Hi Jonathan,
On 6/23/24 17:21, Jonathan Cameron wrote:
On Tue, 18 Jun 2024 18:08:34 +0200
Olivier Moysan <olivier.moysan@xxxxxxxxxxx> wrote:
Add scaling support to STM32 DFSDM.
Perhaps a short description here of how this works? Where does the scale come
from, what assumptions are made etc.
Sure. Requires more explanations. Done
Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxxxxxxx>
Some minor stuff.
diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index 69b4764d7cba..93bf6035bd6d 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
urn 0;
}
@@ -1060,7 +1072,7 @@ static int stm32_dfsdm_update_scan_mode(struct iio_dev *indio_dev,
static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
{
struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
- int ret;
+ int i = 0, ret;
Don't mix assigned and unassigned variable declarations. Just use a separate line
as this can mean subtle assignment or lack of assignment issues sneak in.
Ack
/* Reset adc buffer index */
adc->bufi = 0;
@@ -1071,6 +1083,15 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
return ret;
}
+ if (adc->backend) {
+ while (adc->backend[i]) {
Could do similar to the suggestion below.
Mostly I don't like the index variable manipulation.
+ ret = iio_backend_enable(&indio_dev->dev, adc->backend[i]);
+ if (ret < 0)
+ return ret;
+ i++;
+ }
+ }
+
ret = stm32_dfsdm_start_dfsdm(adc->dfsdm);
if (ret < 0)
goto err_stop_hwc;
@@ -1103,6 +1124,7 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
{
struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+ int i = 0;
stm32_dfsdm_stop_conv(indio_dev);
@@ -1110,6 +1132,13 @@ static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
stm32_dfsdm_stop_dfsdm(adc->dfsdm);
+ if (adc->backend) {
+ while (adc->backend[i]) {
+ iio_backend_disable(&indio_dev->dev, adc->backend[i]);
+ i++;
+ }
Something like
struct iio_backend **be = &adc->backend[0];
do {
iio_backend_disable(&indio-dev->dev, be);
} while (be++);
maybe. Up to you.
If you don't mind, I will keep indexes. Pointers here looks more
difficult to read, and pre/post incrementation in the loop condition can
easily introduce bugs, imho.
+ }
@@ -1320,6 +1360,45 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
*val = adc->sample_freq;
return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ /*
+ * Scale is expressed in mV.
+ * When fast mode is disabled, actual resolution may be lower
+ * than 2^n, where n=realbits-1.
As below, use a few more spaces.
+ * This leads to underestimating input voltage. To
+ * compensate this deviation, the voltage reference can be
+ * corrected with a factor = realbits resolution / actual max
+ */
+ if (adc->backend[idx]) {
+ iio_backend_read_raw(adc->backend[idx], val, val2, mask);
+
+ *val = div_u64((u64)*val * (u64)BIT(DFSDM_DATA_RES - 1), max);
+ *val2 = chan->scan_type.realbits;
+ if (chan->differential)
+ *val *= 2;
+ }
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ case IIO_CHAN_INFO_OFFSET:
+ /*
+ * DFSDM output data are in the range [-2^n,2^n],
Use a few more spaces. [-2^2, 2^n]
+ * with n=realbits-1.
n = realbits - 1
Just to keep it closer to the C coding style.
Done
+ * - Differential modulator:
+ * Offset correspond to SD modulator offset.
+ * - Single ended modulator:
+ * Input is in [0V,Vref] range, where 0V corresponds to -2^n, and Vref to 2^n.
Avoid that long line with a suitable line break.
Ack
+ * Add 2^n to offset. (i.e. middle of input range)
+ * offset = offset(sd) * vref / res(sd) * max / vref.
+ */
+ if (adc->backend[idx]) {
+ iio_backend_read_raw(adc->backend[idx], val, val2, mask);
+
+ *val = div_u64((u64)max * *val, BIT(*val2 - 1));
+ if (!chan->differential)
+ *val += max;
+ }
+ return IIO_VAL_INT;
}
return -EINVAL;
@@ -1449,7 +1528,15 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev, struct iio_c
* IIO_CHAN_INFO_RAW: used to compute regular conversion
* IIO_CHAN_INFO_OVERSAMPLING_RATIO: used to set oversampling
*/
- ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+ if (child) {
+ ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE) |
+ BIT(IIO_CHAN_INFO_OFFSET);
Indent looks a little odd. Maybe one more space neede?
Ack
+ } else {
+ /* Legacy. Scaling not supported */
+ ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+ }
+
ch->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
BIT(IIO_CHAN_INFO_SAMP_FREQ);
@@ -1816,3 +1903,4 @@ module_platform_driver(stm32_dfsdm_adc_driver);
MODULE_DESCRIPTION("STM32 sigma delta ADC");
MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>");
MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(IIO_BACKEND);
BRs
Olivier
