Add scaling support to STM32 DFSDM.
Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxxxxxxx>
---
drivers/iio/adc/stm32-dfsdm-adc.c | 77 +++++++++++++++++++++++++++++--
1 file changed, 73 insertions(+), 4 deletions(-)
diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index 96f4e0c64cdc..dba1a8ef5451 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -9,6 +9,7 @@
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/iio/adc/stm32-dfsdm-adc.h>
+#include <linux/iio/backend.h>
#include <linux/iio/buffer.h>
#include <linux/iio/hw-consumer.h>
#include <linux/iio/sysfs.h>
@@ -77,6 +78,7 @@ struct stm32_dfsdm_adc {
/* ADC specific */
unsigned int oversamp;
+ struct iio_backend **backend;
struct completion completion;
u32 *buffer;
@@ -600,6 +602,8 @@ static int stm32_dfsdm_channel_parse_of(struct stm32_dfsdm *dfsdm,
struct iio_chan_spec *ch)
{
struct stm32_dfsdm_channel *df_ch;
+ struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+ struct iio_backend *backend;
const char *of_str;
int ret, val;
@@ -648,6 +652,12 @@ static int stm32_dfsdm_channel_parse_of(struct stm32_dfsdm *dfsdm,
if (ret != -EINVAL)
df_ch->alt_si = 0;
+ backend = fwnode_iio_backend_get(node, 0);
+ if (IS_ERR(backend))
+ return dev_err_probe(&indio_dev->dev, PTR_ERR(backend), "Failed to get backend\n");
+
+ adc->backend[df_ch->id] = backend;
+
return 0;
}
@@ -1091,7 +1101,7 @@ static int stm32_dfsdm_single_conv(struct iio_dev *indio_dev,
{
struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
long timeout;
- int ret;
+ int ret, idx = chan->scan_index;
reinit_completion(&adc->completion);
@@ -1101,6 +1111,13 @@ static int stm32_dfsdm_single_conv(struct iio_dev *indio_dev,
if (ret < 0)
return ret;
+ if (!adc->backend[idx]->ops->enable)
+ return -EINVAL;
+
+ ret = adc->backend[idx]->ops->enable(adc->backend[idx]);
+ if (ret < 0)
+ return ret;
+
ret = regmap_update_bits(adc->dfsdm->regmap, DFSDM_CR2(adc->fl_id),
DFSDM_CR2_REOCIE_MASK, DFSDM_CR2_REOCIE(1));
if (ret < 0)
@@ -1134,6 +1151,8 @@ static int stm32_dfsdm_single_conv(struct iio_dev *indio_dev,
stm32_dfsdm_process_data(adc, res);
stop_dfsdm:
+ ret = adc->backend[idx]->ops->disable(adc->backend[idx]);
+
stm32_dfsdm_stop_dfsdm(adc->dfsdm);
return ret;
@@ -1198,7 +1217,14 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
int *val2, long mask)
{
struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
- int ret;
+
+ struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
+ struct stm32_dfsdm_filter_osr *flo = &fl->flo[fl->fast];
+ u32 max = flo->max << (flo->lshift - chan->scan_type.shift);
+ int ret, idx = chan->scan_index;
+
+ if (flo->lshift < chan->scan_type.shift)
+ max = flo->max >> (chan->scan_type.shift - flo->lshift);
switch (mask) {
case IIO_CHAN_INFO_RAW:
@@ -1232,6 +1258,41 @@ 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.
+ * This leads to underestimating input voltage. To
+ * compensate this deviation, the voltage reference can be
+ * corrected with a factor = realbits resolution / actual max
+ */
+ adc->backend[idx]->ops->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],
+ * with n=realbits-1.
+ * - 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.
+ * Add 2^n to offset. (i.e. middle of input range)
+ * offset = offset(sd) * vref / res(sd) * max / vref.
+ */
+ adc->backend[idx]->ops->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;
@@ -1360,7 +1421,10 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
* 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);
+ ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE) |
+ BIT(IIO_CHAN_INFO_OFFSET);
+
ch->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
BIT(IIO_CHAN_INFO_SAMP_FREQ);
@@ -1451,7 +1515,12 @@ static int stm32_dfsdm_adc_init(struct device *dev, struct iio_dev *indio_dev)
if (!ch)
return -ENOMEM;
- stm32_dfsdm_generic_chan_init(indio_dev, adc, ch);
+ adc->backend = devm_kzalloc(&indio_dev->dev, sizeof(*adc->backend) * adc->dfsdm->num_chs,
+ GFP_KERNEL);
+ if (!adc->backend)
+ return -ENOMEM;
+
+ ret = stm32_dfsdm_generic_chan_init(indio_dev, adc, ch);
if (ret < 0)
return ret;
--
2.25.1
