Prepare the interrupt handler. Add register entries to evaluate the
incoming interrupt. Add functions to clear status registers and reset the
FIFO.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  16 ++++
 drivers/iio/accel/adxl313_core.c | 131 +++++++++++++++++++++++++++++++
 2 files changed, 147 insertions(+)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index c5673f1934fb..4cb1fe1f2616 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -49,11 +49,25 @@
 #define ADXL313_SPI_3WIRE		BIT(6)
 #define ADXL313_I2C_DISABLE		BIT(6)
 
+#define ADXL313_INT_OVERRUN		BIT(0)
+#define ADXL313_INT_WATERMARK		BIT(1)
+#define ADXL313_INT_INACTIVITY		BIT(3)
+#define ADXL313_INT_ACTIVITY		BIT(4)
+#define ADXL313_INT_DREADY		BIT(7)
+
+/* FIFO entries: how many values are stored in the FIFO */
+#define ADXL313_REG_FIFO_STATUS_ENTRIES_MSK	GENMASK(5, 0)
+/* FIFO samples: number of samples needed for watermark (FIFO mode) */
+#define ADXL313_REG_FIFO_CTL_SAMPLES_MSK	GENMASK(4, 0)
 #define ADXL313_REG_FIFO_CTL_MODE_MSK		GENMASK(7, 6)
 
 #define ADXL313_FIFO_BYPASS			0
 #define ADXL313_FIFO_STREAM			2
 
+#define ADXL313_FIFO_SIZE			32
+
+#define ADXL313_NUM_AXIS			3
+
 extern const struct regmap_access_table adxl312_readable_regs_table;
 extern const struct regmap_access_table adxl313_readable_regs_table;
 extern const struct regmap_access_table adxl314_readable_regs_table;
@@ -75,7 +89,9 @@ struct adxl313_data {
 	const struct adxl313_chip_info *chip_info;
 	struct mutex	lock; /* lock to protect transf_buf */
 	int irq;
+	u8 fifo_mode;
 	__le16		transf_buf __aligned(IIO_DMA_MINALIGN);
+	__le16		fifo_buf[ADXL313_NUM_AXIS * ADXL313_FIFO_SIZE + 1];
 };
 
 struct adxl313_chip_info {
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 52fb10680939..8eecd2851512 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -13,12 +13,20 @@
 #include <linux/property.h>
 #include <linux/regmap.h>
 
+#include <linux/iio/buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/sysfs.h>
+
 #include "adxl313.h"
 
 #define ADXL313_INT_NONE			U8_MAX
 #define ADXL313_INT1				1
 #define ADXL313_INT2				2
 
+#define ADXL313_REG_XYZ_BASE			ADXL313_REG_DATA_AXIS(0)
+
 static const struct regmap_range adxl312_readable_reg_range[] = {
 	regmap_reg_range(ADXL313_REG_DEVID0, ADXL313_REG_DEVID0),
 	regmap_reg_range(ADXL313_REG_OFS_AXIS(0), ADXL313_REG_OFS_AXIS(2)),
@@ -62,6 +70,7 @@ bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg)
 	case ADXL313_REG_DATA_AXIS(4):
 	case ADXL313_REG_DATA_AXIS(5):
 	case ADXL313_REG_FIFO_STATUS:
+	case ADXL313_REG_INT_SOURCE:
 		return true;
 	default:
 		return false;
@@ -365,6 +374,116 @@ static int adxl313_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_get_samples(struct adxl313_data *data)
+{
+	unsigned int regval = 0;
+	int ret;
+
+	ret = regmap_read(data->regmap, ADXL313_REG_FIFO_STATUS, &regval);
+	if (ret)
+		return ret;
+
+	return FIELD_GET(ADXL313_REG_FIFO_STATUS_ENTRIES_MSK, regval);
+}
+
+static int adxl313_set_fifo(struct adxl313_data *data)
+{
+	unsigned int int_line;
+	int ret;
+
+	ret = adxl313_set_measure_en(data, false);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(data->regmap, ADXL313_REG_INT_MAP, &int_line);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(data->regmap, ADXL313_REG_FIFO_CTL,
+			   FIELD_PREP(ADXL313_REG_FIFO_CTL_MODE_MSK, data->fifo_mode));
+
+	return adxl313_set_measure_en(data, true);
+}
+
+static int adxl313_fifo_transfer(struct adxl313_data *data, int samples)
+{
+	size_t count;
+	int i;
+	int ret;
+
+	count = sizeof(data->fifo_buf[0]) * ADXL313_NUM_AXIS;
+	for (i = 0; i < samples; i++) {
+		ret = regmap_bulk_read(data->regmap, ADXL313_REG_XYZ_BASE,
+				       data->fifo_buf + (i * count / 2), count);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void adxl313_fifo_reset(struct adxl313_data *data)
+{
+	int regval;
+	int samples;
+
+	adxl313_set_measure_en(data, false);
+
+	/* clear samples */
+	samples = adxl313_get_samples(data);
+	if (samples)
+		adxl313_fifo_transfer(data, samples);
+
+	/* clear interrupt register */
+	regmap_read(data->regmap, ADXL313_REG_INT_SOURCE, &regval);
+
+	adxl313_set_measure_en(data, true);
+}
+
+static int adxl313_buffer_postenable(struct iio_dev *indio_dev)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+
+	data->fifo_mode = ADXL313_FIFO_STREAM;
+	return adxl313_set_fifo(data);
+}
+
+static int adxl313_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	int ret;
+
+	data->fifo_mode = ADXL313_FIFO_BYPASS;
+	ret = adxl313_set_fifo(data);
+	if (ret)
+		return ret;
+
+	return regmap_write(data->regmap, ADXL313_REG_INT_ENABLE, 0);
+}
+
+static const struct iio_buffer_setup_ops adxl313_buffer_ops = {
+	.postenable = adxl313_buffer_postenable,
+	.predisable = adxl313_buffer_predisable,
+};
+
+static irqreturn_t adxl313_irq_handler(int irq, void *p)
+{
+	struct iio_dev *indio_dev = p;
+	struct adxl313_data *data = iio_priv(indio_dev);
+	int int_stat;
+
+	if (regmap_read(data->regmap, ADXL313_REG_INT_SOURCE, &int_stat))
+		return IRQ_NONE;
+
+	if (FIELD_GET(ADXL313_INT_OVERRUN, int_stat))
+		goto err;
+
+	return IRQ_HANDLED;
+err:
+	adxl313_fifo_reset(data);
+
+	return IRQ_HANDLED;
+}
+
 static int adxl313_reg_access(struct iio_dev *indio_dev, unsigned int reg,
 			      unsigned int writeval, unsigned int *readval)
 {
@@ -486,6 +605,18 @@ int adxl313_core_probe(struct device *dev,
 		ret = regmap_write(data->regmap, ADXL313_REG_INT_MAP, regval);
 		if (ret)
 			return ret;
+
+		ret  = devm_iio_kfifo_buffer_setup(dev, indio_dev,
+						   &adxl313_buffer_ops);
+		if (ret)
+			return ret;
+
+		ret = devm_request_threaded_irq(dev, data->irq, NULL,
+						&adxl313_irq_handler,
+						IRQF_SHARED | IRQF_ONESHOT,
+						indio_dev->name, indio_dev);
+		if (ret)
+			return ret;
 	} else {
 		/* FIFO_BYPASSED mode */
 		ret = regmap_write(data->regmap, ADXL313_REG_FIFO_CTL,
-- 
2.39.5

On Tue, May 20, 2025 at 10:50:02PM +0000, Lothar Rubusch wrote:
> Prepare the interrupt handler. Add register entries to evaluate the
> incoming interrupt. Add functions to clear status registers and reset the
> FIFO.

...

> +static int adxl313_fifo_transfer(struct adxl313_data *data, int samples)
> +{
> +	size_t count;

> +	int i;

Does it need to be signed?

> +	int ret;
> +
> +	count = sizeof(data->fifo_buf[0]) * ADXL313_NUM_AXIS;
> +	for (i = 0; i < samples; i++) {
> +		ret = regmap_bulk_read(data->regmap, ADXL313_REG_XYZ_BASE,
> +				       data->fifo_buf + (i * count / 2), count);
> +		if (ret)
> +			return ret;
> +	}
> +	return 0;
> +}

...

> +static void adxl313_fifo_reset(struct adxl313_data *data)
> +{
> +	int regval;

Incorrect type. Please, go through your whole code and check that for regmap
returned value you use the same type. Using signed might lead to subtle and
hard-to-hunt mistakes due to integer promotion rules in C language.

> +	int samples;
> +
> +	adxl313_set_measure_en(data, false);
> +
> +	/* clear samples */
> +	samples = adxl313_get_samples(data);
> +	if (samples)
> +		adxl313_fifo_transfer(data, samples);
> +
> +	/* clear interrupt register */
> +	regmap_read(data->regmap, ADXL313_REG_INT_SOURCE, &regval);

No error check? At least comment why it's okay to go like this.

> +	adxl313_set_measure_en(data, true);
> +}

...

> +static irqreturn_t adxl313_irq_handler(int irq, void *p)
> +{
> +	struct iio_dev *indio_dev = p;
> +	struct adxl313_data *data = iio_priv(indio_dev);
> +	int int_stat;
> +
> +	if (regmap_read(data->regmap, ADXL313_REG_INT_SOURCE, &int_stat))
> +		return IRQ_NONE;
> +
> +	if (FIELD_GET(ADXL313_INT_OVERRUN, int_stat))
> +		goto err;
> +
> +	return IRQ_HANDLED;

> +err:
> +	adxl313_fifo_reset(data);
> +
> +	return IRQ_HANDLED;

Seems you ignored my comment in previous review round. Please, re-read that
thread and discuss all the stuff you disagree with (I want to know why).

> +}

...

> +		ret  = devm_iio_kfifo_buffer_setup(dev, indio_dev,

One space too many.

> +						   &adxl313_buffer_ops);
> +		if (ret)
> +			return ret;

-- 
With Best Regards,
Andy Shevchenko