[PATCH v3 0/2] iio: magnetometer: add MEMSIC MMC5983MA driver

[PATCH v3 0/2] iio: magnetometer: add MEMSIC MMC5983MA driver

[Vladislav Kulikov]

Add an IIO driver for the MEMSIC MMC5983MA 3-axis magnetometer over
I2C. The driver provides raw magnetic field readings with
per-measurement SET/RESET offset cancellation, giving 18-bit output
with a full-scale range of +/-8 Gauss.

MMC5983MA is not register-compatible with the existing MEMSIC
magnetometer drivers. It has a different register map, 18-bit output
data format, and I2C/SPI transport support.

Tested on a Raspberry Pi 2B with the sensor on I2C-1 at 0x30.

The initial driver implements the validated I2C single-measurement path.
Other chip features are left for future work:

- SPI transport: the binding describes SPI wiring, but driver support is
  left for follow-up validation of the SPI command and SET/RESET
  sequencing.
- Temperature channel: left until the temperature output behavior is
  better validated.
- Continuous measurement mode and Auto SET/RESET: left until the
  interaction between CMM, TM_M, Meas_M_Done, and SET/RESET sequencing
  is better understood.
- Saturation/self-test bits and BW/decimation tuning: not exposed until
  their behavior can be described reliably through stable IIO ABI.

The driver uses a conservative 500 us post-SET/RESET delay before
starting the following measurement. The datasheet describes a 500 ns
SET/RESET coil pulse, but testing showed that a longer software delay is
needed before taking the next measurement.

Changes since v2:
- Driver:
  - refactored SET/RESET coil pulse into mmc5983_pulse_coil() helper
  - used USEC_PER_MSEC for regmap_read_poll_timeout and fsleep constants
- DT binding:
  - removed redundant comments from examples
- Cover letter:
  - added "why a new driver" explanation
- Collected Reviewed-by and Acked-by tags

Changes since v1:
- DT binding:
  - added SPI bus support, interrupts, and vddio-supply
  - made vdd-supply required
  - switched to unevaluatedProperties with spi-peripheral-props ref
- Driver:
  - replaced scoped_guard() with guard(mutex) in a case block
  - added datasheet page references for timing values
  - changed product ID mismatch from probe failure to dev_info()
  - hardcoded the IIO device name
  - added trailing commas
  - added local struct device and regmap pointers in mmc5983_init()
- MAINTAINERS:
  - split binding and driver F: entries across the relevant patches

Vladislav Kulikov (2):
  dt-bindings: iio: magnetometer: add MEMSIC MMC5983MA
  iio: magnetometer: add driver for MEMSIC MMC5983MA

 .../iio/magnetometer/memsic,mmc5983.yaml      |  63 ++++
 MAINTAINERS                                   |   7 +
 drivers/iio/magnetometer/Kconfig              |  11 +
 drivers/iio/magnetometer/Makefile             |   1 +
 drivers/iio/magnetometer/mmc5983.c            | 345 ++++++++++++++++++
 5 files changed, 427 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml
 create mode 100644 drivers/iio/magnetometer/mmc5983.c


base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32
-- 
2.43.0

[PATCH v3 1/2] dt-bindings: iio: magnetometer: add MEMSIC MMC5983MA

[Vladislav Kulikov]

Add a Devicetree binding for the MEMSIC MMC5983MA 3-axis
magnetometer.

MMC5983MA is not register-compatible with the existing MEMSIC
magnetometer drivers. It has a different register map, 18-bit output
data format, and I2C/SPI transport support.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Vladislav Kulikov <vlad.kulikov.c@gmail.com>
---
 .../iio/magnetometer/memsic,mmc5983.yaml      | 63 +++++++++++++++++++
 MAINTAINERS                                   |  6 ++
 2 files changed, 69 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml

diff --git a/Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml b/Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml
new file mode 100644
index 000000000000..4a4df6bb70fe
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/magnetometer/memsic,mmc5983.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MEMSIC MMC5983MA 3-axis magnetic sensor
+
+maintainers:
+  - Vladislav Kulikov <vlad.kulikov.c@gmail.com>
+
+properties:
+  compatible:
+    const: memsic,mmc5983
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  vdd-supply:
+    description: Regulator that provides power to the sensor
+
+  vddio-supply:
+    description: Regulator that provides power to the digital interface and INT pin
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        magnetometer@30 {
+            compatible = "memsic,mmc5983";
+            reg = <0x30>;
+            vdd-supply = <&vdd_3v3_reg>;
+            vddio-supply = <&vdd_3v3_reg>;
+        };
+    };
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        magnetometer@0 {
+            compatible = "memsic,mmc5983";
+            reg = <0>;
+            spi-max-frequency = <10000000>;
+            vdd-supply = <&vdd_3v3_reg>;
+            vddio-supply = <&vdd_3v3_reg>;
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 882214b0e7db..952fbf3020a4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17170,6 +17170,12 @@ F:	drivers/mtd/
 F:	include/linux/mtd/
 F:	include/uapi/mtd/
 
+MEMSIC MMC5983 MAGNETOMETER DRIVER
+M:	Vladislav Kulikov <vlad.kulikov.c@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml
+
 MEN A21 WATCHDOG DRIVER
 M:	Johannes Thumshirn <morbidrsa@gmail.com>
 L:	linux-watchdog@vger.kernel.org
-- 
2.43.0

[PATCH v3 2/2] iio: magnetometer: add driver for MEMSIC MMC5983MA

[Vladislav Kulikov]

Add support for the MEMSIC MMC5983MA 3-axis magnetometer. The driver
provides raw magnetic field readings via IIO sysfs with SET/RESET
offset cancellation for each measurement.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Vladislav Kulikov <vlad.kulikov.c@gmail.com>
---
 MAINTAINERS                        |   1 +
 drivers/iio/magnetometer/Kconfig   |  11 +
 drivers/iio/magnetometer/Makefile  |   1 +
 drivers/iio/magnetometer/mmc5983.c | 345 +++++++++++++++++++++++++++++
 4 files changed, 358 insertions(+)
 create mode 100644 drivers/iio/magnetometer/mmc5983.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 952fbf3020a4..b1d9d7b586a1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17175,6 +17175,7 @@ M:	Vladislav Kulikov <vlad.kulikov.c@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/magnetometer/memsic,mmc5983.yaml
+F:	drivers/iio/magnetometer/mmc5983.c
 
 MEN A21 WATCHDOG DRIVER
 M:	Johannes Thumshirn <morbidrsa@gmail.com>
diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
index fb313e591e85..ea2697fb5ab6 100644
--- a/drivers/iio/magnetometer/Kconfig
+++ b/drivers/iio/magnetometer/Kconfig
@@ -151,6 +151,17 @@ config MMC5633
 	  To compile this driver as a module, choose M here: the module
 	  will be called mmc5633
 
+config MMC5983
+	tristate "MEMSIC MMC5983 3-axis magnetic sensor"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say yes here to build support for the MEMSIC MMC5983 3-axis
+	  magnetic sensor.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called mmc5983
+
 config IIO_ST_MAGN_3AXIS
 	tristate "STMicroelectronics magnetometers 3-Axis Driver"
 	depends on (I2C || SPI_MASTER) && SYSFS
diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
index 5bd227f8c120..7fd9b3fd914e 100644
--- a/drivers/iio/magnetometer/Makefile
+++ b/drivers/iio/magnetometer/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_MAG3110)	+= mag3110.o
 obj-$(CONFIG_HID_SENSOR_MAGNETOMETER_3D) += hid-sensor-magn-3d.o
 obj-$(CONFIG_MMC35240)	+= mmc35240.o
 obj-$(CONFIG_MMC5633)	+= mmc5633.o
+obj-$(CONFIG_MMC5983)	+= mmc5983.o
 
 obj-$(CONFIG_IIO_ST_MAGN_3AXIS) += st_magn.o
 st_magn-y := st_magn_core.o
diff --git a/drivers/iio/magnetometer/mmc5983.c b/drivers/iio/magnetometer/mmc5983.c
new file mode 100644
index 000000000000..400406c824d7
--- /dev/null
+++ b/drivers/iio/magnetometer/mmc5983.c
@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MMC5983 - MEMSIC 3-axis Magnetic Sensor
+ *
+ * Copyright (c) 2026, Vlad Kulikov <vlad.kulikov.c@gmail.com>
+ *
+ * IIO driver for MMC5983
+ */
+
+#include <linux/bits.h>
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/time.h>
+#include <linux/types.h>
+
+#define MMC5983_REG_XOUT0	0x00
+#define MMC5983_REG_XOUT1	0x01
+#define MMC5983_REG_YOUT0	0x02
+#define MMC5983_REG_YOUT1	0x03
+#define MMC5983_REG_ZOUT0	0x04
+#define MMC5983_REG_ZOUT1	0x05
+#define MMC5983_REG_XYZOUT2	0x06
+
+#define MMC5983_REG_STATUS	0x08
+
+#define MMC5983_REG_CTRL0	0x09
+#define MMC5983_REG_CTRL1	0x0A
+#define MMC5983_REG_CTRL2	0x0B
+#define MMC5983_REG_CTRL3	0x0C
+
+#define MMC5983_REG_ID		0x2F
+
+#define MMC5983_PRODUCT_ID	0x30
+
+#define MMC5983_STATUS_MEAS_M_DONE_BIT	BIT(0)
+#define MMC5983_STATUS_OTP_RD_DONE_BIT	BIT(4)
+
+#define MMC5983_CTRL0_TM_M_BIT		BIT(0)
+#define MMC5983_CTRL0_SET_BIT		BIT(3)
+#define MMC5983_CTRL0_RESET_BIT		BIT(4)
+#define MMC5983_CTRL0_OTP_RD_BIT	BIT(6)
+
+#define MMC5983_CTRL1_SW_RST_BIT	BIT(7)
+
+enum mmc5983_axis {
+	MMC5983_AXIS_X,
+	MMC5983_AXIS_Y,
+	MMC5983_AXIS_Z,
+};
+
+struct mmc5983_data {
+	struct regmap *regmap;
+	/* Protects chip access during SET/RESET measurement sequence */
+	struct mutex mutex;
+};
+
+#define MMC5983_CHANNEL(_axis) { \
+	.type = IIO_MAGN, \
+	.modified = 1, \
+	.channel2 = IIO_MOD_##_axis, \
+	.address = MMC5983_AXIS_##_axis, \
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec mmc5983_channels[] = {
+	MMC5983_CHANNEL(X),
+	MMC5983_CHANNEL(Y),
+	MMC5983_CHANNEL(Z),
+};
+
+static int mmc5983_pulse_coil(struct mmc5983_data *data, unsigned int coil_bit)
+{
+	int ret;
+
+	ret = regmap_write(data->regmap, MMC5983_REG_CTRL0, coil_bit);
+	if (ret)
+		return ret;
+
+	/*
+	 * Datasheet page 15: SET/RESET coil pulse is 500 ns.
+	 * Vendor sample code waits 500 us before the next operation.
+	 */
+	fsleep(500);
+
+	return 0;
+}
+
+static int mmc5983_take_measurement(struct mmc5983_data *data, int m[3])
+{
+	unsigned int status;
+	u8 buf[7];
+	int ret;
+
+	ret = regmap_write(data->regmap, MMC5983_REG_CTRL0,
+			   MMC5983_CTRL0_TM_M_BIT);
+	if (ret)
+		return ret;
+
+	/*
+	 * Datasheet page 15: measurement time is 8 ms at BW=00 (default,
+	 * slowest setting). Use a 50 ms timeout for margin.
+	 */
+	ret = regmap_read_poll_timeout(data->regmap, MMC5983_REG_STATUS,
+				       status,
+				       status & MMC5983_STATUS_MEAS_M_DONE_BIT,
+				       10 * USEC_PER_MSEC,
+				       50 * USEC_PER_MSEC);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, MMC5983_REG_XOUT0, buf,
+			       sizeof(buf));
+	if (ret)
+		return ret;
+
+	m[0] = (buf[0] << 10) | (buf[1] << 2) | ((buf[6] >> 6) & 0x3);
+	m[1] = (buf[2] << 10) | (buf[3] << 2) | ((buf[6] >> 4) & 0x3);
+	m[2] = (buf[4] << 10) | (buf[5] << 2) | ((buf[6] >> 2) & 0x3);
+
+	return 0;
+}
+
+static int mmc5983_read_raw(struct iio_dev *indio_dev,
+			     const struct iio_chan_spec *chan, int *val,
+			     int *val2, long mask)
+{
+	struct mmc5983_data *data = iio_priv(indio_dev);
+	int m1[3], m2[3];
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW: {
+		guard(mutex)(&data->mutex);
+
+		/* SET: magnetize sensor elements in forward direction */
+		ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_SET_BIT);
+		if (ret)
+			return ret;
+
+		ret = mmc5983_take_measurement(data, m1);
+		if (ret)
+			return ret;
+
+		/* RESET: magnetize sensor elements in reverse direction */
+		ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_RESET_BIT);
+		if (ret)
+			return ret;
+
+		ret = mmc5983_take_measurement(data, m2);
+		if (ret)
+			return ret;
+
+		*val = (m1[chan->address] - m2[chan->address]) / 2;
+		return IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = 61035;
+		return IIO_VAL_INT_PLUS_NANO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info mmc5983_info = {
+	.read_raw = mmc5983_read_raw,
+};
+
+static bool mmc5983_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MMC5983_REG_CTRL0:
+	case MMC5983_REG_CTRL1:
+	case MMC5983_REG_CTRL2:
+	case MMC5983_REG_CTRL3:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool mmc5983_is_readable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MMC5983_REG_XOUT0:
+	case MMC5983_REG_XOUT1:
+	case MMC5983_REG_YOUT0:
+	case MMC5983_REG_YOUT1:
+	case MMC5983_REG_ZOUT0:
+	case MMC5983_REG_ZOUT1:
+	case MMC5983_REG_XYZOUT2:
+	case MMC5983_REG_STATUS:
+	case MMC5983_REG_CTRL0:
+	case MMC5983_REG_CTRL1:
+	case MMC5983_REG_CTRL2:
+	case MMC5983_REG_CTRL3:
+	case MMC5983_REG_ID:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool mmc5983_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MMC5983_REG_XOUT0:
+	case MMC5983_REG_XOUT1:
+	case MMC5983_REG_YOUT0:
+	case MMC5983_REG_YOUT1:
+	case MMC5983_REG_ZOUT0:
+	case MMC5983_REG_ZOUT1:
+	case MMC5983_REG_XYZOUT2:
+	case MMC5983_REG_STATUS:
+	case MMC5983_REG_CTRL0:
+	case MMC5983_REG_CTRL1:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config mmc5983_regmap_config = {
+	.name = "mmc5983_regmap",
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = MMC5983_REG_ID,
+	.writeable_reg = mmc5983_is_writeable_reg,
+	.readable_reg = mmc5983_is_readable_reg,
+	.volatile_reg = mmc5983_is_volatile_reg,
+};
+
+static int mmc5983_init(struct mmc5983_data *data)
+{
+	struct regmap *regmap = data->regmap;
+	struct device *dev = regmap_get_device(regmap);
+	unsigned int reg_id, status;
+	int ret;
+
+	ret = regmap_read(regmap, MMC5983_REG_ID, &reg_id);
+	if (ret)
+		return dev_err_probe(dev, ret, "Error reading product id\n");
+
+	if (reg_id != MMC5983_PRODUCT_ID)
+		dev_info(dev, "unexpected product id 0x%02x\n", reg_id);
+
+	ret = regmap_write(regmap, MMC5983_REG_CTRL1, MMC5983_CTRL1_SW_RST_BIT);
+	if (ret)
+		return ret;
+
+	/* Datasheet page 15: power-on time after SW_RST is 10 ms */
+	fsleep(10 * USEC_PER_MSEC);
+
+	ret = regmap_write(regmap, MMC5983_REG_CTRL0, MMC5983_CTRL0_OTP_RD_BIT);
+	if (ret)
+		return ret;
+
+	/*
+	 * Datasheet page 15: OTP read completes and self-clears. No separate
+	 * OTP refresh timeout is specified, so use the 10 ms power-on time as
+	 * a conservative upper bound.
+	 */
+	ret = regmap_read_poll_timeout(regmap, MMC5983_REG_STATUS, status,
+				       status & MMC5983_STATUS_OTP_RD_DONE_BIT,
+				       USEC_PER_MSEC,
+				       10 * USEC_PER_MSEC);
+	if (ret)
+		return ret;
+
+	/* SET: magnetize sensor elements in forward direction */
+	ret = mmc5983_pulse_coil(data, MMC5983_CTRL0_SET_BIT);
+	if (ret)
+		return ret;
+
+	/* RESET: magnetize sensor elements in reverse direction */
+	return mmc5983_pulse_coil(data, MMC5983_CTRL0_RESET_BIT);
+}
+
+static int mmc5983_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct mmc5983_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+
+	ret = devm_mutex_init(dev, &data->mutex);
+	if (ret)
+		return ret;
+
+	data->regmap = devm_regmap_init_i2c(i2c, &mmc5983_regmap_config);
+	if (IS_ERR(data->regmap))
+		return dev_err_probe(dev, PTR_ERR(data->regmap),
+				     "failed to allocate register map\n");
+
+	indio_dev->info = &mmc5983_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->name = "mmc5983";
+	indio_dev->channels = mmc5983_channels;
+	indio_dev->num_channels = ARRAY_SIZE(mmc5983_channels);
+
+	ret = mmc5983_init(data);
+	if (ret)
+		return dev_err_probe(dev, ret, "mmc5983 chip init failed\n");
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id mmc5983_of_match[] = {
+	{ .compatible = "memsic,mmc5983" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mmc5983_of_match);
+
+static const struct i2c_device_id mmc5983_id[] = {
+	{ "mmc5983" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mmc5983_id);
+
+static struct i2c_driver mmc5983_driver = {
+	.driver = {
+		.name = "mmc5983",
+		.of_match_table = mmc5983_of_match,
+	},
+	.probe = mmc5983_probe,
+	.id_table = mmc5983_id,
+};
+module_i2c_driver(mmc5983_driver);
+
+MODULE_AUTHOR("Vladislav Kulikov <vlad.kulikov.c@gmail.com>");
+MODULE_DESCRIPTION("MEMSIC MMC5983 magnetic sensor driver");
+MODULE_LICENSE("GPL");
-- 
2.43.0