[PATCH v5 7/7] iio: adc: stm32-adc: use generic binding for sample-time

Olivier Moysan
2021-10-14T13:17:06Z

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>
---
drivers/iio/adc/stm32-adc.c | 70 ++++++++++++++++++++++---------------
1 file changed, 41 insertions(+), 29 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 5269bb87d094..6245434f8377 100644
--- 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];