[PATCH v4 4/5] iio: adc: ad7380: add alert support

Julien Stephan
2025-01-08T12:49:47Z

The alert functionality is an out of range indicator and can be used as
an early indicator of an out of bounds conversion result.

ALERT_LOW_THRESHOLD and ALERT_HIGH_THRESHOLD registers are common to all
channels.

When using 1 SDO line (only mode supported by the driver right now), i.e
data outputs only on SDOA, SDOB (or SDOD for 4 channels variants) is
used as an alert pin. The alert pin is updated at the end of the
conversion (set to low if an alert occurs) and is cleared on a falling
edge of CS.

The ALERT register contains information about the exact alert status:
channel and direction. ALERT register can be accessed using debugfs if
enabled.

User can set high/low thresholds and enable alert detection using the
regular iio events attributes:

events/in_thresh_falling_value events/in_thresh_rising_value
events/thresh_either_en

In most use cases, user will hardwire the alert pin to trigger a shutdown.

In theory, we could generate userspace IIO events for alerts, but this
is not implemented yet for several reasons [1]. This can be implemented
later if a real use case actually requires it.

Signed-off-by: Julien Stephan <jstephan@baylibre.com>

[1] https://lore.kernel.org/all/4be16272-5197-4fa1-918c-c4cdfcaee02e@baylibre.com/
---
drivers/iio/adc/ad7380.c | 197 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 197 insertions(+)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index a532de4422082df8503454d66fc49f75b52cff68..cedd45556ee38b3197f8dd7edea162c3f4ba1563 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -34,6 +34,7 @@
#include <linux/util_macros.h>

#include <linux/iio/buffer.h>
+#include <linux/iio/events.h>
#include <linux/iio/iio.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
@@ -112,6 +113,24 @@ struct ad7380_chip_info {
const struct ad7380_timing_specs *timing_specs;
};

+static const struct iio_event_spec ad7380_events[] = {
+ {
+ .type = IIO_EV_TYPE_THRESH,
+ .dir = IIO_EV_DIR_RISING,
+ .mask_shared_by_dir = BIT(IIO_EV_INFO_VALUE),
+ },
+ {
+ .type = IIO_EV_TYPE_THRESH,
+ .dir = IIO_EV_DIR_FALLING,
+ .mask_shared_by_dir = BIT(IIO_EV_INFO_VALUE),
+ },
+ {
+ .type = IIO_EV_TYPE_THRESH,
+ .dir = IIO_EV_DIR_EITHER,
+ .mask_shared_by_all = BIT(IIO_EV_INFO_ENABLE),
+ },
+};
+
enum {
AD7380_SCAN_TYPE_NORMAL,
AD7380_SCAN_TYPE_RESOLUTION_BOOST,
@@ -214,6 +233,8 @@ static const struct iio_scan_type ad7380_scan_type_16_u[] = {
.has_ext_scan_type = 1, \
.ext_scan_type = ad7380_scan_type_##bits##_##sign, \
.num_ext_scan_type = ARRAY_SIZE(ad7380_scan_type_##bits##_##sign), \
+ .event_spec = ad7380_events, \
+ .num_event_specs = ARRAY_SIZE(ad7380_events), \
}

#define AD7380_CHANNEL(index, bits, diff, sign) \
@@ -1157,12 +1178,188 @@ static int ad7380_get_current_scan_type(const struct iio_dev *indio_dev,
: AD7380_SCAN_TYPE_NORMAL;
}

+static int ad7380_read_event_config(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir)
+{
+ struct ad7380_state *st = iio_priv(indio_dev);
+ int tmp, ret;
+
+ ret = iio_device_claim_direct_mode(indio_dev);
+ if (ret)
+ return ret;
+
+ ret = regmap_read(st->regmap, AD7380_REG_ADDR_CONFIG1, &tmp);
+
+ iio_device_release_direct_mode(indio_dev);
+
+ if (ret)
+ return ret;
+
+ return FIELD_GET(AD7380_CONFIG1_ALERTEN, tmp);
+}
+
+static int ad7380_write_event_config(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ bool state)
+{
+ struct ad7380_state *st = iio_priv(indio_dev);
+ int ret;
+
+ ret = iio_device_claim_direct_mode(indio_dev);
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(st->regmap,
+ AD7380_REG_ADDR_CONFIG1,
+ AD7380_CONFIG1_ALERTEN,
+ FIELD_PREP(AD7380_CONFIG1_ALERTEN, state));
+
+ iio_device_release_direct_mode(indio_dev);
+
+ return ret;
+}
+
+static int ad7380_get_alert_th(struct ad7380_state *st,
+ enum iio_event_direction dir,
+ int *val)
+{
+ int ret, tmp;
+
+ switch (dir) {
+ case IIO_EV_DIR_RISING:
+ ret = regmap_read(st->regmap,
+ AD7380_REG_ADDR_ALERT_HIGH_TH,
+ &tmp);
+ if (ret)
+ return ret;
+
+ *val = FIELD_GET(AD7380_ALERT_HIGH_TH, tmp);
+ ret = IIO_VAL_INT;
+ break;
+ case IIO_EV_DIR_FALLING:
+ ret = regmap_read(st->regmap,
+ AD7380_REG_ADDR_ALERT_LOW_TH,
+ &tmp);
+ if (ret)
+ return ret;
+
+ *val = FIELD_GET(AD7380_ALERT_LOW_TH, tmp);
+ ret = IIO_VAL_INT;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+static int ad7380_read_event_value(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ enum iio_event_info info,
+ int *val, int *val2)
+{
+ struct ad7380_state *st = iio_priv(indio_dev);
+ int ret;
+
+ switch (info) {
+ case IIO_EV_INFO_VALUE:
+ ret = iio_device_claim_direct_mode(indio_dev);
+ if (ret)
+ return ret;
+
+ ret = ad7380_get_alert_th(st, dir, val);
+
+ iio_device_release_direct_mode(indio_dev);
+ return ret;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad7380_set_alert_th(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_direction dir,
+ int val)
+{
+ struct ad7380_state *st = iio_priv(indio_dev);
+ const struct iio_scan_type *scan_type;
+ u16 th;
+
+ /*
+ * According to the datasheet,
+ * AD7380_REG_ADDR_ALERT_HIGH_TH[11:0] are the 12 MSB of the
+ * 16-bits internal alert high register. LSB are set to 0xf.
+ * AD7380_REG_ADDR_ALERT_LOW_TH[11:0] are the 12 MSB of the
+ * 16 bits internal alert low register. LSB are set to 0x0.
+ *
+ * When alert is enabled the conversion from the adc is compared
+ * immediately to the alert high/low thresholds, before any
+ * oversampling. This means that the thresholds are the same for
+ * normal mode and oversampling mode.
+ */
+
+ /* Extract the 12 MSB of val */
+ scan_type = iio_get_current_scan_type(indio_dev, chan);
+ if (IS_ERR(scan_type))
+ return PTR_ERR(scan_type);
+
+ th = val >> (scan_type->realbits - 12);
+
+ switch (dir) {
+ case IIO_EV_DIR_RISING:
+ return regmap_write(st->regmap,
+ AD7380_REG_ADDR_ALERT_HIGH_TH,
+ th);
+ case IIO_EV_DIR_FALLING:
+ return regmap_write(st->regmap,
+ AD7380_REG_ADDR_ALERT_LOW_TH,
+ th);
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad7380_write_event_value(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ enum iio_event_info info,
+ int val, int val2)
+{
+ int ret;
+
+ switch (info) {
+ case IIO_EV_INFO_VALUE:
+ ret = iio_device_claim_direct_mode(indio_dev);
+ if (ret)
+ return ret;
+
+ ret = ad7380_set_alert_th(indio_dev, chan, dir, val);
+
+ iio_device_release_direct_mode(indio_dev);
+ return ret;
+ default:
+ return -EINVAL;
+ }
+}
+
static const struct iio_info ad7380_info = {
.read_raw = &ad7380_read_raw,
.read_avail = &ad7380_read_avail,
.write_raw = &ad7380_write_raw,
.get_current_scan_type = &ad7380_get_current_scan_type,
.debugfs_reg_access = &ad7380_debugfs_reg_access,
+ .read_event_config = &ad7380_read_event_config,
+ .write_event_config = &ad7380_write_event_config,
+ .read_event_value = &ad7380_read_event_value,
+ .write_event_value = &ad7380_write_event_value,
};

static int ad7380_init(struct ad7380_state *st, bool external_ref_en)

--
2.47.1