[PATCH 5/5] iio: mcp9600: Add support for IIR filter

[Ben Collins <bcollins@watter.com>]

MCP9600 supports an IIR filter with 7 levels. Add IIR attribute
to allow get/set of this value.

Signed-off-by: Ben Collins <bcollins@watter.com>
---
 drivers/iio/temperature/mcp9600.c | 73 +++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/drivers/iio/temperature/mcp9600.c b/drivers/iio/temperature/mcp9600.c
index 361572a241f06..896520ddf6d3c 100644
--- a/drivers/iio/temperature/mcp9600.c
+++ b/drivers/iio/temperature/mcp9600.c
@@ -31,6 +31,7 @@
 #define MCP9600_STATUS_ALERT(x)		BIT(x)
 #define MCP9600_SENSOR_CFG		0x05
 #define MCP9600_SENSOR_TYPE_MASK	GENMASK(6, 4)
+#define MCP9600_FILTER_MASK		GENMASK(2, 0)
 #define MCP9600_ALERT_CFG1		0x08
 #define MCP9600_ALERT_CFG(x)		(MCP9600_ALERT_CFG1 + (x - 1))
 #define MCP9600_ALERT_CFG_ENABLE	BIT(0)
@@ -94,6 +95,10 @@ static const int mcp9600_tc_types[] = {
 	[THERMOCOUPLE_TYPE_R] = 'R',
 };
 
+static const int mcp_iir_coefficients_avail[] = {
+	1, 2, 4, 8, 16, 32, 64, 128,
+};
+
 static const struct iio_event_spec mcp9600_events[] = {
 	{
 		.type = IIO_EV_TYPE_THRESH,
@@ -118,7 +123,10 @@ static const struct iio_event_spec mcp9600_events[] = {
 			.address = MCP9600_HOT_JUNCTION,		       \
 			.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	       \
 					      BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE) | \
+					      BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY) |  \
 					      BIT(IIO_CHAN_INFO_SCALE),	       \
+			.info_mask_separate_available =                        \
+					      BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY), \
 			.event_spec = &mcp9600_events[hj_ev_spec_off],	       \
 			.num_event_specs = hj_num_ev,			       \
 		},							       \
@@ -161,6 +169,7 @@ struct mcp_chip_info {
 struct mcp9600_data {
 	struct i2c_client *client;
 	u32 thermocouple_type;
+	u8 filter_level; /* Chip default is 0 */
 };
 
 static int mcp9600_read(struct mcp9600_data *data,
@@ -191,13 +200,36 @@ static int mcp9600_read_raw(struct iio_dev *indio_dev,
 		if (ret)
 			return ret;
 		return IIO_VAL_INT;
+
 	case IIO_CHAN_INFO_SCALE:
 		*val = 62;
 		*val2 = 500000;
 		return IIO_VAL_INT_PLUS_MICRO;
+
 	case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
 		*val = mcp9600_tc_types[data->thermocouple_type];
 		return IIO_VAL_CHAR;
+
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		*val = mcp_iir_coefficients_avail[data->filter_level];
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int mcp9600_read_avail(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      const int **vals, int *type, int *length,
+			      long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		*vals = mcp_iir_coefficients_avail;
+		*type = IIO_VAL_INT;
+		*length = ARRAY_SIZE(mcp_iir_coefficients_avail);
+		return IIO_AVAIL_LIST;
 	default:
 		return -EINVAL;
 	}
@@ -211,6 +243,7 @@ static int mcp9600_config(struct mcp9600_data *data)
 
 	cfg  = FIELD_PREP(MCP9600_SENSOR_TYPE_MASK,
 			  mcp9600_type_map[data->thermocouple_type]);
+	FIELD_MODIFY(MCP9600_FILTER_MASK, &cfg, data->filter_level);
 
 	ret = i2c_smbus_write_byte_data(client, MCP9600_SENSOR_CFG, cfg);
 	if (ret < 0) {
@@ -221,6 +254,43 @@ static int mcp9600_config(struct mcp9600_data *data)
 	return 0;
 }
 
+static int mcp9600_write_raw_get_fmt(struct iio_dev *indio_dev,
+				     struct iio_chan_spec const *chan,
+				     long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int mcp9600_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct mcp9600_data *data = iio_priv(indio_dev);
+	int i;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+		for (i = 0; i < ARRAY_SIZE(mcp_iir_coefficients_avail); i++) {
+			if (mcp_iir_coefficients_avail[i] == val)
+				break;
+		}
+
+		if (i == ARRAY_SIZE(mcp_iir_coefficients_avail))
+			return -EINVAL;
+
+		data->filter_level = i;
+		return mcp9600_config(data);
+
+	default:
+		return -EINVAL;
+	}
+}
+
 static int mcp9600_get_alert_index(int channel2, enum iio_event_direction dir)
 {
 	if (channel2 == IIO_MOD_TEMP_AMBIENT) {
@@ -358,6 +428,9 @@ static int mcp9600_write_thresh(struct iio_dev *indio_dev,
 
 static const struct iio_info mcp9600_info = {
 	.read_raw = mcp9600_read_raw,
+	.read_avail = mcp9600_read_avail,
+	.write_raw = mcp9600_write_raw,
+	.write_raw_get_fmt = mcp9600_write_raw_get_fmt,
 	.read_event_config = mcp9600_read_event_config,
 	.write_event_config = mcp9600_write_event_config,
 	.read_event_value = mcp9600_read_thresh,
-- 
2.50.1