linux-kernel - [PATCH v3 08/12] iio: accel: adxl313: add FIFO watermark

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Message-Id: <20250523223523.35218-9-l.rubusch@gmail.com>
Date: Fri, 23 May 2025 22:35:19 +0000
From: Lothar Rubusch <l.rubusch@...il.com>
To: jic23@...nel.org,
	dlechner@...libre.com,
	nuno.sa@...log.com,
	andy@...nel.org,
	corbet@....net,
	lucas.p.stankus@...il.com,
	lars@...afoo.de,
	Michael.Hennerich@...log.com
Cc: l.rubusch@...il.com,
	linux-iio@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 08/12] iio: accel: adxl313: add FIFO watermark

Add FIFO watermark configuration and evaluation. Let a watermark to be
configured. Evaluate the interrupt accordingly. Read out the FIFO content
and push the values to the IIO channel.

Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
---
 drivers/iio/accel/adxl313.h      |  1 +
 drivers/iio/accel/adxl313_core.c | 63 ++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index 9cdad55dd350..8c68cff7569c 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -87,6 +87,7 @@ struct adxl313_data {
 	const struct adxl313_chip_info *chip_info;
 	struct mutex	lock; /* lock to protect transf_buf */
 	int irq;
+	u8 watermark;
 	u8 fifo_mode;
 	__le16		transf_buf __aligned(IIO_DMA_MINALIGN);
 	__le16		fifo_buf[ADXL313_NUM_AXIS * ADXL313_FIFO_SIZE + 1];
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 1e085f0c61a0..80991cd9bd79 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -373,6 +373,25 @@ static int adxl313_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_set_watermark(struct iio_dev *indio_dev, unsigned int value)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	const unsigned int fifo_mask = 0x1f, interrupt_mask = 0x02;
+	int ret;
+
+	value = min(value, ADXL313_FIFO_SIZE - 1);
+
+	ret = regmap_update_bits(data->regmap, ADXL313_REG_FIFO_CTL,
+				 fifo_mask, value);
+	if (ret)
+		return ret;
+
+	data->watermark = value;
+
+	return regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
+				  interrupt_mask, ADXL313_INT_WATERMARK);
+}
+
 static int adxl313_get_samples(struct adxl313_data *data)
 {
 	unsigned int regval = 0;
@@ -399,6 +418,7 @@ static int adxl313_set_fifo(struct adxl313_data *data)
 		return ret;
 
 	ret = regmap_write(data->regmap, ADXL313_REG_FIFO_CTL,
+			   FIELD_PREP(ADXL313_REG_FIFO_CTL_SAMPLES_MSK,	data->watermark) |
 			   FIELD_PREP(ADXL313_REG_FIFO_CTL_MODE_MSK, data->fifo_mode));
 
 	return adxl313_set_measure_en(data, true);
@@ -471,6 +491,39 @@ static const struct iio_buffer_setup_ops adxl313_buffer_ops = {
 	.predisable = adxl313_buffer_predisable,
 };
 
+static int adxl313_fifo_push(struct iio_dev *indio_dev, int samples)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	unsigned int i;
+	int ret;
+
+	ret = adxl313_fifo_transfer(data, samples);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ADXL313_NUM_AXIS * samples; i += ADXL313_NUM_AXIS)
+		iio_push_to_buffers(indio_dev, &data->fifo_buf[i]);
+
+	return 0;
+}
+
+static int adxl313_push_event(struct iio_dev *indio_dev, int int_stat)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	int samples;
+
+	if (FIELD_GET(ADXL313_INT_WATERMARK, int_stat)) {
+		samples = adxl313_get_samples(data);
+		if (samples < 0)
+			return samples;
+
+		return adxl313_fifo_push(indio_dev, samples);
+	}
+
+	/* Return error if no event data was pushed to the IIO channel. */
+	return -ENOENT;
+}
+
 static irqreturn_t adxl313_irq_handler(int irq, void *p)
 {
 	struct iio_dev *indio_dev = p;
@@ -480,6 +533,15 @@ static irqreturn_t adxl313_irq_handler(int irq, void *p)
 	if (regmap_read(data->regmap, ADXL313_REG_INT_SOURCE, &int_stat))
 		return IRQ_NONE;
 
+	if (adxl313_push_event(indio_dev, int_stat))
+		goto err;
+
+	if (FIELD_GET(ADXL313_INT_OVERRUN, int_stat))
+		goto err;
+
+	return IRQ_HANDLED;
+
+err:
 	adxl313_fifo_reset(data);
 
 	return IRQ_HANDLED;
@@ -499,6 +561,7 @@ static const struct iio_info adxl313_info = {
 	.read_raw	= adxl313_read_raw,
 	.write_raw	= adxl313_write_raw,
 	.read_avail	= adxl313_read_freq_avail,
+	.hwfifo_set_watermark = adxl313_set_watermark,
 	.debugfs_reg_access = &adxl313_reg_access,
 };
 
-- 
2.39.5