[PATCH v2 00/12] iio: accel: adxl313: add power-save on activity/inactivity

[PATCH v2 00/12] iio: accel: adxl313: add power-save on activity/inactivity

[Lothar Rubusch]

The patch set covers the following topics:
- add debug register and regmap cache
- prepare iio channel scan_type and scan_index
- prepare interrupt handling
- implement fifo with watermark
- add activity/inactivity together with auto-sleep with link bit
- documentation

Similar situation and approach as for the ADXL345. AC/DC coupling might be
a pending option as it is quite the same as for ADXL345.

Since activity and inactivity here are implemented covering all axis, I
assumed x&y&z. Thus the driver uses a fake channel for activity/inactiviy.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
v1 -> v2:
- usage of units.h
- simplify approach for return values
---
Lothar Rubusch (12):
  iio: accel: adxl313: add debug register
  iio: accel: adxl313: introduce channel scan_index
  iio: accel: adxl313: configure scan type for buffer
  iio: accel: adxl313: make use of regmap cache
  iio: accel: adxl313: add function to enable measurement
  iio: accel: adxl313: prepare interrupt handling
  iio: accel: adxl313: add basic interrupt handling
  iio: accel: adxl313: add FIFO watermark
  iio: accel: adxl313: add activity sensing
  iio: accel: adxl313: add inactivity sensing
  iio: accel: adxl313: implement power-save on inactivity
  docs: iio: add ADXL313 accelerometer

 Documentation/iio/adxl313.rst    | 196 ++++++++++
 Documentation/iio/index.rst      |   1 +
 drivers/iio/accel/adxl313.h      |  35 +-
 drivers/iio/accel/adxl313_core.c | 625 ++++++++++++++++++++++++++++++-
 drivers/iio/accel/adxl313_i2c.c  |   6 +
 drivers/iio/accel/adxl313_spi.c  |   6 +
 6 files changed, 860 insertions(+), 9 deletions(-)
 create mode 100644 Documentation/iio/adxl313.rst

-- 
2.39.5

[PATCH v2 01/12] iio: accel: adxl313: add debug register

[Lothar Rubusch]

Add iio debug register for general sensor debugging.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313_core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 4de0a41bd679..2f26da5857d4 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -321,10 +321,21 @@ static int adxl313_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_reg_access(struct iio_dev *indio_dev, unsigned int reg,
+			      unsigned int writeval, unsigned int *readval)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+
+	if (readval)
+		return regmap_read(data->regmap, reg, readval);
+	return regmap_write(data->regmap, reg, writeval);
+}
+
 static const struct iio_info adxl313_info = {
 	.read_raw	= adxl313_read_raw,
 	.write_raw	= adxl313_write_raw,
 	.read_avail	= adxl313_read_freq_avail,
+	.debugfs_reg_access = &adxl313_reg_access,
 };
 
 static int adxl313_setup(struct device *dev, struct adxl313_data *data,
-- 
2.39.5

[PATCH v2 02/12] iio: accel: adxl313: introduce channel scan_index

[Lothar Rubusch]

Add a scan_mask and scan_index to the iio channel. The scan_index
prepares the buffer usage.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313_core.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 2f26da5857d4..9c2f3af1d19f 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -171,9 +171,10 @@ static const int adxl313_odr_freqs[][2] = {
 	[9] = { 3200, 0 },
 };
 
-#define ADXL313_ACCEL_CHANNEL(index, axis) {				\
+#define ADXL313_ACCEL_CHANNEL(index, reg, axis) {			\
 	.type = IIO_ACCEL,						\
-	.address = index,						\
+	.scan_index = (index),						\
+	.address = (reg),						\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##axis,					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
@@ -187,10 +188,19 @@ static const int adxl313_odr_freqs[][2] = {
 	},								\
 }
 
+enum adxl313_chans {
+	chan_x, chan_y, chan_z,
+};
+
 static const struct iio_chan_spec adxl313_channels[] = {
-	ADXL313_ACCEL_CHANNEL(0, X),
-	ADXL313_ACCEL_CHANNEL(1, Y),
-	ADXL313_ACCEL_CHANNEL(2, Z),
+	ADXL313_ACCEL_CHANNEL(0, chan_x, X),
+	ADXL313_ACCEL_CHANNEL(1, chan_y, Y),
+	ADXL313_ACCEL_CHANNEL(2, chan_z, Z),
+};
+
+static const unsigned long adxl313_scan_masks[] = {
+	BIT(chan_x) | BIT(chan_y) | BIT(chan_z),
+	0
 };
 
 static int adxl313_set_odr(struct adxl313_data *data,
@@ -419,6 +429,7 @@ int adxl313_core_probe(struct device *dev,
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = adxl313_channels;
 	indio_dev->num_channels = ARRAY_SIZE(adxl313_channels);
+	indio_dev->available_scan_masks = adxl313_scan_masks;
 
 	ret = adxl313_setup(dev, data, setup);
 	if (ret) {
-- 
2.39.5

[PATCH v2 03/12] iio: accel: adxl313: configure scan type for buffer

[Lothar Rubusch]

According to the datasheet the ADXL313 uses 13 bit in full resolution.
Also, add signedness, storage bits and endianness.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313_core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 9c2f3af1d19f..06a771bb4726 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -184,7 +184,10 @@ static const int adxl313_odr_freqs[][2] = {
 	.info_mask_shared_by_type_available =				\
 		BIT(IIO_CHAN_INFO_SAMP_FREQ),				\
 	.scan_type = {							\
+		.sign = 's',						\
 		.realbits = 13,						\
+		.storagebits = 16,					\
+		.endianness = IIO_BE,					\
 	},								\
 }
 
-- 
2.39.5

[PATCH v2 04/12] iio: accel: adxl313: make use of regmap cache

[Lothar Rubusch]

Setup regmap cache to cache register configuration. This is a preparatory
step for follow up patches, to allow easy acces to the cached
configuration.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  2 ++
 drivers/iio/accel/adxl313_core.c | 17 +++++++++++++++++
 drivers/iio/accel/adxl313_i2c.c  |  6 ++++++
 drivers/iio/accel/adxl313_spi.c  |  6 ++++++
 4 files changed, 31 insertions(+)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index 72f624af4686..fc937bdf83b6 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -54,6 +54,8 @@ extern const struct regmap_access_table adxl312_writable_regs_table;
 extern const struct regmap_access_table adxl313_writable_regs_table;
 extern const struct regmap_access_table adxl314_writable_regs_table;
 
+bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg);
+
 enum adxl313_device_type {
 	ADXL312,
 	ADXL313,
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 06a771bb4726..0c893c286017 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -46,6 +46,23 @@ const struct regmap_access_table adxl314_readable_regs_table = {
 };
 EXPORT_SYMBOL_NS_GPL(adxl314_readable_regs_table, IIO_ADXL313);
 
+bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ADXL313_REG_DATA_AXIS(0):
+	case ADXL313_REG_DATA_AXIS(1):
+	case ADXL313_REG_DATA_AXIS(2):
+	case ADXL313_REG_DATA_AXIS(3):
+	case ADXL313_REG_DATA_AXIS(4):
+	case ADXL313_REG_DATA_AXIS(5):
+	case ADXL313_REG_FIFO_STATUS:
+		return true;
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_NS_GPL(adxl313_is_volatile_reg, "IIO_ADXL313");
+
 static int adxl312_check_id(struct device *dev,
 			    struct adxl313_data *data)
 {
diff --git a/drivers/iio/accel/adxl313_i2c.c b/drivers/iio/accel/adxl313_i2c.c
index a4cf0cf2c5aa..e8636e8ab14f 100644
--- a/drivers/iio/accel/adxl313_i2c.c
+++ b/drivers/iio/accel/adxl313_i2c.c
@@ -21,6 +21,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
 		.rd_table	= &adxl312_readable_regs_table,
 		.wr_table	= &adxl312_writable_regs_table,
 		.max_register	= 0x39,
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 	[ADXL313] = {
 		.reg_bits	= 8,
@@ -28,6 +30,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
 		.rd_table	= &adxl313_readable_regs_table,
 		.wr_table	= &adxl313_writable_regs_table,
 		.max_register	= 0x39,
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 	[ADXL314] = {
 		.reg_bits	= 8,
@@ -35,6 +39,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
 		.rd_table	= &adxl314_readable_regs_table,
 		.wr_table	= &adxl314_writable_regs_table,
 		.max_register	= 0x39,
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 };
 
diff --git a/drivers/iio/accel/adxl313_spi.c b/drivers/iio/accel/adxl313_spi.c
index 9a16b40bff34..68e323e81aeb 100644
--- a/drivers/iio/accel/adxl313_spi.c
+++ b/drivers/iio/accel/adxl313_spi.c
@@ -24,6 +24,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
 		.max_register	= 0x39,
 		/* Setting bits 7 and 6 enables multiple-byte read */
 		.read_flag_mask	= BIT(7) | BIT(6),
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 	[ADXL313] = {
 		.reg_bits	= 8,
@@ -33,6 +35,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
 		.max_register	= 0x39,
 		/* Setting bits 7 and 6 enables multiple-byte read */
 		.read_flag_mask	= BIT(7) | BIT(6),
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 	[ADXL314] = {
 		.reg_bits	= 8,
@@ -42,6 +46,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
 		.max_register	= 0x39,
 		/* Setting bits 7 and 6 enables multiple-byte read */
 		.read_flag_mask	= BIT(7) | BIT(6),
+		.volatile_reg	= adxl313_is_volatile_reg,
+		.cache_type	= REGCACHE_MAPLE,
 	},
 };
 
-- 
2.39.5

[PATCH v2 05/12] iio: accel: adxl313: add function to enable measurement

[Lothar Rubusch]

Add a function to enable measurement. The data-sheet recomments turning of
measurement while modifying certain config registers. This is a preparatory
step.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  3 ++-
 drivers/iio/accel/adxl313_core.c | 12 +++++++++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index fc937bdf83b6..ba5b5d53a0ea 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -36,8 +36,9 @@
 #define ADXL313_RATE_MSK		GENMASK(3, 0)
 #define ADXL313_RATE_BASE		6
 
-#define ADXL313_POWER_CTL_MSK		GENMASK(3, 2)
+#define ADXL313_POWER_CTL_MSK		BIT(3)
 #define ADXL313_MEASUREMENT_MODE	BIT(3)
+#define ADXL313_MEASUREMENT_STANDBY	0x00
 
 #define ADXL313_RANGE_MSK		GENMASK(1, 0)
 #define ADXL313_RANGE_MAX		3
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 0c893c286017..6c9d99650fc2 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -63,6 +63,14 @@ bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg)
 }
 EXPORT_SYMBOL_NS_GPL(adxl313_is_volatile_reg, "IIO_ADXL313");
 
+static int adxl313_set_measure_en(struct adxl313_data *data, bool en)
+{
+	unsigned int val = en ? ADXL313_MEASUREMENT_MODE : ADXL313_MEASUREMENT_STANDBY;
+
+	return regmap_update_bits(data->regmap, ADXL313_REG_POWER_CTL,
+				  ADXL313_POWER_CTL_MSK, val);
+}
+
 static int adxl312_check_id(struct device *dev,
 			    struct adxl313_data *data)
 {
@@ -410,9 +418,7 @@ static int adxl313_setup(struct device *dev, struct adxl313_data *data,
 	}
 
 	/* Enables measurement mode */
-	return regmap_update_bits(data->regmap, ADXL313_REG_POWER_CTL,
-				  ADXL313_POWER_CTL_MSK,
-				  ADXL313_MEASUREMENT_MODE);
+	return adxl313_set_measure_en(data, true);
 }
 
 /**
-- 
2.39.5

[PATCH v2 06/12] iio: accel: adxl313: prepare interrupt handling

[Lothar Rubusch]

Evaluate the devicetree property for an optional interrupt line, and
configure the interrupt mapping accordingly. When no interrupt line
is defined in the devicetree, keep the FIFO in bypass mode as before.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  8 ++++++++
 drivers/iio/accel/adxl313_core.c | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index ba5b5d53a0ea..c5673f1934fb 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -21,7 +21,9 @@
 #define ADXL313_REG_ACT_INACT_CTL	0x27
 #define ADXL313_REG_BW_RATE		0x2C
 #define ADXL313_REG_POWER_CTL		0x2D
+#define ADXL313_REG_INT_ENABLE		0x2E
 #define ADXL313_REG_INT_MAP		0x2F
+#define ADXL313_REG_INT_SOURCE		0x30
 #define ADXL313_REG_DATA_FORMAT		0x31
 #define ADXL313_REG_DATA_AXIS(index)	(0x32 + ((index) * 2))
 #define ADXL313_REG_FIFO_CTL		0x38
@@ -47,6 +49,11 @@
 #define ADXL313_SPI_3WIRE		BIT(6)
 #define ADXL313_I2C_DISABLE		BIT(6)
 
+#define ADXL313_REG_FIFO_CTL_MODE_MSK		GENMASK(7, 6)
+
+#define ADXL313_FIFO_BYPASS			0
+#define ADXL313_FIFO_STREAM			2
+
 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;
@@ -67,6 +74,7 @@ struct adxl313_data {
 	struct regmap	*regmap;
 	const struct adxl313_chip_info *chip_info;
 	struct mutex	lock; /* lock to protect transf_buf */
+	int irq;
 	__le16		transf_buf __aligned(IIO_DMA_MINALIGN);
 };
 
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 6c9d99650fc2..52fb10680939 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -8,11 +8,17 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/property.h>
 #include <linux/regmap.h>
 
 #include "adxl313.h"
 
+#define ADXL313_INT_NONE			U8_MAX
+#define ADXL313_INT1				1
+#define ADXL313_INT2				2
+
 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)),
@@ -438,6 +444,8 @@ int adxl313_core_probe(struct device *dev,
 {
 	struct adxl313_data *data;
 	struct iio_dev *indio_dev;
+	unsigned int regval;
+	u8 int_line;
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
@@ -463,6 +471,30 @@ int adxl313_core_probe(struct device *dev,
 		return ret;
 	}
 
+	int_line = ADXL313_INT1;
+	data->irq = fwnode_irq_get_byname(dev_fwnode(dev), "INT1");
+	if (data->irq < 0) {
+		int_line = ADXL313_INT2;
+		data->irq = fwnode_irq_get_byname(dev_fwnode(dev), "INT2");
+		if (data->irq < 0)
+			int_line = ADXL313_INT_NONE;
+	}
+
+	if (int_line == ADXL313_INT1 || int_line == ADXL313_INT2) {
+		/* FIFO_STREAM mode */
+		regval = int_line == ADXL313_INT2 ? 0xff : 0;
+		ret = regmap_write(data->regmap, ADXL313_REG_INT_MAP, regval);
+		if (ret)
+			return ret;
+	} else {
+		/* FIFO_BYPASSED mode */
+		ret = regmap_write(data->regmap, ADXL313_REG_FIFO_CTL,
+				   FIELD_PREP(ADXL313_REG_FIFO_CTL_MODE_MSK,
+					      ADXL313_FIFO_BYPASS));
+		if (ret)
+			return ret;
+	}
+
 	return devm_iio_device_register(dev, indio_dev);
 }
 EXPORT_SYMBOL_NS_GPL(adxl313_core_probe, IIO_ADXL313);
-- 
2.39.5

[PATCH v2 07/12] iio: accel: adxl313: add basic interrupt handling

[Lothar Rubusch]

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

Re: [PATCH v2 07/12] iio: accel: adxl313: add basic interrupt handling

[Andy Shevchenko]

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

[PATCH v2 08/12] iio: accel: adxl313: add FIFO watermark

[Lothar Rubusch]

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@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  1 +
 drivers/iio/accel/adxl313_core.c | 59 ++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index 4cb1fe1f2616..9c7aedf7da7a 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -89,6 +89,7 @@ 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 8eecd2851512..da89e13a100d 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -374,6 +374,25 @@ 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, watermark_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,
+				  watermark_mask, ADXL313_INT_WATERMARK);
+}
+
 static int adxl313_get_samples(struct adxl313_data *data)
 {
 	unsigned int regval = 0;
@@ -400,6 +419,7 @@ 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);
@@ -465,6 +485,41 @@ 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);
+	int i, ret;
+
+	if (samples <= 0)
+		return -EINVAL;
+
+	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;
+	int ret = -ENOENT;
+
+	if (FIELD_GET(ADXL313_INT_WATERMARK, int_stat)) {
+		samples = adxl313_get_samples(data);
+		if (samples < 0)
+			return -EINVAL;
+
+		ret = adxl313_fifo_push(indio_dev, samples);
+	}
+
+	return ret;
+}
+
 static irqreturn_t adxl313_irq_handler(int irq, void *p)
 {
 	struct iio_dev *indio_dev = p;
@@ -474,6 +529,9 @@ 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;
 
@@ -498,6 +556,7 @@ 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

Re: [PATCH v2 08/12] iio: accel: adxl313: add FIFO watermark

[Andy Shevchenko]

On Tue, May 20, 2025 at 10:50:03PM +0000, Lothar Rubusch wrote:
> 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.

...

> +	const unsigned int fifo_mask = 0x1f, watermark_mask  = 0x02;

Seems you have some (wrong) setting in the text editor?
One space too many again...

...

> +static int adxl313_fifo_push(struct iio_dev *indio_dev, int samples)
> +{
> +	struct adxl313_data *data = iio_priv(indio_dev);
> +	int i, ret;

Why is 'i' signed?

> +	if (samples <= 0)

What is the semantics of the negative samples? Is it an error code? Why not?
I believe it's ignored again from my previous review.

> +		return -EINVAL;
> +
> +	ret = adxl313_fifo_transfer(data, samples);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i  < ADXL313_NUM_AXIS * samples; i += ADXL313_NUM_AXIS)

Ouch, one space too many, *again*!

> +		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;
> +	int ret = -ENOENT;
> +
> +	if (FIELD_GET(ADXL313_INT_WATERMARK, int_stat)) {
> +		samples = adxl313_get_samples(data);
> +		if (samples < 0)
> +			return -EINVAL;
> +
> +		ret = adxl313_fifo_push(indio_dev, samples);
> +	}
> +
> +	return ret;
> +}

...and again... If you are going to ignore most of the comments, do not expect
your patches to be applied. I'm stopping here.

...

Also note, try to avoid sending a new version until the review is settled down
on a previous round.

...

With this being said, I stopped here. Take your time (you have now a few weeks)
and carefully address / discuss all mentioned pieces of the code in both review
rounds.

-- 
With Best Regards,
Andy Shevchenko

[PATCH v2 09/12] iio: accel: adxl313: add activity sensing

[Lothar Rubusch]

Add possibilities to set a threshold for activity sensing. Extend the
interrupt handler to process activity interrupts. Provide functions to set
the activity threshold and to enable/disable activity sensing. Further add
a fake channel for having x, y and z axis anded on the iio channel.

This is a preparatory patch. Some of the definitions and functions are
supposed to be extended for inactivity later on.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313_core.c | 230 +++++++++++++++++++++++++++++++
 1 file changed, 230 insertions(+)

diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index da89e13a100d..2ad87e98525c 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/property.h>
 #include <linux/regmap.h>
+#include <linux/units.h>
 
 #include <linux/iio/buffer.h>
 #include <linux/iio/events.h>
@@ -27,6 +28,21 @@
 
 #define ADXL313_REG_XYZ_BASE			ADXL313_REG_DATA_AXIS(0)
 
+#define ADXL313_ACT_XYZ_EN			GENMASK(6, 4)
+
+/* activity/inactivity */
+enum adxl313_activity_type {
+	ADXL313_ACTIVITY,
+};
+
+static const unsigned int adxl313_act_int_reg[] = {
+	[ADXL313_ACTIVITY] = ADXL313_INT_ACTIVITY,
+};
+
+static const unsigned int adxl313_act_thresh_reg[] = {
+	[ADXL313_ACTIVITY] = ADXL313_REG_THRESH_ACT,
+};
+
 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)),
@@ -231,6 +247,16 @@ static const int adxl313_odr_freqs[][2] = {
 	},								\
 }
 
+static const struct iio_event_spec adxl313_fake_chan_events[] = {
+	{
+		/* activity */
+		.type = IIO_EV_TYPE_MAG,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE),
+	},
+};
+
 enum adxl313_chans {
 	chan_x, chan_y, chan_z,
 };
@@ -239,6 +265,14 @@ static const struct iio_chan_spec adxl313_channels[] = {
 	ADXL313_ACCEL_CHANNEL(0, chan_x, X),
 	ADXL313_ACCEL_CHANNEL(1, chan_y, Y),
 	ADXL313_ACCEL_CHANNEL(2, chan_z, Z),
+	{
+		.type = IIO_ACCEL,
+		.modified = 1,
+		.channel2 = IIO_MOD_X_AND_Y_AND_Z,
+		.scan_index = -1, /* Fake channel for axis AND'ing */
+		.event_spec = adxl313_fake_chan_events,
+		.num_event_specs = ARRAY_SIZE(adxl313_fake_chan_events),
+	},
 };
 
 static const unsigned long adxl313_scan_masks[] = {
@@ -301,6 +335,66 @@ static int adxl313_read_freq_avail(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_is_act_inact_en(struct adxl313_data *data,
+				   enum adxl313_activity_type type)
+{
+	unsigned int axis_ctrl;
+	unsigned int regval;
+	int axis_en, int_en, ret;
+
+	ret = regmap_read(data->regmap, ADXL313_REG_ACT_INACT_CTL, &axis_ctrl);
+	if (ret)
+		return ret;
+
+	/* Check if axis for activity are enabled */
+	if (type == ADXL313_ACTIVITY)
+		axis_en = FIELD_GET(ADXL313_ACT_XYZ_EN, axis_ctrl);
+	else
+		return 0;
+
+	/* The axis are enabled, now check if specific interrupt is enabled */
+	ret = regmap_read(data->regmap, ADXL313_REG_INT_ENABLE, &regval);
+	if (ret)
+		return ret;
+
+	int_en = adxl313_act_int_reg[type] & regval;
+
+	return axis_en && int_en;
+}
+
+static int adxl313_set_act_inact_en(struct adxl313_data *data,
+				    enum adxl313_activity_type type,
+				    bool cmd_en)
+{
+	unsigned int axis_ctrl = 0;
+	unsigned int threshold;
+	bool en;
+	int ret;
+
+	if (type == ADXL313_ACTIVITY)
+		axis_ctrl = ADXL313_ACT_XYZ_EN;
+
+	ret = regmap_update_bits(data->regmap,
+				 ADXL313_REG_ACT_INACT_CTL,
+				 axis_ctrl,
+				 cmd_en ? 0xff : 0x00);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(data->regmap, adxl313_act_thresh_reg[type], &threshold);
+	if (ret)
+		return ret;
+
+	if (type == ADXL313_ACTIVITY)
+		en = cmd_en && threshold;
+	else
+		en = false;
+
+	return regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
+				  adxl313_act_int_reg[type],
+				  en ? adxl313_act_int_reg[type] : 0);
+}
+
 static int adxl313_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
@@ -374,6 +468,113 @@ static int adxl313_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_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 adxl313_data *data = iio_priv(indio_dev);
+
+	if (type != IIO_EV_TYPE_MAG)
+		return -EINVAL;
+
+	switch (dir) {
+	case IIO_EV_DIR_RISING:
+		return adxl313_is_act_inact_en(data, ADXL313_ACTIVITY);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int adxl313_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 adxl313_data *data = iio_priv(indio_dev);
+
+	if (type != IIO_EV_TYPE_MAG)
+		return -EINVAL;
+
+	switch (dir) {
+	case IIO_EV_DIR_RISING:
+		return adxl313_set_act_inact_en(data, ADXL313_ACTIVITY, state);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int adxl313_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 adxl313_data *data = iio_priv(indio_dev);
+	unsigned int act_threshold;
+	int ret;
+
+	/* Measurement stays enabled, reading from regmap cache */
+
+	if (type != IIO_EV_TYPE_MAG)
+		return -EINVAL;
+
+	if (info != IIO_EV_INFO_VALUE)
+		return -EINVAL;
+
+	switch (dir) {
+	case IIO_EV_DIR_RISING:
+		ret = regmap_read(data->regmap,
+				  adxl313_act_thresh_reg[ADXL313_ACTIVITY],
+				  &act_threshold);
+		if (ret)
+			return ret;
+		*val = act_threshold * 15625;
+		*val2 = MICRO;
+		return IIO_VAL_FRACTIONAL;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int adxl313_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)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	unsigned int regval;
+	int ret;
+
+	ret = adxl313_set_measure_en(data, false);
+	if (ret)
+		return ret;
+
+	if (type != IIO_EV_TYPE_MAG)
+		return -EINVAL;
+
+	if (info != IIO_EV_INFO_VALUE)
+		return -EINVAL;
+
+	/* Scale factor 15.625 mg/LSB */
+	regval = DIV_ROUND_CLOSEST(MICRO * val + val2, 15625);
+	switch (dir) {
+	case IIO_EV_DIR_RISING:
+		ret = regmap_write(data->regmap,
+				   adxl313_act_thresh_reg[ADXL313_ACTIVITY],
+				   regval);
+		if (ret)
+			return ret;
+		return adxl313_set_measure_en(data, true);
+	default:
+		return -EINVAL;
+	}
+}
+
 static int adxl313_set_watermark(struct iio_dev *indio_dev, unsigned int value)
 {
 	struct adxl313_data *data = iio_priv(indio_dev);
@@ -505,10 +706,22 @@ static int adxl313_fifo_push(struct iio_dev *indio_dev, int samples)
 
 static int adxl313_push_event(struct iio_dev *indio_dev, int int_stat)
 {
+	s64 ts = iio_get_time_ns(indio_dev);
 	struct adxl313_data *data =  iio_priv(indio_dev);
 	int samples;
 	int ret = -ENOENT;
 
+	if (FIELD_GET(ADXL313_INT_ACTIVITY, int_stat)) {
+		ret = iio_push_event(indio_dev,
+				     IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
+							IIO_MOD_X_AND_Y_AND_Z,
+							IIO_EV_TYPE_MAG,
+							IIO_EV_DIR_RISING),
+				     ts);
+		if (ret)
+			return ret;
+	}
+
 	if (FIELD_GET(ADXL313_INT_WATERMARK, int_stat)) {
 		samples = adxl313_get_samples(data);
 		if (samples < 0)
@@ -555,6 +768,10 @@ static int adxl313_reg_access(struct iio_dev *indio_dev, unsigned int reg,
 static const struct iio_info adxl313_info = {
 	.read_raw	= adxl313_read_raw,
 	.write_raw	= adxl313_write_raw,
+	.read_event_config = adxl313_read_event_config,
+	.write_event_config = adxl313_write_event_config,
+	.read_event_value = adxl313_read_event_value,
+	.write_event_value = adxl313_write_event_value,
 	.read_avail	= adxl313_read_freq_avail,
 	.hwfifo_set_watermark = adxl313_set_watermark,
 	.debugfs_reg_access = &adxl313_reg_access,
@@ -665,6 +882,19 @@ int adxl313_core_probe(struct device *dev,
 		if (ret)
 			return ret;
 
+		/*
+		 * Reset or configure the registers with reasonable default
+		 * values. As having 0 in most cases may result in undesirable
+		 * behavior if the interrupts are enabled.
+		 */
+		ret = regmap_write(data->regmap, ADXL313_REG_ACT_INACT_CTL, 0x00);
+		if (ret)
+			return ret;
+
+		ret = regmap_write(data->regmap, ADXL313_REG_THRESH_ACT, 0x52);
+		if (ret)
+			return ret;
+
 		ret  = devm_iio_kfifo_buffer_setup(dev, indio_dev,
 						   &adxl313_buffer_ops);
 		if (ret)
-- 
2.39.5

Re: [PATCH v2 09/12] iio: accel: adxl313: add activity sensing

[Andy Shevchenko]

On Tue, May 20, 2025 at 10:50:04PM +0000, Lothar Rubusch wrote:
> Add possibilities to set a threshold for activity sensing. Extend the
> interrupt handler to process activity interrupts. Provide functions to set
> the activity threshold and to enable/disable activity sensing. Further add
> a fake channel for having x, y and z axis anded on the iio channel.
> 
> This is a preparatory patch. Some of the definitions and functions are
> supposed to be extended for inactivity later on.

...

> +	int axis_en, int_en, ret;
> +
> +	ret = regmap_read(data->regmap, ADXL313_REG_ACT_INACT_CTL, &axis_ctrl);
> +	if (ret)
> +		return ret;

> +	/* Check if axis for activity are enabled */
> +	if (type == ADXL313_ACTIVITY)
> +		axis_en = FIELD_GET(ADXL313_ACT_XYZ_EN, axis_ctrl);
> +	else

Probably redundant 'else'. Wouldn't

	if (!=)
		return 0;

work?

> +		return 0;

> +	/* The axis are enabled, now check if specific interrupt is enabled */
> +	ret = regmap_read(data->regmap, ADXL313_REG_INT_ENABLE, &regval);
> +	if (ret)
> +		return ret;

> +	int_en = adxl313_act_int_reg[type] & regval;
> +
> +	return axis_en && int_en;

With the above these lines become:

	if (FIELD_GET(ADXL313_ACT_XYZ_EN, axis_ctrl) == 0)
		return 0;

	return !!(adxl313_act_int_reg[type] & regval);

...

> +	ret = regmap_update_bits(data->regmap,
> +				 ADXL313_REG_ACT_INACT_CTL,
> +				 axis_ctrl,
> +				 cmd_en ? 0xff : 0x00);

Please, utilize given space. You have a lot of it in each line above.

> +	if (ret)
> +		return ret;

-- 
With Best Regards,
Andy Shevchenko

[PATCH v2 10/12] iio: accel: adxl313: add inactivity sensing

[Lothar Rubusch]

Extend the interrupt handler to process interrupts as inactivity events.
Add functions to set threshold and period registers for inactivity. Add
functions to enable / disable inactivity. Extend the fake iio channel to
deal with inactivity events on x, y and z combined with AND.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |   2 +
 drivers/iio/accel/adxl313_core.c | 138 +++++++++++++++++++++++++------
 2 files changed, 114 insertions(+), 26 deletions(-)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index 9c7aedf7da7a..1398ac54d19b 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -18,6 +18,8 @@
 #define ADXL313_REG_SOFT_RESET		0x18
 #define ADXL313_REG_OFS_AXIS(index)	(0x1E + (index))
 #define ADXL313_REG_THRESH_ACT		0x24
+#define ADXL313_REG_THRESH_INACT	0x25
+#define ADXL313_REG_TIME_INACT		0x26
 #define ADXL313_REG_ACT_INACT_CTL	0x27
 #define ADXL313_REG_BW_RATE		0x2C
 #define ADXL313_REG_POWER_CTL		0x2D
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 2ad87e98525c..7356aacd8874 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -29,18 +29,22 @@
 #define ADXL313_REG_XYZ_BASE			ADXL313_REG_DATA_AXIS(0)
 
 #define ADXL313_ACT_XYZ_EN			GENMASK(6, 4)
+#define ADXL313_INACT_XYZ_EN			GENMASK(2, 0)
 
 /* activity/inactivity */
 enum adxl313_activity_type {
 	ADXL313_ACTIVITY,
+	ADXL313_INACTIVITY,
 };
 
 static const unsigned int adxl313_act_int_reg[] = {
 	[ADXL313_ACTIVITY] = ADXL313_INT_ACTIVITY,
+	[ADXL313_INACTIVITY] = ADXL313_INT_INACTIVITY,
 };
 
 static const unsigned int adxl313_act_thresh_reg[] = {
 	[ADXL313_ACTIVITY] = ADXL313_REG_THRESH_ACT,
+	[ADXL313_INACTIVITY] = ADXL313_REG_THRESH_INACT,
 };
 
 static const struct regmap_range adxl312_readable_reg_range[] = {
@@ -255,6 +259,14 @@ static const struct iio_event_spec adxl313_fake_chan_events[] = {
 		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
 		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE),
 	},
+	{
+		/* inactivity */
+		.type = IIO_EV_TYPE_MAG,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
+			BIT(IIO_EV_INFO_PERIOD),
+	},
 };
 
 enum adxl313_chans {
@@ -335,6 +347,15 @@ static int adxl313_read_freq_avail(struct iio_dev *indio_dev,
 	}
 }
 
+static int adxl313_set_inact_time_s(struct adxl313_data *data,
+				    unsigned int val_s)
+{
+	unsigned int max_boundary = 255;
+	unsigned int val = min(val_s, max_boundary);
+
+	return regmap_write(data->regmap, ADXL313_REG_TIME_INACT, val);
+}
+
 static int adxl313_is_act_inact_en(struct adxl313_data *data,
 				   enum adxl313_activity_type type)
 {
@@ -350,7 +371,7 @@ static int adxl313_is_act_inact_en(struct adxl313_data *data,
 	if (type == ADXL313_ACTIVITY)
 		axis_en = FIELD_GET(ADXL313_ACT_XYZ_EN, axis_ctrl);
 	else
-		return 0;
+		axis_en = FIELD_GET(ADXL313_INACT_XYZ_EN, axis_ctrl);
 
 	/* The axis are enabled, now check if specific interrupt is enabled */
 	ret = regmap_read(data->regmap, ADXL313_REG_INT_ENABLE, &regval);
@@ -366,13 +387,16 @@ static int adxl313_set_act_inact_en(struct adxl313_data *data,
 				    enum adxl313_activity_type type,
 				    bool cmd_en)
 {
-	unsigned int axis_ctrl = 0;
+	unsigned int axis_ctrl;
 	unsigned int threshold;
+	unsigned int inact_time_s;
 	bool en;
 	int ret;
 
 	if (type == ADXL313_ACTIVITY)
 		axis_ctrl = ADXL313_ACT_XYZ_EN;
+	else
+		axis_ctrl = ADXL313_INACT_XYZ_EN;
 
 	ret = regmap_update_bits(data->regmap,
 				 ADXL313_REG_ACT_INACT_CTL,
@@ -385,10 +409,14 @@ static int adxl313_set_act_inact_en(struct adxl313_data *data,
 	if (ret)
 		return ret;
 
-	if (type == ADXL313_ACTIVITY)
-		en = cmd_en && threshold;
-	else
-		en = false;
+	en = cmd_en && threshold;
+	if (type == ADXL313_INACTIVITY) {
+		ret = regmap_read(data->regmap, ADXL313_REG_TIME_INACT, &inact_time_s);
+		if (ret)
+			return ret;
+
+		en = en && inact_time_s;
+	}
 
 	return regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
 				  adxl313_act_int_reg[type],
@@ -481,6 +509,8 @@ static int adxl313_read_event_config(struct iio_dev *indio_dev,
 	switch (dir) {
 	case IIO_EV_DIR_RISING:
 		return adxl313_is_act_inact_en(data, ADXL313_ACTIVITY);
+	case  IIO_EV_DIR_FALLING:
+		return adxl313_is_act_inact_en(data, ADXL313_INACTIVITY);
 	default:
 		return -EINVAL;
 	}
@@ -500,6 +530,8 @@ static int adxl313_write_event_config(struct iio_dev *indio_dev,
 	switch (dir) {
 	case IIO_EV_DIR_RISING:
 		return adxl313_set_act_inact_en(data, ADXL313_ACTIVITY, state);
+	case IIO_EV_DIR_FALLING:
+		return adxl313_set_act_inact_en(data, ADXL313_INACTIVITY, state);
 	default:
 		return -EINVAL;
 	}
@@ -514,6 +546,8 @@ static int adxl313_read_event_value(struct iio_dev *indio_dev,
 {
 	struct adxl313_data *data = iio_priv(indio_dev);
 	unsigned int act_threshold;
+	unsigned int inact_threshold;
+	unsigned int inact_time_s;
 	int ret;
 
 	/* Measurement stays enabled, reading from regmap cache */
@@ -521,19 +555,38 @@ static int adxl313_read_event_value(struct iio_dev *indio_dev,
 	if (type != IIO_EV_TYPE_MAG)
 		return -EINVAL;
 
-	if (info != IIO_EV_INFO_VALUE)
-		return -EINVAL;
-
-	switch (dir) {
-	case IIO_EV_DIR_RISING:
+	switch (info) {
+	case IIO_EV_INFO_VALUE:
+		switch (dir) {
+		case IIO_EV_DIR_RISING:
+			ret = regmap_read(data->regmap,
+					  adxl313_act_thresh_reg[ADXL313_ACTIVITY],
+					  &act_threshold);
+			if (ret)
+				return ret;
+			*val = act_threshold * 15625;
+			*val2 = MICRO;
+			return IIO_VAL_FRACTIONAL;
+		case IIO_EV_DIR_FALLING:
+			ret = regmap_read(data->regmap,
+					  adxl313_act_thresh_reg[ADXL313_INACTIVITY],
+					  &inact_threshold);
+			if (ret)
+				return ret;
+			*val = inact_threshold * 15625;
+			*val2 = MICRO;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
+	case IIO_EV_INFO_PERIOD:
 		ret = regmap_read(data->regmap,
-				  adxl313_act_thresh_reg[ADXL313_ACTIVITY],
-				  &act_threshold);
+				  ADXL313_REG_TIME_INACT,
+				  &inact_time_s);
 		if (ret)
 			return ret;
-		*val = act_threshold * 15625;
-		*val2 = MICRO;
-		return IIO_VAL_FRACTIONAL;
+		*val = inact_time_s;
+		return IIO_VAL_INT;
 	default:
 		return -EINVAL;
 	}
@@ -557,16 +610,30 @@ static int adxl313_write_event_value(struct iio_dev *indio_dev,
 	if (type != IIO_EV_TYPE_MAG)
 		return -EINVAL;
 
-	if (info != IIO_EV_INFO_VALUE)
-		return -EINVAL;
-
-	/* Scale factor 15.625 mg/LSB */
-	regval = DIV_ROUND_CLOSEST(MICRO * val + val2, 15625);
-	switch (dir) {
-	case IIO_EV_DIR_RISING:
-		ret = regmap_write(data->regmap,
-				   adxl313_act_thresh_reg[ADXL313_ACTIVITY],
-				   regval);
+	switch (info) {
+	case IIO_EV_INFO_VALUE:
+		/* The scale factor is 15.625 mg/LSB */
+		regval = DIV_ROUND_CLOSEST(MICRO * val + val2, 15625);
+		switch (dir) {
+		case IIO_EV_DIR_RISING:
+			ret = regmap_write(data->regmap,
+					   adxl313_act_thresh_reg[ADXL313_ACTIVITY],
+					   regval);
+			if (ret)
+				return ret;
+			return adxl313_set_measure_en(data, true);
+		case IIO_EV_DIR_FALLING:
+			ret = regmap_write(data->regmap,
+					   adxl313_act_thresh_reg[ADXL313_INACTIVITY],
+					   regval);
+			if (ret)
+				return ret;
+			return adxl313_set_measure_en(data, true);
+		default:
+			return -EINVAL;
+		}
+	case IIO_EV_INFO_PERIOD:
+		ret = adxl313_set_inact_time_s(data, val);
 		if (ret)
 			return ret;
 		return adxl313_set_measure_en(data, true);
@@ -722,6 +789,17 @@ static int adxl313_push_event(struct iio_dev *indio_dev, int int_stat)
 			return ret;
 	}
 
+	if (FIELD_GET(ADXL313_INT_INACTIVITY, int_stat)) {
+		ret = iio_push_event(indio_dev,
+				     IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
+							IIO_MOD_X_AND_Y_AND_Z,
+							IIO_EV_TYPE_MAG,
+							IIO_EV_DIR_FALLING),
+				     ts);
+		if (ret)
+			return ret;
+	}
+
 	if (FIELD_GET(ADXL313_INT_WATERMARK, int_stat)) {
 		samples = adxl313_get_samples(data);
 		if (samples < 0)
@@ -891,6 +969,14 @@ int adxl313_core_probe(struct device *dev,
 		if (ret)
 			return ret;
 
+		ret = regmap_write(data->regmap, ADXL313_REG_TIME_INACT, 5);
+		if (ret)
+			return ret;
+
+		ret = regmap_write(data->regmap, ADXL313_REG_THRESH_INACT, 0x4f);
+		if (ret)
+			return ret;
+
 		ret = regmap_write(data->regmap, ADXL313_REG_THRESH_ACT, 0x52);
 		if (ret)
 			return ret;
-- 
2.39.5

[PATCH v2 11/12] iio: accel: adxl313: implement power-save on inactivity

[Lothar Rubusch]

Link activity and inactivity to indicate the internal power-saving state.
Add auto-sleep to be linked to inactivity.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 drivers/iio/accel/adxl313.h      |  3 +++
 drivers/iio/accel/adxl313_core.c | 29 ++++++++++++++++++++++++++---
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
index 1398ac54d19b..eafdf8f57816 100644
--- a/drivers/iio/accel/adxl313.h
+++ b/drivers/iio/accel/adxl313.h
@@ -41,6 +41,9 @@
 #define ADXL313_RATE_BASE		6
 
 #define ADXL313_POWER_CTL_MSK		BIT(3)
+#define ADXL313_POWER_CTL_INACT_MSK	GENMASK(5, 4)
+#define ADXL313_POWER_CTL_LINK		BIT(5)
+#define ADXL313_POWER_CTL_AUTO_SLEEP	BIT(4)
 #define ADXL313_MEASUREMENT_MODE	BIT(3)
 #define ADXL313_MEASUREMENT_STANDBY	0x00
 
diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
index 7356aacd8874..2b24e6b01f1f 100644
--- a/drivers/iio/accel/adxl313_core.c
+++ b/drivers/iio/accel/adxl313_core.c
@@ -390,6 +390,7 @@ static int adxl313_set_act_inact_en(struct adxl313_data *data,
 	unsigned int axis_ctrl;
 	unsigned int threshold;
 	unsigned int inact_time_s;
+	int act_en, inact_en;
 	bool en;
 	int ret;
 
@@ -418,9 +419,31 @@ static int adxl313_set_act_inact_en(struct adxl313_data *data,
 		en = en && inact_time_s;
 	}
 
-	return regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
-				  adxl313_act_int_reg[type],
-				  en ? adxl313_act_int_reg[type] : 0);
+	ret = regmap_update_bits(data->regmap, ADXL313_REG_INT_ENABLE,
+				 adxl313_act_int_reg[type],
+				 en ? adxl313_act_int_reg[type] : 0);
+	if (ret)
+		return ret;
+
+	/*
+	 * Advanced power saving: Set sleep and link bit only when ACT and INACT
+	 * are set. Check enable against regmap cached values.
+	 */
+	act_en = adxl313_is_act_inact_en(data, ADXL313_ACTIVITY);
+	if (act_en < 0)
+		return act_en;
+
+	inact_en = adxl313_is_act_inact_en(data, ADXL313_INACTIVITY);
+	if (inact_en < 0)
+		return inact_en;
+
+	en = en && act_en && inact_en;
+
+	return regmap_update_bits(data->regmap,
+				  ADXL313_REG_POWER_CTL,
+				  ADXL313_POWER_CTL_INACT_MSK,
+				  en ?
+				  (ADXL313_POWER_CTL_AUTO_SLEEP | ADXL313_POWER_CTL_LINK) : 0);
 }
 
 static int adxl313_read_raw(struct iio_dev *indio_dev,
-- 
2.39.5

[PATCH v2 12/12] docs: iio: add ADXL313 accelerometer

[Lothar Rubusch]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=y, Size: 9652 bytes --]

Add documentation for the ADXL313 accelerometer driver.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
 Documentation/iio/adxl313.rst | 196 ++++++++++++++++++++++++++++++++++
 Documentation/iio/index.rst   |   1 +
 2 files changed, 197 insertions(+)
 create mode 100644 Documentation/iio/adxl313.rst

diff --git a/Documentation/iio/adxl313.rst b/Documentation/iio/adxl313.rst
new file mode 100644
index 000000000000..8c4e2d141594
--- /dev/null
+++ b/Documentation/iio/adxl313.rst
@@ -0,0 +1,196 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+ADXL313 driver
+===============
+
+This driver supports Analog Device's ADXL313 on SPI/I2C bus.
+
+1. Supported devices
+====================
+
+* `ADXL313 <https://www.analog.com/ADXL313>`_
+
+The ADXL313is a low noise density, low power, 3-axis accelerometer with
+selectable measurement ranges. The ADXL313 supports the ±0.5 g, ±1 g, ±2 g and
+±4 g ranges.
+
+2. Device attributes
+====================
+
+Accelerometer measurements are always provided.
+
+Temperature data are also provided. This data can be used to monitor the
+internal system temperature or to improve the temperature stability of the
+device via calibration.
+
+Each IIO device, has a device folder under ``/sys/bus/iio/devices/iio:deviceX``,
+where X is the IIO index of the device. Under these folders reside a set of
+device files, depending on the characteristics and features of the hardware
+device in questions. These files are consistently generalized and documented in
+the IIO ABI documentation.
+
+The following tables show the adxl313 related device files, found in the
+specific device folder path ``/sys/bus/iio/devices/iio:deviceX``.
+
++---------------------------------------------------+----------------------------------------------------------+
+| 3-Axis Accelerometer related device files         | Description                                              |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_scale                                    | Scale for the accelerometer channels.                    |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_x_calibbias                              | Calibration offset for the X-axis accelerometer channel. |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_x_raw                                    | Raw X-axis accelerometer channel value.                  |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_y_calibbias                              | y-axis acceleration offset correction                    |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_y_raw                                    | Raw Y-axis accelerometer channel value.                  |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_z_calibbias                              | Calibration offset for the Z-axis accelerometer channel. |
++---------------------------------------------------+----------------------------------------------------------+
+| in_accel_z_raw                                    | Raw Z-axis accelerometer channel value.                  |
++---------------------------------------------------+----------------------------------------------------------+
+
++---------------------------------------+----------------------------------------------+
+| Miscellaneous device files            | Description                                  |
++---------------------------------------+----------------------------------------------+
+| name                                  | Name of the IIO device.                      |
++---------------------------------------+----------------------------------------------+
+| in_accel_sampling_frequency           | Currently selected sample rate.              |
++---------------------------------------+----------------------------------------------+
+| in_accel_sampling_frequency_available | Available sampling frequency configurations. |
++---------------------------------------+----------------------------------------------+
+
+Channels processed values
+-------------------------
+
+A channel value can be read from its _raw attribute. The value returned is the
+raw value as reported by the devices. To get the processed value of the channel,
+apply the following formula:
+
+.. code-block:: bash
+
+        processed value = (_raw + _offset) * _scale
+
+Where _offset and _scale are device attributes. If no _offset attribute is
+present, simply assume its value is 0.
+
+The ADXL313 driver offers data for a single types of channels, the table below
+shows the measurement units for the processed value, which are defined by the
+IIO framework:
+
++-------------------------------------+---------------------------+
+| Channel type                        | Measurement unit          |
++-------------------------------------+---------------------------+
+| Acceleration on X, Y, and Z axis    | Meters per Second squared |
++-------------------------------------+---------------------------+
+
+Usage examples
+--------------
+
+Show device name:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> cat name
+        adxl313
+
+Show accelerometer channels value:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_raw
+        2
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_y_raw
+        -57
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_z_raw
+        2
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_scale
+        0.009576806
+
+- X-axis acceleration = in_accel_x_raw * in_accel_scale = 0.0191536 m/s^2
+- Y-axis acceleration = in_accel_y_raw * in_accel_scale = -0.5458779 m/s^2
+- Z-axis acceleration = in_accel_z_raw * in_accel_scale = 0.0191536 m/s^2
+
+Set calibration offset for accelerometer channels. Note, the calibration will be
+rounded according to the graduation of LSB units:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
+        0
+
+        root:/sys/bus/iio/devices/iio:device0> echo 50 > in_accel_x_calibbias
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
+        48
+
+Set sampling frequency:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_sampling_frequency
+        100.000000
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_sampling_frequency_available
+        6.250000 12.500000 25.000000 50.000000 100.000000 200.000000 400.000000 800.000000 1600.000000 3200.000000
+
+        root:/sys/bus/iio/devices/iio:device0> echo 400 > in_accel_sampling_frequency
+        root:/sys/bus/iio/devices/iio:device0> cat in_accel_sampling_frequency
+        400.000000
+
+3. Device buffers
+=================
+
+This driver supports IIO buffers.
+
+All devices support retrieving the raw acceleration measurements using buffers.
+
+Usage examples
+--------------
+
+Select channels for buffer read:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_x_en
+        root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_y_en
+        root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_z_en
+
+Set the number of samples to be stored in the buffer:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> echo 10 > buffer/length
+
+Enable buffer readings:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> echo 1 > buffer/enable
+
+Obtain buffered data:
+
+.. code-block:: bash
+
+        root:/sys/bus/iio/devices/iio:device0> hexdump -C /dev/iio\:device0
+        ...
+        000000d0  01 fc 31 00 c7 ff 03 fc  31 00 c7 ff 04 fc 33 00  |..1.....1.....3.|
+        000000e0  c8 ff 03 fc 32 00 c5 ff  ff fc 32 00 c7 ff 0a fc  |....2.....2.....|
+        000000f0  30 00 c8 ff 06 fc 33 00  c7 ff 01 fc 2f 00 c8 ff  |0.....3...../...|
+        00000100  02 fc 32 00 c6 ff 04 fc  33 00 c8 ff 05 fc 33 00  |..2.....3.....3.|
+        00000110  ca ff 02 fc 31 00 c7 ff  02 fc 30 00 c9 ff 09 fc  |....1.....0.....|
+        00000120  35 00 c9 ff 08 fc 35 00  c8 ff 02 fc 31 00 c5 ff  |5.....5.....1...|
+        00000130  03 fc 32 00 c7 ff 04 fc  32 00 c7 ff 02 fc 31 00  |..2.....2.....1.|
+        00000140  c7 ff 08 fc 30 00 c7 ff  02 fc 32 00 c5 ff ff fc  |....0.....2.....|
+        00000150  31 00 c5 ff 04 fc 31 00  c8 ff 03 fc 32 00 c8 ff  |1.....1.....2...|
+        00000160  01 fc 31 00 c7 ff 05 fc  31 00 c3 ff 04 fc 31 00  |..1.....1.....1.|
+        00000170  c5 ff 04 fc 30 00 c7 ff  03 fc 31 00 c9 ff 03 fc  |....0.....1.....|
+        ...
+
+See ``Documentation/iio/iio_devbuf.rst`` for more information about how buffered
+data is structured.
+
+4. IIO Interfacing Tools
+========================
+
+See ``Documentation/iio/iio_tools.rst`` for the description of the available IIO
+interfacing tools.
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 2d6afc5a8ed5..c106402a91f7 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -31,6 +31,7 @@ Industrial I/O Kernel Drivers
    adis16475
    adis16480
    adis16550
+   adxl313
    adxl380
    bno055
    ep93xx_adc
-- 
2.39.5