Add scaling support to STM32 DFSDM.
Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxxxxxxx>
---
drivers/iio/adc/Kconfig | 1 +
drivers/iio/adc/stm32-dfsdm-adc.c | 94 ++++++++++++++++++++++++++++++-
2 files changed, 92 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index f3dfdaa80678..858ae8161fa4 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1223,6 +1223,7 @@ config STM32_DFSDM_ADC
select IIO_BUFFER
select IIO_BUFFER_HW_CONSUMER
select IIO_TRIGGERED_BUFFER
+ select IIO_BACKEND
help
Select this option to support ADCSigma delta modulator for
STMicroelectronics STM32 digital filter for sigma delta converter.
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
@@ -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>
@@ -78,6 +79,7 @@ struct stm32_dfsdm_adc {
/* ADC specific */
unsigned int oversamp;
struct iio_hw_consumer *hwc;
+ struct iio_backend **backend;
struct completion completion;
u32 *buffer;
@@ -672,6 +674,8 @@ static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
struct fwnode_handle *node)
{
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;
@@ -721,6 +725,14 @@ static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
if (ret != -EINVAL)
df_ch->alt_si = 0;
+ if (adc->dev_data->type == DFSDM_IIO) {
+ backend = devm_iio_backend_subnode_get(&indio_dev->dev, NULL, node);
+ if (IS_ERR(backend))
+ return dev_err_probe(&indio_dev->dev, PTR_ERR(backend),
+ "Failed to get backend\n");
+ adc->backend[ch->scan_index] = backend;
+ }
+
return 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;
/* 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]) {
+ 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++;
+ }
+ }
+
if (adc->hwc)
iio_hw_consumer_disable(adc->hwc);
@@ -1282,7 +1311,14 @@ 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:
@@ -1291,6 +1327,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
return ret;
if (adc->hwc)
ret = iio_hw_consumer_enable(adc->hwc);
+ if (adc->backend[idx])
+ ret = iio_backend_enable(&indio_dev->dev, adc->backend[idx]);
if (ret < 0) {
dev_err(&indio_dev->dev,
"%s: IIO enable failed (channel %d)\n",
@@ -1301,6 +1339,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
ret = stm32_dfsdm_single_conv(indio_dev, chan, val);
if (adc->hwc)
iio_hw_consumer_disable(adc->hwc);
+ if (adc->backend[idx])
+ iio_backend_disable(&indio_dev->dev, adc->backend[idx]);
if (ret < 0) {
dev_err(&indio_dev->dev,
"%s: Conversion failed (channel %d)\n",
@@ -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.
+ * 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],
+ * 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.
+ */
+ 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);
+ } 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);
--
2.25.1
