[PATCH v2] iio: position: Add support for ams AS5600 angle sensor
From: frank zago
Date: Sat Dec 25 2021 - 12:54:01 EST
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 various registers through debugfs for further configuration.
Signed-off-by: frank zago <frank@xxxxxxxx>
---
changes in v2
- set the scale for both channels
- moved the sysfs entries into debugfs
- add enums for each register fields
- add rst doc for the driver
Documentation/iio/as5600.rst | 143 ++++++++++++++
Documentation/iio/index.rst | 2 +
drivers/iio/position/Kconfig | 10 +
drivers/iio/position/Makefile | 1 +
drivers/iio/position/as5600.c | 350 ++++++++++++++++++++++++++++++++++
5 files changed, 506 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..4f672baa78b6
--- /dev/null
+++ b/Documentation/iio/as5600.rst
@@ -0,0 +1,143 @@
+.. 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.com/documents/20143/36005/AS5600_DS000365_5-00.pdf
+
+
+Accessing the device registers
+==============================
+
+If needed, the device can be configured through debugfs, where most
+register fields are accessible.
+
+.. flat-table:: Registers and fields
+
+ * - Register
+ - Field
+ - Index
+ - Writable range
+
+ * - ZMCO
+ - ZMCO
+ - 0
+
+ * - ZPOS
+ - ZPOS
+ - 1
+ - 0 to 4095
+
+ * - MPOS
+ - MPOS
+ - 2
+ - 0 to 4095
+
+ * - MANG
+ - MANG
+ - 3
+
+ * - CONF
+ - PM
+ - 4
+ - 0 to 3
+
+ * - CONF
+ - HYST
+ - 5
+ - 0 to 3
+
+ * - CONF
+ - OUTS
+ - 6
+ - 0 to 3
+
+ * - CONF
+ - PWMF
+ - 7
+ - 0 to 3
+
+ * - CONF
+ - SF
+ - 8
+ - 0 to 3
+
+ * - CONF
+ - FTH
+ - 9
+ - 0 to 7
+
+ * - CONF
+ - WD
+ - 10
+ - 0 or 1
+
+ * - STATUS
+ - MH
+ - 11
+
+ * - STATUS
+ - ML
+ - 12
+
+ * - STATUS
+ - MD
+ - 13
+
+ * - AGC
+ - AGC
+ - 14
+
+ * - MAGNITUDE
+ - MAGNITUDE
+ - 15
+
+These registers allow the user to check the device and, if needed, to
+configure it.
+
+Assuming the device is iio:device0, its debugfs path will be::
+
+ AS5600=/sys/kernel/debug/iio/iio:device0/direct_reg_access
+
+Locate the index of a register to access in the table above, then use
+the following commands to read a value::
+
+ $ echo <index> > $AS5600/direct_reg_access
+ $ cat $AS5600/direct_reg_access
+
+or this to write a value::
+
+ $ echo <index> <value> > $AS5600/direct_reg_access
+
+For instance, this would return 1 if the magnet is present::
+
+ $ echo 13 > $AS5600/direct_reg_access
+ $ cat $AS5600/direct_reg_access
+
+
+Channels
+========
+
+The driver provides 2 channels. The channel 0 returns the raw,
+unscaled data. The channel 1 returns the data as was scaled by the
+device when ZPOS / MPOS are used. All angles returned have a value of
+0 to 4095.
+
+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. For instance,
+this sets ZPOS and MPOS to a 70 degrees angle (4096/360*70=796), starting
+at some given offset (1200)::
+
+ echo 1 1200 > $AS5600
+ echo 2 1996 > $AS5600
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 58b7a4ebac51..937b626e64d4 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -9,4 +9,6 @@ Industrial I/O
iio_configfs
+ as5600
+
ep93xx_adc
diff --git a/drivers/iio/position/Kconfig b/drivers/iio/position/Kconfig
index 1576a6380b53..111ed551ae79 100644
--- a/drivers/iio/position/Kconfig
+++ b/drivers/iio/position/Kconfig
@@ -6,6 +6,16 @@
menu "Linear and angular position sensors"
+config AS5600
+ tristate "ams AS5600 angular position sensor"
+ depends on I2C
+ help
+ Say Y here if you want to build support for the ams 5600
+ 12-Bit Programmable Contactless Potentiometer.
+
+ To compile this driver as a module, choose M here: the module
+ will be called as5600.
+
config IQS624_POS
tristate "Azoteq IQS624/625 angular position sensors"
depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/iio/position/Makefile b/drivers/iio/position/Makefile
index d70902f2979d..53930681e6a4 100644
--- a/drivers/iio/position/Makefile
+++ b/drivers/iio/position/Makefile
@@ -4,5 +4,6 @@
# When adding new entries keep the list in alphabetical order
+obj-$(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..2c45dbfe170d
--- /dev/null
+++ b/drivers/iio/position/as5600.c
@@ -0,0 +1,350 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ams AS5600 -- 12-Bit Programmable Contactless Potentiometer
+ *
+ * Copyright 2021, Frank Zago
+ *
+ * datasheet v1.06 (2018-Jun-20):
+ * https://ams.com/documents/20143/36005/AS5600_DS000365_5-00.pdf
+ *
+ * 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.
+ *
+ * Permanent programming of the MPOS/ZPOS/MANG/CONF registers is not
+ * implemented.
+ *
+ * The i2c address of the device is 0x36.
+ */
+
+#include <linux/iio/iio.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/bitfield.h>
+
+/* Registers and their fields, as defined in the datasheet */
+#define REG_ZMCO 0x00
+#define REG_ZPOS 0x01
+#define REG_ZPOS_ZPOS GENMASK(11, 0)
+#define REG_MPOS 0x03
+#define REG_MPOS_MPOS GENMASK(11, 0)
+#define REG_MANG 0x05
+#define REG_MANG_MANG GENMASK(11, 0)
+#define REG_CONF 0x07
+#define REG_STATUS 0x0b
+#define REG_STATUS_MD BIT(5)
+#define REG_RAW_ANGLE 0x0c
+#define REG_RAW_ANGLE_ANGLE GENMASK(11, 0)
+#define REG_ANGLE 0x0e
+#define REG_ANGLE_ANGLE GENMASK(11, 0)
+#define REG_AGC 0x1a
+#define REG_MAGNITUDE 0x1b
+#define REG_BURN 0xff
+
+enum {
+ X_REG_ZMCO_ZMCO,
+ X_REG_ZPOS_ZPOS,
+ X_REG_MPOS_MPOS,
+ X_REG_MANG_MANG,
+ X_REG_CONF_PM,
+ X_REG_CONF_HYST,
+ X_REG_CONF_OUTS,
+ X_REG_CONF_PWMF,
+ X_REG_CONF_SF,
+ X_REG_CONF_FTH,
+ X_REG_CONF_WD,
+ X_REG_STATUS_MH,
+ X_REG_STATUS_ML,
+ X_REG_STATUS_MD,
+ X_REG_AGC_AGC,
+ X_REG_MAGNITUDE_MAGNITUDE,
+
+ X_REG_NUM_ENTRIES, /* last */
+};
+
+static const struct {
+ u8 reg;
+ u16 mask;
+ u16 max_value; /* maximum writable value */
+} reg_access[] = {
+ [X_REG_ZMCO_ZMCO] = { REG_ZMCO, GENMASK(1, 0) },
+ [X_REG_ZPOS_ZPOS] = { REG_ZPOS, REG_ZPOS_ZPOS, 4095 },
+ [X_REG_MPOS_MPOS] = { REG_MPOS, REG_MPOS_MPOS, 4095 },
+ [X_REG_MANG_MANG] = { REG_MANG, REG_MANG_MANG, 4095 },
+ [X_REG_CONF_PM] = { REG_CONF, GENMASK(1, 0), 3 },
+ [X_REG_CONF_HYST] = { REG_CONF, GENMASK(3, 2), 3 },
+ [X_REG_CONF_OUTS] = { REG_CONF, GENMASK(5, 4), 3 },
+ [X_REG_CONF_PWMF] = { REG_CONF, GENMASK(7, 6), 3 },
+ [X_REG_CONF_SF] = { REG_CONF, GENMASK(9, 8), 3 },
+ [X_REG_CONF_FTH] = { REG_CONF, GENMASK(12, 10), 7},
+ [X_REG_CONF_WD] = { REG_CONF, BIT(13), 1 },
+ [X_REG_STATUS_MH] = { REG_STATUS, BIT(3) },
+ [X_REG_STATUS_ML] = { REG_STATUS, BIT(4) },
+ [X_REG_STATUS_MD] = { REG_STATUS, REG_STATUS_MD },
+ [X_REG_AGC_AGC] = { REG_AGC, GENMASK(7, 0) },
+ [X_REG_MAGNITUDE_MAGNITUDE] = { REG_MAGNITUDE, GENMASK(11, 0) },
+};
+
+/* runtime versions of the FIELD_GET/FIELD_PREP macros */
+#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
+#define field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
+
+struct as5600_priv {
+ struct iio_dev *iio_dev;
+ 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 angle;
+ u16 reg;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ if (chan->channel == 0) {
+ reg = REG_RAW_ANGLE;
+ bitmask = REG_RAW_ANGLE_ANGLE;
+ } else {
+ reg = REG_ANGLE;
+ bitmask = REG_ANGLE_ANGLE;
+ }
+ angle = i2c_smbus_read_word_swapped(priv->client, reg);
+
+ if (angle < 0)
+ return angle;
+ *val = field_get(bitmask, angle);
+
+ 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 = 3141592;
+ *val2 = 2048000000;
+ } else {
+ s32 range;
+
+ /* 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 * 314159;
+ *val /= 4096;
+ *val2 = 204800000;
+ }
+
+ return IIO_VAL_FRACTIONAL;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static ssize_t as5600_reg_access_read(struct as5600_priv *priv,
+ unsigned int reg_access_idx,
+ unsigned int *readval)
+{
+ unsigned int reg = reg_access[reg_access_idx].reg;
+ unsigned int mask = reg_access[reg_access_idx].mask;
+ int ret;
+
+ switch (reg) {
+ case REG_ZMCO:
+ case REG_STATUS:
+ case REG_AGC:
+ ret = i2c_smbus_read_byte_data(priv->client, reg);
+ if (ret < 0)
+ return ret;
+
+ *readval = field_get(mask, ret);
+ return 0;
+
+ case REG_ZPOS:
+ case REG_MPOS:
+ case REG_CONF:
+ case REG_MAGNITUDE:
+ ret = i2c_smbus_read_word_swapped(priv->client, reg);
+ if (ret < 0)
+ return ret;
+
+ *readval = field_get(mask, ret);
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+static ssize_t as5600_reg_access_write(struct as5600_priv *priv,
+ unsigned int reg_access_idx,
+ unsigned int writeval)
+{
+ unsigned int reg = reg_access[reg_access_idx].reg;
+ unsigned int mask = reg_access[reg_access_idx].mask;
+ u16 out;
+ int ret;
+
+ switch (reg) {
+ case REG_ZPOS:
+ case REG_MPOS:
+ case REG_CONF:
+ if (writeval > reg_access[reg_access_idx].max_value)
+ return -EINVAL;
+
+ /* Read then write, as per spec */
+ ret = i2c_smbus_read_word_swapped(priv->client, reg);
+ if (ret < 0)
+ return ret;
+
+ out = ret & ~mask;
+ out |= field_prep(mask, writeval);
+
+ ret = i2c_smbus_write_word_swapped(priv->client, reg, out);
+ if (ret < 0)
+ return ret;
+
+ if (reg == REG_ZPOS)
+ priv->zpos = writeval;
+ else if (reg == REG_MPOS)
+ priv->mpos = writeval;
+
+ break;
+
+ default:
+ /* Not a writable register */
+ return -EINVAL;
+
+ }
+
+ 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 (reg >= X_REG_NUM_ENTRIES)
+ return -EINVAL;
+
+ if (readval) {
+ ret = as5600_reg_access_read(priv, reg, readval);
+ } else {
+
+ mutex_lock(&priv->lock);
+ ret = as5600_reg_access_write(priv, reg, writeval);
+ mutex_unlock(&priv->lock);
+ }
+
+ 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,
+ const struct i2c_device_id *id)
+{
+ 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, REG_STATUS);
+ if (ret < 0)
+ return ret;
+
+ /* No magnet present could be a problem. */
+ if ((ret & REG_STATUS_MD) == 0)
+ dev_warn(&client->dev, "Magnet not detected\n");
+
+ ret = i2c_smbus_read_byte_data(client, REG_ZPOS);
+ if (ret < 0)
+ return ret;
+ priv->zpos = FIELD_GET(REG_ZPOS_ZPOS, ret);
+
+ ret = i2c_smbus_read_byte_data(client, REG_MPOS);
+ if (ret < 0)
+ return ret;
+ priv->mpos = FIELD_GET(REG_MPOS_MPOS, ret);
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id as5600_i2c_id[] = {
+ {"as5600", 0},
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, as5600_i2c_id);
+
+static struct i2c_driver as5600_driver = {
+ .driver = {
+ .name = "as5600_i2c",
+ },
+ .probe = as5600_probe,
+ .id_table = as5600_i2c_id,
+};
+
+module_i2c_driver(as5600_driver);
+
+MODULE_AUTHOR("Frank Zago <frank@xxxxxxxx>");
+MODULE_DESCRIPTION("ams AS5600 Contactless Potentiometer");
+MODULE_LICENSE("GPL");
--
2.32.0