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Message-ID: <f8e95533-c486-442f-a186-5e746dad2f4c@baylibre.com>
Date: Tue, 19 Aug 2025 09:05:39 -0500
From: David Lechner <dlechner@...libre.com>
To: Ben Collins <bcollins@...nel.org>, Jonathan Cameron <jic23@...nel.org>,
Nuno Sá <nuno.sa@...log.com>,
Andy Shevchenko <andy@...nel.org>
Cc: Ben Collins <bcollins@...ter.com>, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] iio: mcp9600: Add support for IIR filter
On 8/18/25 1:32 PM, Ben Collins wrote:
> From: Ben Collins <bcollins@...ter.com>
>
> MCP9600 supports an IIR filter with 7 levels. Add IIR attribute
> to allow get/set of this value.
>
> Use a filter_type[none, ema] for enabling the IIR filter.
>
> Signed-off-by: Ben Collins <bcollins@...ter.com>
> ---
> drivers/iio/temperature/mcp9600.c | 157 ++++++++++++++++++++++++++++++
> 1 file changed, 157 insertions(+)
>
> diff --git a/drivers/iio/temperature/mcp9600.c b/drivers/iio/temperature/mcp9600.c
> index 9b017820efc1..0ec47cbeb88c 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 +95,27 @@ static const int mcp9600_tc_types[] = {
> [THERMOCOUPLE_TYPE_R] = 'R',
> };
>
> +enum mcp9600_filter {
> + MCP9600_FILTER_TYPE_NONE,
> + MCP9600_FILTER_TYPE_EMA,
> +};
> +
> +static const char * const mcp9600_filter_type[] = {
> + [MCP9600_FILTER_TYPE_NONE] = "none",
> + [MCP9600_FILTER_TYPE_EMA] = "ema",
> +};
> +
> +static const int mcp_iir_coefficients_avail[7][2] = {
> + /* Level 0 is no filter */
> + { 0, 524549 },
> + { 0, 243901 },
> + { 0, 119994 },
> + { 0, 59761 },
> + { 0, 29851 },
> + { 0, 14922 },
> + { 0, 7461 },
> +};
> +
> static const struct iio_event_spec mcp9600_events[] = {
> {
> .type = IIO_EV_TYPE_THRESH,
> @@ -118,7 +140,11 @@ 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), \
> + .ext_info = mcp9600_ext_filter, \
> .event_spec = &mcp9600_events[hj_ev_spec_off], \
> .num_event_specs = hj_num_ev, \
> }, \
> @@ -134,6 +160,26 @@ static const struct iio_event_spec mcp9600_events[] = {
> }, \
> }
>
> +static int mcp9600_get_filter(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan);
> +static int mcp9600_set_filter(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + unsigned int mode);
> +
> +static const struct iio_enum mcp9600_filter_enum = {
> + .items = mcp9600_filter_type,
> + .num_items = ARRAY_SIZE(mcp9600_filter_type),
> + .get = mcp9600_get_filter,
> + .set = mcp9600_set_filter,
> +};
> +
> +static const struct iio_chan_spec_ext_info mcp9600_ext_filter[] = {
> + IIO_ENUM("filter_type", IIO_SHARED_BY_ALL, &mcp9600_filter_enum),
> + IIO_ENUM_AVAILABLE("filter_type", IIO_SHARED_BY_ALL,
> + &mcp9600_filter_enum),
> + { }
> +};
> +
> static const struct iio_chan_spec mcp9600_channels[][2] = {
> MCP9600_CHANNELS(0, 0, 0, 0), /* Alerts: - - - - */
> MCP9600_CHANNELS(1, 0, 0, 0), /* Alerts: 1 - - - */
> @@ -161,6 +207,8 @@ struct mcp_chip_info {
> struct mcp9600_data {
> struct i2c_client *client;
> u32 thermocouple_type;
> + /* Filter enabled is 1-7, with 0 being off (filter_type none) */
> + u8 filter_level;
> };
>
> static int mcp9600_read(struct mcp9600_data *data,
> @@ -191,13 +239,45 @@ 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:
> + if (data->filter_level == 0)
> + return -EINVAL;
To implement Jonathan's request from v5, drop this error return.
We'll also need a separate bool data->is_filter_enabled field so
that we can keep the last set filter_level even when the filter
is disabled. (i.e. data->filter_level is never == 0).
This way, if you set the filter level, you can enable and disable
the filter via filter_type and still have the same filter level.
> +
> + *val = mcp_iir_coefficients_avail[data->filter_level - 1][0];
> + *val2 = mcp_iir_coefficients_avail[data->filter_level - 1][1];
> + return IIO_VAL_INT_PLUS_MICRO;
> +
> + 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)
> +{
> + struct mcp9600_data *data = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> + if (data->filter_level == 0)
> + return -EINVAL;
> +
> + *vals = (int *)mcp_iir_coefficients_avail;
> + *type = IIO_VAL_INT_PLUS_MICRO;
> + *length = 2 * ARRAY_SIZE(mcp_iir_coefficients_avail);
> + return IIO_AVAIL_LIST;
> default:
> return -EINVAL;
> }
> @@ -211,6 +291,7 @@ 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);
And change the logic here to:
FIELD_MODIFY(MCP9600_FILTER_MASK, &cfg, data->is_filter_enabled ?
data->filter_level : 0);
>
> ret = i2c_smbus_write_byte_data(client, MCP9600_SENSOR_CFG, cfg);
> if (ret < 0) {
> @@ -221,6 +302,79 @@ 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_PLUS_MICRO;
> + 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][0] == val &&
> + mcp_iir_coefficients_avail[i][1] == val2)
> + break;
> + }
> +
> + if (i == ARRAY_SIZE(mcp_iir_coefficients_avail))
> + return -EINVAL;
> +
> + data->filter_level = i + 1;
> + return mcp9600_config(data);
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int mcp9600_get_filter(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan)
> +{
> + struct mcp9600_data *data = iio_priv(indio_dev);
> +
> + if (data->filter_level == 0)
> + return MCP9600_FILTER_TYPE_NONE;
> +
> + return MCP9600_FILTER_TYPE_EMA;
> +}
> +
> +static int mcp9600_set_filter(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + unsigned int mode)
> +{
> + struct mcp9600_data *data = iio_priv(indio_dev);
> +
> + switch (mode) {
> + case MCP9600_FILTER_TYPE_NONE:
> + data->filter_level = 0;
Don't touch data->filter_level here, just set data->is_filter_enabled = false.
> + return mcp9600_config(data);
> +
> + case MCP9600_FILTER_TYPE_EMA:
> + if (data->filter_level == 0) {
> + /* Minimum filter by default */
> + data->filter_level = 1;
And similar, just set data->is_filter_enabled = true without changing filter_level.
> + return mcp9600_config(data);
> + }
> + return 0;
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> static int mcp9600_get_alert_index(int channel2, enum iio_event_direction dir)
> {
> if (channel2 == IIO_MOD_TEMP_AMBIENT) {
> @@ -358,6 +512,9 @@ 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,
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