[PATCH v4 4/4] iio: proximity: rfd77402: Add interrupt handling support
From: Shrikant Raskar via B4 Relay
Date: Thu Jan 01 2026 - 11:18:27 EST
From: Shrikant Raskar <raskar.shree97@xxxxxxxxx>
Add interrupt handling support to enable event-driven data acquisition
instead of continuous polling. This improves responsiveness, reduces
CPU overhead, and supports low-power operation by allowing the system
to remain idle until an interrupt occurs.
Signed-off-by: Shrikant Raskar <raskar.shree97@xxxxxxxxx>
---
drivers/iio/proximity/rfd77402.c | 136 ++++++++++++++++++++++++++++++++++-----
1 file changed, 120 insertions(+), 16 deletions(-)
diff --git a/drivers/iio/proximity/rfd77402.c b/drivers/iio/proximity/rfd77402.c
index 496c1412ebf8..8cddf509f9c6 100644
--- a/drivers/iio/proximity/rfd77402.c
+++ b/drivers/iio/proximity/rfd77402.c
@@ -6,13 +6,14 @@
*
* 7-bit I2C slave address 0x4c
*
- * TODO: interrupt
* https://media.digikey.com/pdf/Data%20Sheets/RF%20Digital%20PDFs/RFD77402.pdf
*/
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/completion.h>
#include <linux/iopoll.h>
#include <linux/iio/iio.h>
@@ -20,6 +21,8 @@
#define RFD77402_DRV_NAME "rfd77402"
#define RFD77402_ICSR 0x00 /* Interrupt Control Status Register */
+#define RFD77402_ICSR_CLR_CFG BIT(0)
+#define RFD77402_ICSR_CLR_TYPE BIT(1)
#define RFD77402_ICSR_INT_MODE BIT(2)
#define RFD77402_ICSR_INT_POL BIT(3)
#define RFD77402_ICSR_RESULT BIT(4)
@@ -27,6 +30,12 @@
#define RFD77402_ICSR_H2M_MSG BIT(6)
#define RFD77402_ICSR_RESET BIT(7)
+#define RFD77402_IER 0x02
+#define RFD77402_IER_RESULT BIT(0)
+#define RFD77402_IER_M2H_MSG BIT(1)
+#define RFD77402_IER_H2M_MSG BIT(2)
+#define RFD77402_IER_RESET BIT(3)
+
#define RFD77402_CMD_R 0x04
#define RFD77402_CMD_SINGLE 0x01
#define RFD77402_CMD_STANDBY 0x10
@@ -77,10 +86,18 @@ static const struct {
{RFD77402_HFCFG_3, 0x45d4},
};
+/**
+ * struct rfd77402_data - device-specific data for the RFD77402 sensor
+ * @client: I2C client handle
+ * @lock: mutex to serialize sensor reads
+ * @completion: completion used for interrupt-driven measurements
+ * @irq_en: indicates whether interrupt mode is enabled
+ */
struct rfd77402_data {
struct i2c_client *client;
- /* Serialize reads from the sensor */
struct mutex lock;
+ struct completion completion;
+ bool irq_en;
};
static const struct iio_chan_spec rfd77402_channels[] = {
@@ -91,6 +108,39 @@ static const struct iio_chan_spec rfd77402_channels[] = {
},
};
+static irqreturn_t rfd77402_interrupt_handler(int irq, void *pdata)
+{
+ struct rfd77402_data *data = pdata;
+ int ret;
+
+ if (!data || !data->client)
+ return IRQ_NONE;
+
+ ret = i2c_smbus_read_byte_data(data->client, RFD77402_ICSR);
+ if (ret < 0)
+ return IRQ_NONE;
+
+ /* Check if the interrupt is from our device */
+ if (!(ret & RFD77402_ICSR_RESULT))
+ return IRQ_NONE;
+
+ /* Signal completion of measurement */
+ complete(&data->completion);
+ return IRQ_HANDLED;
+}
+
+static int rfd77402_wait_for_irq(struct rfd77402_data *data)
+{
+ int ret;
+ /* As per datasheet, single measurement flow takes 100ms */
+ ret = wait_for_completion_timeout(&data->completion,
+ msecs_to_jiffies(100));
+ if (ret == 0)
+ return -ETIMEDOUT;
+
+ return 0;
+}
+
static int rfd77402_set_state(struct i2c_client *client, u8 state, u16 check)
{
int ret;
@@ -111,8 +161,9 @@ static int rfd77402_set_state(struct i2c_client *client, u8 state, u16 check)
return 0;
}
-static int rfd77402_measure(struct i2c_client *client)
+static int rfd77402_measure(struct rfd77402_data *data)
{
+ struct i2c_client *client = data->client;
int ret;
ret = rfd77402_set_state(client, RFD77402_CMD_MCPU_ON,
@@ -126,13 +177,19 @@ static int rfd77402_measure(struct i2c_client *client)
if (ret < 0)
goto err;
- /* Poll ICSR until RESULT bit is set */
- ret = read_poll_timeout(i2c_smbus_read_byte_data, ret,
- ret & RFD77402_ICSR_RESULT,
- 10000, /* sleep: 10ms */
- 100000, /* timeout: 100ms */
- false,
- client, RFD77402_ICSR);
+ if (data->irq_en) {
+ /* Re-initialize completion and wait for interrupt */
+ reinit_completion(&data->completion);
+ ret = rfd77402_wait_for_irq(data);
+ } else {
+ /* Poll ICSR until RESULT bit is set */
+ ret = read_poll_timeout(i2c_smbus_read_byte_data, ret,
+ ret & RFD77402_ICSR_RESULT,
+ 10000, /* sleep 10ms */
+ 100000, /* timeout 100ms */
+ false,
+ client, RFD77402_ICSR);
+ }
if (ret < 0)
goto err;
@@ -164,7 +221,7 @@ static int rfd77402_read_raw(struct iio_dev *indio_dev,
switch (mask) {
case IIO_CHAN_INFO_RAW:
mutex_lock(&data->lock);
- ret = rfd77402_measure(data->client);
+ ret = rfd77402_measure(data);
mutex_unlock(&data->lock);
if (ret < 0)
return ret;
@@ -184,8 +241,21 @@ static const struct iio_info rfd77402_info = {
.read_raw = rfd77402_read_raw,
};
+static int rfd77402_config_irq(struct i2c_client *client, u8 csr, u8 ier)
+{
+ int ret;
+
+ ret = i2c_smbus_write_byte_data(client, RFD77402_ICSR, csr);
+ if (ret)
+ return ret;
+
+ return i2c_smbus_write_byte_data(client, RFD77402_IER, ier);
+}
+
static int rfd77402_init(struct i2c_client *client)
{
+ struct iio_dev *indio_dev = i2c_get_clientdata(client);
+ struct rfd77402_data *data = iio_priv(indio_dev);
int ret, i;
ret = rfd77402_set_state(client, RFD77402_CMD_STANDBY,
@@ -193,10 +263,24 @@ static int rfd77402_init(struct i2c_client *client)
if (ret < 0)
return ret;
- /* configure INT pad as push-pull, active low */
- ret = i2c_smbus_write_byte_data(client, RFD77402_ICSR,
- RFD77402_ICSR_INT_MODE);
- if (ret < 0)
+ if (data->irq_en) {
+ /* Enable interrupt mode:
+ * - Configure ICSR for auto-clear on read and
+ * push-pull output
+ * - Enable "result ready" interrupt in IER
+ */
+ ret = rfd77402_config_irq(client,
+ RFD77402_ICSR_CLR_CFG |
+ RFD77402_ICSR_INT_MODE,
+ RFD77402_IER_RESULT);
+ } else {
+ /* Disable all interrupts:
+ * - Clear ICSR configuration
+ * - Disable all interrupts in IER
+ */
+ ret = rfd77402_config_irq(client, 0, 0);
+ }
+ if (ret)
return ret;
/* I2C configuration */
@@ -271,7 +355,27 @@ static int rfd77402_probe(struct i2c_client *client)
data = iio_priv(indio_dev);
data->client = client;
- mutex_init(&data->lock);
+ ret = devm_mutex_init(&client->dev, &data->lock);
+ if (ret)
+ return ret;
+
+ init_completion(&data->completion);
+ i2c_set_clientdata(client, indio_dev);
+
+ data->irq_en = false;
+ if (client->irq > 0) {
+ ret = devm_request_threaded_irq(&client->dev, client->irq,
+ NULL, rfd77402_interrupt_handler,
+ IRQF_ONESHOT,
+ "rfd77402", data);
+ if (ret)
+ return ret;
+
+ data->irq_en = true;
+ dev_dbg(&client->dev, "Using interrupt mode\n");
+ } else {
+ dev_dbg(&client->dev, "Using polling mode\n");
+ }
indio_dev->info = &rfd77402_info;
indio_dev->channels = rfd77402_channels;
--
2.43.0