iio: proximity: rfd77402: Add interrupt handling support

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.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Shrikant Raskar <raskar.shree97@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: embedded-essentials

drivers/iio/proximity/rfd77402.c

@@ -6,27 +6,41 @@
  *
  * 7-bit I2C slave address 0x4c
  *
- * TODO: interrupt
  * https://media.digikey.com/pdf/Data%20Sheets/RF%20Digital%20PDFs/RFD77402.pdf
  */
 
+#include <linux/bits.h>
+#include <linux/completion.h>
 #include <linux/delay.h>
+#include <linux/dev_printk.h>
+#include <linux/errno.h>
 #include <linux/i2c.h>
+#include <linux/interrupt.h>
 #include <linux/iopoll.h>
+#include <linux/jiffies.h>
 #include <linux/module.h>
+#include <linux/types.h>
 
 #include <linux/iio/iio.h>
 
 #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)
 #define RFD77402_ICSR_M2H_MSG	BIT(5)
 #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
@@ -81,10 +95,14 @@ static const struct {
  * 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;
 	struct mutex lock;
+	struct completion completion;
+	bool irq_en;
 };
 
 static const struct iio_chan_spec rfd77402_channels[] = {
@@ -95,6 +113,41 @@ 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;
+
+	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;
+
+	/*
+	 * According to RFD77402 Datasheet v1.8,
+	 * Section 3.1.1 "Single Measure" (Figure: Single Measure Flow Chart),
+	 * the suggested timeout for single measure is 100 ms.
+	 */
+	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;
@@ -120,6 +173,11 @@ static int rfd77402_wait_for_result(struct rfd77402_data *data)
 	struct i2c_client *client = data->client;
 	int val, ret;
 
+	if (data->irq_en) {
+		reinit_completion(&data->completion);
+		return rfd77402_wait_for_irq(data);
+	}
+
 	/*
 	 * As per RFD77402 datasheet section '3.1.1 Single Measure', the
 	 * suggested timeout value for single measure is 100ms.
@@ -204,19 +262,47 @@ static const struct iio_info rfd77402_info = {
 	.read_raw = rfd77402_read_raw,
 };
 
-static int rfd77402_init(struct i2c_client *client)
+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 rfd77402_data *data)
+{
+	struct i2c_client *client = data->client;
 	int ret, i;
 
 	ret = rfd77402_set_state(client, RFD77402_CMD_STANDBY,
 				 RFD77402_STATUS_STANDBY);
 	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 */
@@ -296,13 +382,29 @@ static int rfd77402_probe(struct i2c_client *client)
 	if (ret)
 		return ret;
 
+	init_completion(&data->completion);
+
+	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;
 	indio_dev->num_channels = ARRAY_SIZE(rfd77402_channels);
 	indio_dev->name = RFD77402_DRV_NAME;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
-	ret = rfd77402_init(client);
+	ret = rfd77402_init(data);
 	if (ret < 0)
 		return ret;
 
@@ -320,7 +422,10 @@ static int rfd77402_suspend(struct device *dev)
 
 static int rfd77402_resume(struct device *dev)
 {
-	return rfd77402_init(to_i2c_client(dev));
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct rfd77402_data *data = iio_priv(indio_dev);
+
+	return rfd77402_init(data);
 }
 
 static DEFINE_SIMPLE_DEV_PM_OPS(rfd77402_pm_ops, rfd77402_suspend,