling time (ADC clock cycles) */
        period_ns = NSEC_PER_SEC / adc->common->rate;
        for (smp = 0; smp <= STM32_ADC_MAX_SMP; smp++)
@@ -1881,6 +1888,13 @@ 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;
 }
 
@@ -1896,6 +1910,7 @@ 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",
@@ -1938,6 +1953,19 @@ 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;
 }
 
@@ -2030,6 +2058,19 @@ 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-ns", &val);
+               /* st,min-sample-time-ns 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-ns property %d\n",
+                               ret);
+                       goto err;
+               }
+
                scan_index++;
        }
 
@@ -2048,7 +2089,6 @@ 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++)
@@ -2076,13 +2116,6 @@ 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++;
 
@@ -2099,27 +2132,6 @@ 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 = max(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];