[PATCH v2 06/10] iio: adc: mcp3911: add support for oversampling ratio

Marcus Folkesson
2022-06-25T10:37:30Z

The chip supports oversampling ratio, so expose it to userspace.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
---

Notes:
v2:
- Make use of osr table
- Change formatting and typos

drivers/iio/adc/mcp3911.c | 47 +++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
index f4ee0c27c2ab..1469c12ebbb2 100644
--- a/drivers/iio/adc/mcp3911.c
+++ b/drivers/iio/adc/mcp3911.c
@@ -5,6 +5,8 @@
* Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@gmail.com>
* Copyright (C) 2018 Kent Gustavsson <kent@minoris.se>
*/
+#include <linux/bitfield.h>
+#include <linux/bits.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
@@ -35,6 +37,7 @@
#define MCP3911_REG_CONFIG 0x0c
#define MCP3911_CONFIG_CLKEXT BIT(1)
#define MCP3911_CONFIG_VREFEXT BIT(2)
+#define MCP3911_CONFIG_OSR GENMASK(13, 11)

#define MCP3911_REG_OFFCAL_CH0 0x0e
#define MCP3911_REG_GAINCAL_CH0 0x11
@@ -53,6 +56,8 @@

#define MCP3911_NUM_CHANNELS 2

+static const int mcp3911_osr_table[] = {32, 64, 128, 256, 512, 1024, 2048, 4096};
+
struct mcp3911 {
struct spi_device *spi;
struct mutex lock;
@@ -108,6 +113,22 @@ static int mcp3911_update(struct mcp3911 *adc, u8 reg, u32 mask,
return mcp3911_write(adc, reg, val, len);
}

+static int mcp3911_read_avail(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ const int **vals, int *type, int *length,
+ long info)
+{
+ switch (info) {
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ *type = IIO_VAL_INT;
+ *vals = mcp3911_osr_table;
+ *length = ARRAY_SIZE(mcp3911_osr_table);
+ return IIO_AVAIL_LIST;
+ default:
+ return -EINVAL;
+ }
+}
+
static int mcp3911_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *channel, int *val,
int *val2, long mask)
@@ -134,6 +155,16 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,

ret = IIO_VAL_INT;
break;
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ ret = mcp3911_read(adc,
+ MCP3911_REG_CONFIG, val, 2);
+ if (ret)
+ goto out;
+
+ *val = FIELD_GET(MCP3911_CONFIG_OSR, *val);
+ *val = 32 << *val;
+ ret = IIO_VAL_INT;
+ break;

case IIO_CHAN_INFO_SCALE:
if (adc->vref) {
@@ -186,6 +217,17 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
MCP3911_STATUSCOM_EN_OFFCAL,
MCP3911_STATUSCOM_EN_OFFCAL, 2);
break;
+
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ for (int i = 0; i < sizeof(mcp3911_osr_table); i++) {
+ if (val == mcp3911_osr_table[i]) {
+ val = FIELD_PREP(MCP3911_CONFIG_OSR, i);
+ ret = mcp3911_update(adc, MCP3911_REG_CONFIG, MCP3911_CONFIG_OSR,
+ val, 2);
+ break;
+ }
+ }
+ break;
}

out:
@@ -198,9 +240,13 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
.indexed = 1, \
.channel = idx, \
.scan_index = idx, \
+ .scan_index = idx, \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
BIT(IIO_CHAN_INFO_OFFSET) | \
BIT(IIO_CHAN_INFO_SCALE), \
+ .info_mask_shared_by_type_available = \
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
.scan_type = { \
.sign = 's', \
.realbits = 24, \
@@ -252,6 +298,7 @@ static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
static const struct iio_info mcp3911_info = {
.read_raw = mcp3911_read_raw,
.write_raw = mcp3911_write_raw,
+ .read_avail = mcp3911_read_avail,
};

static irqreturn_t mcp3911_interrupt(int irq, void *dev_id)
--
2.36.1