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Message-Id: <20251020201653.86181-3-duttaditya18@gmail.com>
Date: Tue, 21 Oct 2025 01:46:53 +0530
From: Aditya Dutt <duttaditya18@...il.com>
To: Jonathan Cameron <jic23@...nel.org>,
David Lechner <dlechner@...libre.com>,
Nuno Sá <nuno.sa@...log.com>,
Andy Shevchenko <andy@...nel.org>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
Jonathan Corbet <corbet@....net>,
Frank Zago <frank@...o.net>
Cc: Aditya Dutt <duttaditya18@...il.com>,
linux-kernel@...r.kernel.org,
linux-iio@...r.kernel.org,
devicetree@...r.kernel.org,
linux-doc@...r.kernel.org
Subject: [PATCH 2/2] iio: position: Add support for ams AS5600 angle sensor
The AS5600 is a Hall-based rotary magnetic position sensor using
planar sensors that convert the magnetic field component perpendicular
to the surface of the chip into a voltage, or a numerical value
available through i2c.
The driver registers the chip as an IIO_ANGL device.
It also exposes the raw registers through debugfs for further configuration.
Datasheet: https://ams-osram.com/products/sensor-solutions/position-sensors/ams-as5600-position-sensor
Co-developed-by: Frank Zago <frank@...o.net>
Signed-off-by: Frank Zago <frank@...o.net>
Signed-off-by: Aditya Dutt <duttaditya18@...il.com>
---
Documentation/iio/as5600.rst | 84 ++++++++
Documentation/iio/index.rst | 1 +
MAINTAINERS | 8 +
drivers/iio/position/Kconfig | 10 +
drivers/iio/position/Makefile | 1 +
drivers/iio/position/as5600.c | 373 ++++++++++++++++++++++++++++++++++
6 files changed, 477 insertions(+)
create mode 100644 Documentation/iio/as5600.rst
create mode 100644 drivers/iio/position/as5600.c
diff --git a/Documentation/iio/as5600.rst b/Documentation/iio/as5600.rst
new file mode 100644
index 000000000000..d74c4052e590
--- /dev/null
+++ b/Documentation/iio/as5600.rst
@@ -0,0 +1,84 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+=================
+ams AS5600 driver
+=================
+
+
+Overview
+========
+
+The ams AS5600 is a 12-Bit Programmable Contactless Potentiometer. Its
+i2c address is 0x36.
+
+For more information, see the datasheet at
+
+ https://ams-osram.com/products/sensor-solutions/position-sensors/ams-as5600-position-sensor
+
+
+Channels
+========
+
+The driver provides **two channels**:
+
+- **Channel 0**: raw, unscaled angle measurement
+- **Channel 1**: scaled angle measurement according to the configured
+ ``ZPOS`` / ``MPOS`` range
+
+``ZPOS`` and ``MPOS`` let a user restrict the angle returned, which improves
+the precision returned, since the angle returned is still in the 0 to
+4095 range. The minimal angle recommended is 18 degrees.
+
+The following files are exposed under ``/sys/bus/iio/devices/iio:deviceX``
+where X is the IIO index of the device.
+
++----------------+-------------------------------------------------+
+| File | Description |
++================+=================================================+
+| in_angl0_raw | Raw angle measurement |
++----------------+-------------------------------------------------+
+| in_angl0_scale | Scale for channel 0 |
++----------------+-------------------------------------------------+
+| in_angl1_raw | Adjusted angle measurement, scaled by ZPOS/MPOS |
++----------------+-------------------------------------------------+
+| in_angl1_scale | Scale for channel 1 |
++----------------+-------------------------------------------------+
+
+
+Accessing the device registers
+==============================
+
+The driver exposes direct register access via debugfs. This allows reading and
+writing I2C registers for debugging or configuration.
+
+Assuming the device is iio:deviceX, its debugfs path will be:
+
+.. code-block:: sh
+
+ $ AS5600=/sys/kernel/debug/iio/iio:deviceX/direct_reg_access
+
+Locate the index of a register to access in the datasheet, then use
+the following commands to read a value:
+
+.. code-block:: sh
+
+ $ echo <reg> > $AS5600/direct_reg_access
+ $ cat $AS5600/direct_reg_access
+
+or this to write a value:
+
+.. code-block:: sh
+
+ $ echo <reg> <value> > $AS5600/direct_reg_access
+
+For instance, this would return the lower byte of RAW ANGLE.
+
+.. code-block:: sh
+
+ $ echo 0x0D > $AS5600/direct_reg_access
+ $ cat $AS5600/direct_reg_access
+
+.. warning::
+
+ Register ``BURN`` (0xFF) permanently modifies device behavior.
+ Use with caution after reading the datasheet carefully.
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 315ae37d6fd4..14d097f753f1 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -35,6 +35,7 @@ Industrial I/O Kernel Drivers
adxl313
adxl380
adxl345
+ as5600
bno055
ep93xx_adc
opt4060
diff --git a/MAINTAINERS b/MAINTAINERS
index 46126ce2f968..ffef001ea7c4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1368,6 +1368,14 @@ S: Maintained
F: Documentation/devicetree/bindings/media/amphion,vpu.yaml
F: drivers/media/platform/amphion/
+AMS AS5600 DRIVER
+M: Aditya Dutt <duttaditya18@...il.com>
+L: linux-iio@...r.kernel.org
+S: Maintained
+F: Documentation/devicetree/bindings/iio/position/ams,as5600.yaml
+F: Documentation/iio/as5600.rst
+F: drivers/iio/position/as5600.c
+
AMS AS73211 DRIVER
M: Christian Eggers <ceggers@...i.de>
L: linux-iio@...r.kernel.org
diff --git a/drivers/iio/position/Kconfig b/drivers/iio/position/Kconfig
index 1576a6380b53..111ed551ae79 100644
--- a/drivers/iio/position/Kconfig
+++ b/drivers/iio/position/Kconfig
@@ -6,6 +6,16 @@
menu "Linear and angular position sensors"
+config AS5600
+ tristate "ams AS5600 angular position sensor"
+ depends on I2C
+ help
+ Say Y here if you want to build support for the ams 5600
+ 12-Bit Programmable Contactless Potentiometer.
+
+ To compile this driver as a module, choose M here: the module
+ will be called as5600.
+
config IQS624_POS
tristate "Azoteq IQS624/625 angular position sensors"
depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/iio/position/Makefile b/drivers/iio/position/Makefile
index d70902f2979d..53930681e6a4 100644
--- a/drivers/iio/position/Makefile
+++ b/drivers/iio/position/Makefile
@@ -4,5 +4,6 @@
# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AS5600) += as5600.o
obj-$(CONFIG_HID_SENSOR_CUSTOM_INTEL_HINGE) += hid-sensor-custom-intel-hinge.o
obj-$(CONFIG_IQS624_POS) += iqs624-pos.o
diff --git a/drivers/iio/position/as5600.c b/drivers/iio/position/as5600.c
new file mode 100644
index 000000000000..fe716d521548
--- /dev/null
+++ b/drivers/iio/position/as5600.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ams AS5600 -- 12-Bit Programmable Contactless Potentiometer
+ *
+ * Copyright (c) 2021 Frank Zago
+ * Copyright (c) 2025 Aditya Dutt
+ *
+ * datasheet
+ * https://ams-osram.com/products/sensor-solutions/position-sensors/ams-as5600-position-sensor
+ *
+ * The rotating magnet is installed from 0.5mm to 3mm parallel to and
+ * above the chip.
+ *
+ * The raw angle value returned by the chip is [0..4095]. The channel
+ * 0 (in_angl0_raw) returns the unscaled and unmodified angle, always
+ * covering the 360 degrees. The channel 1 returns the chip adjusted
+ * angle, covering from 18 to 360 degrees, as modified by its
+ * ZPOS/MPOS/MANG values,
+ *
+ * ZPOS and MPOS can be programmed through their debugfs entries. The
+ * MANG register doesn't appear to be programmable without flashing
+ * the chip.
+ *
+ * If the DIR pin is grounded, angles will increase when the magnet is
+ * turned clockwise. If DIR is connected to Vcc, it will be the opposite.
+ *
+ * The i2c address of the device is 0x36.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+
+/* Register definitions */
+#define AS5600_REG_ZMCO 0x00
+#define AS5600_MASK_ZMCO GENMASK(1, 0)
+#define AS5600_REG_ZPOS_H 0x01
+#define AS5600_MASK_ZPOS_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_ZPOS_L 0x02
+#define AS5600_REG_MPOS_H 0x03
+#define AS5600_MASK_MPOS_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_MPOS_L 0x04
+#define AS5600_REG_MANG_H 0x05
+#define AS5600_MASK_MANG_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_MANG_L 0x06
+#define AS5600_REG_CONF_H 0x07
+#define AS5600_MASK_CONF_H GENMASK(5, 0)
+#define AS5600_MASK_SF GENMASK(1, 0)
+#define AS5600_MASK_FTH GENMASK(4, 2)
+#define AS5600_MASK_WD BIT(5)
+#define AS5600_REG_CONF_L 0x08
+#define AS5600_MASK_PM GENMASK(1, 0)
+#define AS5600_MASK_HYST GENMASK(3, 2)
+#define AS5600_MASK_OUTS GENMASK(5, 4)
+#define AS5600_MASK_PWMF GENMASK(7, 6)
+#define AS5600_REG_STATUS 0x0B
+#define AS5600_MASK_STATUS GENMASK(5, 3)
+#define AS5600_MASK_MH BIT(3)
+#define AS5600_MASK_ML BIT(4)
+#define AS5600_MASK_MD BIT(5)
+#define AS5600_REG_RAW_ANGLE_H 0x0C
+#define AS5600_MASK_RAW_ANGLE_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_RAW_ANGLE_L 0x0D
+#define AS5600_REG_ANGLE_H 0x0E
+#define AS5600_MASK_ANGLE_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_ANGLE_L 0x0F
+#define AS5600_REG_AGC 0x1A
+#define AS5600_REG_MAGN_H 0x1B
+#define AS5600_MASK_MAGN_H GENMASK(3, 0) /* bits 11:8 */
+#define AS5600_REG_MAGN_L 0x1C
+#define AS5600_REG_BURN 0xFF
+
+/* Combined 16-bit register addresses for clarity */
+#define AS5600_REG_ZPOS 0x01
+#define AS5600_REG_MPOS 0x03
+#define AS5600_REG_RAW_ANGLE 0x0C
+#define AS5600_REG_ANGLE 0x0E
+
+/* Field masks for the entire 2 byte */
+#define AS5600_FIELD_ZPOS GENMASK(11, 0)
+#define AS5600_FIELD_MPOS GENMASK(11, 0)
+#define AS5600_FIELD_RAW_ANGLE GENMASK(11, 0)
+#define AS5600_FIELD_ANGLE GENMASK(11, 0)
+
+struct as5600_priv {
+ struct i2c_client *client;
+ struct mutex lock;
+ u16 zpos;
+ u16 mpos;
+};
+
+static int as5600_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct as5600_priv *priv = iio_priv(indio_dev);
+ u16 bitmask;
+ s32 ret;
+ u16 reg;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ if (chan->channel == 0) {
+ reg = AS5600_REG_RAW_ANGLE;
+ bitmask = AS5600_FIELD_RAW_ANGLE;
+ } else {
+ reg = AS5600_REG_ANGLE;
+ bitmask = AS5600_FIELD_ANGLE;
+ }
+ ret = i2c_smbus_read_word_swapped(priv->client, reg);
+
+ if (ret < 0)
+ return ret;
+ *val = ret & bitmask;
+
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ /* Always 4096 steps, but angle range varies between
+ * 18 and 360 degrees.
+ */
+ if (chan->channel == 0) {
+ /* Whole angle range = 2*pi / 4096 */
+ *val = 2 * 3141592;
+ *val2 = 4096000000;
+ } else {
+ s32 range;
+
+ /* MPOS - ZPOS defines the active angle selection */
+ /* Partial angle = (range / 4096) * (2*pi / 4096) */
+ mutex_lock(&priv->lock);
+ range = priv->mpos - priv->zpos;
+ mutex_unlock(&priv->lock);
+ if (range <= 0)
+ range += 4096;
+
+ *val = range * 2 * 314159;
+ *val /= 4096;
+ *val2 = 409600000;
+ }
+
+ return IIO_VAL_FRACTIONAL;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static ssize_t as5600_reg_access_read(struct as5600_priv *priv,
+ unsigned int reg, unsigned int *val)
+{
+ int ret;
+ u8 mask;
+
+ switch (reg) {
+ case AS5600_REG_ZMCO:
+ mask = AS5600_MASK_ZMCO;
+ break;
+ case AS5600_REG_ZPOS_H:
+ mask = AS5600_MASK_ZPOS_H;
+ break;
+ case AS5600_REG_MPOS_H:
+ mask = AS5600_MASK_MPOS_H;
+ break;
+ case AS5600_REG_MANG_H:
+ mask = AS5600_MASK_MANG_H;
+ break;
+ case AS5600_REG_CONF_H:
+ mask = AS5600_MASK_CONF_H;
+ break;
+ case AS5600_REG_STATUS:
+ mask = AS5600_MASK_STATUS;
+ break;
+ case AS5600_REG_RAW_ANGLE_H:
+ mask = AS5600_MASK_RAW_ANGLE_H;
+ break;
+ case AS5600_REG_ANGLE_H:
+ mask = AS5600_MASK_ANGLE_H;
+ break;
+ case AS5600_REG_MAGN_H:
+ mask = AS5600_MASK_MAGN_H;
+ break;
+ case AS5600_REG_ZPOS_L:
+ case AS5600_REG_MPOS_L:
+ case AS5600_REG_MANG_L:
+ case AS5600_REG_CONF_L:
+ case AS5600_REG_RAW_ANGLE_L:
+ case AS5600_REG_ANGLE_L:
+ case AS5600_REG_AGC:
+ case AS5600_REG_MAGN_L:
+ mask = 0xFF;
+ break;
+ default:
+ /* Not a readable register */
+ return -EINVAL;
+ }
+
+
+ ret = i2c_smbus_read_byte_data(priv->client, reg);
+ if (ret < 0)
+ return ret;
+
+ /* because the chip may return garbage data in the unused bits */
+ *val = ret & mask;
+ return 0;
+}
+
+static ssize_t as5600_reg_access_write(struct as5600_priv *priv,
+ unsigned int reg, unsigned int writeval)
+{
+ int ret;
+ u8 mask;
+
+ if (writeval > 0xFF)
+ return -EINVAL;
+
+ switch (reg) {
+ case AS5600_REG_ZPOS_H:
+ mask = AS5600_MASK_ZPOS_H;
+ break;
+ case AS5600_REG_MPOS_H:
+ mask = AS5600_MASK_MPOS_H;
+ break;
+ case AS5600_REG_MANG_H:
+ mask = AS5600_MASK_MANG_H;
+ break;
+ case AS5600_REG_CONF_H:
+ mask = AS5600_MASK_CONF_H;
+ break;
+ case AS5600_REG_ZPOS_L:
+ case AS5600_REG_MPOS_L:
+ case AS5600_REG_MANG_L:
+ case AS5600_REG_CONF_L:
+ case AS5600_REG_BURN:
+ mask = 0xFF;
+ break;
+ default:
+ /* Not a writable register */
+ return -EINVAL;
+ }
+
+ ret = i2c_smbus_write_byte_data(priv->client, reg, writeval & mask);
+ if (ret < 0)
+ return ret;
+
+ /* update priv->zpos and priv->mpos */
+ mutex_lock(&priv->lock);
+ switch (reg) {
+ case AS5600_REG_ZPOS_H:
+ priv->zpos = (priv->zpos & 0x00FF) | ((writeval & mask) << 8);
+ break;
+ case AS5600_REG_ZPOS_L:
+ priv->zpos = (priv->zpos & 0xFF00) | (writeval & mask);
+ break;
+ case AS5600_REG_MPOS_H:
+ priv->mpos = (priv->mpos & 0x00FF) | ((writeval & mask) << 8);
+ break;
+ case AS5600_REG_MPOS_L:
+ priv->mpos = (priv->mpos & 0xFF00) | (writeval & mask);
+ break;
+ }
+ mutex_unlock(&priv->lock);
+ return 0;
+}
+
+static int as5600_reg_access(struct iio_dev *indio_dev, unsigned int reg,
+ unsigned int writeval, unsigned int *readval)
+{
+ struct as5600_priv *priv = iio_priv(indio_dev);
+ int ret;
+
+ if (readval) {
+ ret = as5600_reg_access_read(priv, reg, readval);
+ } else {
+ ret = as5600_reg_access_write(priv, reg, writeval);
+ }
+
+ return ret;
+}
+
+static const struct iio_chan_spec as5600_channels[] = {
+ {
+ .type = IIO_ANGL,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ .indexed = 1,
+ .channel = 0,
+ },
+ {
+ .type = IIO_ANGL,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ .indexed = 1,
+ .channel = 1,
+ },
+};
+
+static const struct iio_info as5600_info = {
+ .read_raw = &as5600_read_raw,
+ .debugfs_reg_access = &as5600_reg_access,
+};
+
+static int as5600_probe(struct i2c_client *client)
+{
+ struct as5600_priv *priv;
+ struct iio_dev *indio_dev;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*priv));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ priv = iio_priv(indio_dev);
+ i2c_set_clientdata(client, indio_dev);
+ priv->client = client;
+ mutex_init(&priv->lock);
+
+ indio_dev->info = &as5600_info;
+ indio_dev->name = "as5600";
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = as5600_channels;
+ indio_dev->num_channels = ARRAY_SIZE(as5600_channels);
+
+ ret = i2c_smbus_read_byte_data(client, AS5600_REG_STATUS);
+ if (ret < 0)
+ return ret;
+
+ /* No magnet present could be a problem. */
+ if ((ret & AS5600_MASK_MD) == 0)
+ dev_warn(&client->dev, "Magnet not detected\n");
+
+ ret = i2c_smbus_read_word_swapped(client, AS5600_REG_ZPOS);
+ if (ret < 0)
+ return ret;
+ priv->zpos = ret & AS5600_FIELD_ZPOS;
+
+ ret = i2c_smbus_read_word_swapped(client, AS5600_REG_MPOS);
+ if (ret < 0)
+ return ret;
+ priv->mpos = ret & AS5600_FIELD_MPOS;
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id as5600_id[] = {
+ { "as5600" },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, as5600_id);
+
+static const struct of_device_id as5600_match[] = {
+ { .compatible = "ams,as5600" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, as5600_match);
+
+static struct i2c_driver as5600_driver = {
+ .driver = {
+ .name = "as5600",
+ .of_match_table = as5600_match,
+ },
+ .probe = as5600_probe,
+ .id_table = as5600_id,
+};
+
+module_i2c_driver(as5600_driver);
+
+MODULE_AUTHOR("Frank Zago <frank@...o.net>");
+MODULE_AUTHOR("Aditya Dutt <duttaditya18@...il.com>");
+MODULE_DESCRIPTION("ams AS5600 Position Sensor");
+MODULE_LICENSE("GPL");
--
2.34.1
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