[PATCH 0/2] iio: magnetometer: add support for Si7210

[PATCH 0/2] iio: magnetometer: add support for Si7210

[Antoni Pokusinski]

This patch series adds support for the Si7210 Hall effect I2C sensor.
The driver currently supports the basic functionalities (i.e. making
temperature and magnetic field measurements and changing the
measurements scale) but I plan to add support for some other features in
the future as well (e.g. the digital output interrupt).

Antoni Pokusinski (2):
  dt-bindings: iio: magnetometer: add binding for Si7210
  iio: magnetometer: si7210: add driver for Si7210

 .../iio/magnetometer/silabs,si7210.yaml       |  44 ++
 drivers/iio/magnetometer/Kconfig              |  11 +
 drivers/iio/magnetometer/Makefile             |   2 +
 drivers/iio/magnetometer/si7210.c             | 412 ++++++++++++++++++
 4 files changed, 469 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
 create mode 100644 drivers/iio/magnetometer/si7210.c

-- 
2.45.2

[PATCH 1/2] dt-bindings: iio: magnetometer: add binding for Si7210

[Antoni Pokusinski]

Silicon Labs Si7210 is an I2C Hall effect magnetic position
and temperature sensor.

Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>
---
 .../iio/magnetometer/silabs,si7210.yaml       | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml

diff --git a/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml b/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
new file mode 100644
index 000000000000..ef29d12811e7
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/magnetometer/silabs,si7210.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Si7210 magnetic position and temperature sensor
+
+maintainers:
+  - Antoni Pokusinski <apokusinski01@gmail.com>
+
+description: |
+  Silabs Si7210 I2C Hall effect magnetic position and temperature sensor.
+  https://www.silabs.com/documents/public/data-sheets/si7210-datasheet.pdf
+
+properties:
+  compatible:
+    const: silabs,si7210
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        magnetometer@30 {
+            compatible = "silabs,si7210";
+            reg = <0x30>;
+            interrupt-parent = <&gpio1>;
+            interrupts = <4 IRQ_TYPE_EDGE_FALLING>;
+        };
+    };
-- 
2.45.2

Re: [PATCH 1/2] dt-bindings: iio: magnetometer: add binding for Si7210

[Krzysztof Kozlowski]

On Tue, Dec 31, 2024 at 02:25:12PM +0100, Antoni Pokusinski wrote:
> Silicon Labs Si7210 is an I2C Hall effect magnetic position
> and temperature sensor.
> 
> Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>
> ---
>  .../iio/magnetometer/silabs,si7210.yaml       | 44 +++++++++++++++++++
>  1 file changed, 44 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml b/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
> new file mode 100644
> index 000000000000..ef29d12811e7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/magnetometer/silabs,si7210.yaml
> @@ -0,0 +1,44 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/magnetometer/silabs,si7210.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Si7210 magnetic position and temperature sensor
> +
> +maintainers:
> +  - Antoni Pokusinski <apokusinski01@gmail.com>
> +
> +description: |
> +  Silabs Si7210 I2C Hall effect magnetic position and temperature sensor.
> +  https://www.silabs.com/documents/public/data-sheets/si7210-datasheet.pdf
> +
> +properties:
> +  compatible:
> +    const: silabs,si7210
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1


You miss the vdd-supply, because otherwise it would fit into
trivial-devices.

Best regards,
Krzysztof

[PATCH 2/2] iio: magnetometer: si7210: add driver for Si7210

[Antoni Pokusinski]

Silicon Labs Si7210 is an I2C Hall effect magnetic position and
temperature sensor. The driver supports the following functionalities:
* reading the temperature measurements
* reading the magnetic field measurements in a single-shot mode
* choosing the magnetic field measurement scale (20 or 200 mT)

Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>
---
 drivers/iio/magnetometer/Kconfig  |  11 +
 drivers/iio/magnetometer/Makefile |   2 +
 drivers/iio/magnetometer/si7210.c | 412 ++++++++++++++++++++++++++++++
 3 files changed, 425 insertions(+)
 create mode 100644 drivers/iio/magnetometer/si7210.c

diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
index 7177cd1d67cb..3debf1320ad1 100644
--- a/drivers/iio/magnetometer/Kconfig
+++ b/drivers/iio/magnetometer/Kconfig
@@ -235,6 +235,17 @@ config SENSORS_RM3100_SPI
 	  To compile this driver as a module, choose M here: the module
 	  will be called rm3100-spi.
 
+config SI7210
+	tristate "SI7210 Hall effect sensor"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say Y here to add support for the SI7210 Hall effect sensor.
+
+	  This driver can also be compiled as a module.
+	  To compile this driver as a module, choose M here: the module
+	  will be called si7210.
+
 config TI_TMAG5273
 	tristate "TI TMAG5273 Low-Power Linear 3D Hall-Effect Sensor"
 	depends on I2C
diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
index 3e4c2ecd9adf..58f32a855494 100644
--- a/drivers/iio/magnetometer/Makefile
+++ b/drivers/iio/magnetometer/Makefile
@@ -31,6 +31,8 @@ obj-$(CONFIG_SENSORS_RM3100)		+= rm3100-core.o
 obj-$(CONFIG_SENSORS_RM3100_I2C)	+= rm3100-i2c.o
 obj-$(CONFIG_SENSORS_RM3100_SPI)	+= rm3100-spi.o
 
+obj-$(CONFIG_SI7210) += si7210.o
+
 obj-$(CONFIG_TI_TMAG5273)		+= tmag5273.o
 
 obj-$(CONFIG_YAMAHA_YAS530)		+= yamaha-yas530.o
diff --git a/drivers/iio/magnetometer/si7210.c b/drivers/iio/magnetometer/si7210.c
new file mode 100644
index 000000000000..3b9b5b9807fd
--- /dev/null
+++ b/drivers/iio/magnetometer/si7210.c
@@ -0,0 +1,412 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Silicon Labs Si7210 Hall Effect sensor driver
+ *
+ * Copyright (c) 2024 Antoni Pokusinski <apokusinski01@gmail.com>
+ *
+ * Datasheet:
+ *  https://www.silabs.com/documents/public/data-sheets/si7210-datasheet.pdf
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/regmap.h>
+#include <linux/math64.h>
+#include <linux/mutex.h>
+
+/* Registers offsets and masks */
+#define SI7210_REG_DSPSIGM	0xC1
+#define SI7210_REG_DSPSIGL	0xC2
+
+#define SI7210_MASK_DSPSIGSEL	GENMASK(2, 0)
+#define SI7210_REG_DSPSIGSEL	0xC3
+
+#define SI7210_MASK_STOP	BIT(1)
+#define SI7210_MASK_ONEBURST	BIT(2)
+#define SI7210_REG_POWER_CTRL	0xC4
+
+#define SI7210_MASK_ARAUTOINC	BIT(0)
+#define SI7210_REG_ARAUTOINC	0xC5
+
+#define SI7210_REG_A0		0xCA
+#define SI7210_REG_A1		0xCB
+#define SI7210_REG_A2		0xCC
+#define SI7210_REG_A3		0xCE
+#define SI7210_REG_A4		0xCF
+#define SI7210_REG_A5		0xD0
+
+#define SI7210_REG_OTP_ADDR	0xE1
+#define SI7210_REG_OTP_DATA	0xE2
+
+#define SI7210_MASK_OTP_READ_EN	BIT(1)
+#define SI7210_REG_OTP_CTRL	0xE3
+
+/* OTP data registers offsets */
+#define SI7210_OTPREG_TMP_OFF	0x1D
+#define SI7210_OTPREG_TMP_GAIN	0x1E
+
+#define SI7210_OTPREG_A0_20	0x21
+#define SI7210_OTPREG_A1_20	0x22
+#define SI7210_OTPREG_A2_20	0x23
+#define SI7210_OTPREG_A3_20	0x24
+#define SI7210_OTPREG_A4_20	0x25
+#define SI7210_OTPREG_A5_20	0x26
+
+#define SI7210_OTPREG_A0_200	0x27
+#define SI7210_OTPREG_A1_200	0x28
+#define SI7210_OTPREG_A2_200	0x29
+#define SI7210_OTPREG_A3_200	0x2A
+#define SI7210_OTPREG_A4_200	0x2B
+#define SI7210_OTPREG_A5_200	0x2C
+
+#define A_REGS_COUNT 6
+
+static const unsigned int a20_otp_regs[A_REGS_COUNT] = {
+	SI7210_OTPREG_A0_20, SI7210_OTPREG_A1_20, SI7210_OTPREG_A2_20,
+	SI7210_OTPREG_A3_20, SI7210_OTPREG_A4_20, SI7210_OTPREG_A5_20
+};
+
+static const unsigned int a200_otp_regs[A_REGS_COUNT] = {
+	SI7210_OTPREG_A0_200, SI7210_OTPREG_A1_200, SI7210_OTPREG_A2_200,
+	SI7210_OTPREG_A3_200, SI7210_OTPREG_A4_200, SI7210_OTPREG_A5_200
+};
+
+static const struct regmap_range si7210_read_reg_ranges[] = {
+	regmap_reg_range(SI7210_REG_DSPSIGM, SI7210_REG_ARAUTOINC),
+	regmap_reg_range(SI7210_REG_A0, SI7210_REG_A2),
+	regmap_reg_range(SI7210_REG_A3, SI7210_REG_A5),
+	regmap_reg_range(SI7210_REG_OTP_ADDR, SI7210_REG_OTP_CTRL),
+};
+
+static const struct regmap_access_table si7210_readable_regs = {
+	.yes_ranges = si7210_read_reg_ranges,
+	.n_yes_ranges = ARRAY_SIZE(si7210_read_reg_ranges),
+};
+
+static const struct regmap_range si7210_write_reg_ranges[] = {
+	regmap_reg_range(SI7210_REG_DSPSIGSEL, SI7210_REG_ARAUTOINC),
+	regmap_reg_range(SI7210_REG_A0, SI7210_REG_A2),
+	regmap_reg_range(SI7210_REG_A3, SI7210_REG_A5),
+	regmap_reg_range(SI7210_REG_OTP_ADDR, SI7210_REG_OTP_CTRL),
+};
+
+static const struct regmap_access_table si7210_writeable_regs = {
+	.yes_ranges = si7210_write_reg_ranges,
+	.n_yes_ranges = ARRAY_SIZE(si7210_write_reg_ranges),
+};
+
+static const struct regmap_range si7210_volatile_reg_ranges[] = {
+	regmap_reg_range(SI7210_REG_DSPSIGM, SI7210_REG_DSPSIGL),
+	regmap_reg_range(SI7210_REG_POWER_CTRL, SI7210_REG_POWER_CTRL),
+};
+
+static const struct regmap_access_table si7210_volatile_regs = {
+	.yes_ranges = si7210_volatile_reg_ranges,
+	.n_yes_ranges = ARRAY_SIZE(si7210_volatile_reg_ranges),
+};
+
+static const struct regmap_config si7210_regmap_conf = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = SI7210_REG_OTP_CTRL,
+
+	.rd_table = &si7210_readable_regs,
+	.wr_table = &si7210_writeable_regs,
+	.volatile_table = &si7210_volatile_regs,
+};
+
+struct si7210_data {
+	struct i2c_client *client;
+	struct regmap *regmap;
+	struct mutex fetch_lock;
+	struct mutex otp_lock;
+	s8 temp_offset;
+	s8 temp_gain;
+	s8 scale_20_a[A_REGS_COUNT];
+	s8 scale_200_a[A_REGS_COUNT];
+	u8 curr_scale;
+};
+
+static const struct iio_chan_spec si7210_channels[] = {
+	{
+		.type = IIO_MAGN,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+	}
+};
+
+static int si7210_fetch_measurement(struct si7210_data *data,
+				    struct iio_chan_spec const *chan,
+				    u8 buf[2])
+{
+	u8 dspsigsel = chan->type == IIO_MAGN ? 0 : 1;
+	int ret;
+
+	scoped_guard(mutex, &data->fetch_lock) {
+		ret = regmap_update_bits(data->regmap, SI7210_REG_DSPSIGSEL,
+					 SI7210_MASK_DSPSIGSEL, dspsigsel);
+		if (ret < 0)
+			return ret;
+
+		ret = regmap_update_bits(data->regmap, SI7210_REG_POWER_CTRL,
+					 SI7210_MASK_ONEBURST | SI7210_MASK_STOP,
+					 SI7210_MASK_ONEBURST & ~SI7210_MASK_STOP);
+		if (ret < 0)
+			return ret;
+
+		/* Read the contents of the registers containing the result: DSPSIGM, DSPSIGL */
+		ret = regmap_bulk_read(data->regmap, SI7210_REG_DSPSIGM, buf, 2);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int si7210_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct si7210_data *data = iio_priv(indio_dev);
+	long long tmp;
+	u8 dspsig[2];
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = si7210_fetch_measurement(data, chan, dspsig);
+		if (ret < 0)
+			return ret;
+
+		*val = ((dspsig[0] & 0x7F) << 8) + dspsig[1];
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		if (data->curr_scale == 20)
+			*val2 = 1250;
+		else /* data->curr_scale == 200 */
+			*val2 = 12500;
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OFFSET:
+		*val = -16384;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_PROCESSED:
+		ret = si7210_fetch_measurement(data, chan, dspsig);
+		if (ret < 0)
+			return ret;
+
+		tmp = ((dspsig[0] & 0x7F) << 5) + (dspsig[1] >> 3);
+		tmp = (div_s64(-383 * tmp * tmp, 100) + (160940 * tmp - 279800000));
+		tmp = (1 + (data->temp_gain >> 11)) * tmp + 62500 * data->temp_offset;
+		tmp -= 732600;
+
+		*val = div_s64_rem(tmp, 1000000, val2);
+
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int si7210_set_scale(struct si7210_data *data, unsigned int scale)
+{
+	s8 *a_otp_values;
+	int ret;
+
+	if (scale == 20)
+		a_otp_values = data->scale_20_a;
+	else if (scale == 200)
+		a_otp_values = data->scale_200_a;
+	else
+		return -EINVAL;
+
+	scoped_guard(mutex, &data->fetch_lock) {
+		/* Write the registers 0xCA - 0xCC*/
+		ret = regmap_bulk_write(data->regmap, SI7210_REG_A0, a_otp_values, 3);
+		if (ret < 0)
+			return ret;
+
+		/* Write the registers 0xCE - 0xD0*/
+		ret = regmap_bulk_write(data->regmap, SI7210_REG_A3, &a_otp_values[3], 3);
+		if (ret < 0)
+			return ret;
+
+		data->curr_scale = scale;
+	}
+
+	return 0;
+}
+
+static int si7210_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	struct si7210_data *data = iio_priv(indio_dev);
+	unsigned int scale;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		if (val == 0 && val2 == 1250)
+			scale = 20;
+		else if (val == 0 && val2 == 12500)
+			scale = 200;
+		else
+			return -EINVAL;
+
+		return si7210_set_scale(data, scale);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int si7210_read_otpreg_val(struct si7210_data *data, unsigned int otpreg, u8 *val)
+{
+	int ret;
+	unsigned int otpdata;
+
+	scoped_guard(mutex, &data->otp_lock) {
+		ret = regmap_write(data->regmap, SI7210_REG_OTP_ADDR, otpreg);
+		if (ret < 0)
+			return ret;
+
+		ret = regmap_update_bits(data->regmap, SI7210_REG_OTP_CTRL,
+					 SI7210_MASK_OTP_READ_EN, SI7210_MASK_OTP_READ_EN);
+		if (ret < 0)
+			return ret;
+
+		ret = regmap_read(data->regmap, SI7210_REG_OTP_DATA, &otpdata);
+		if (ret < 0)
+			return ret;
+
+		*val = (u8)otpdata;
+	}
+
+	return 0;
+}
+
+static int si7210_device_wake(struct si7210_data *data)
+{
+	/* According to the datasheet, the primary method to wake up a device is
+	 *  to send an empty write. However this is not feasible using current API so we
+	 *  use the other method i.e. read a single byte. The device should respond with 0xFF
+	 */
+
+	int ret = 0;
+
+	ret = i2c_smbus_read_byte(data->client);
+	if (ret < 0)
+		return ret;
+
+	if ((u8)ret != 0xFF)
+		return -EIO;
+
+	return 0;
+}
+
+static int si7210_device_init(struct si7210_data *data)
+{
+	int ret;
+	unsigned int i;
+
+	ret = si7210_device_wake(data);
+	if (ret < 0)
+		return ret;
+
+	usleep_range(1000, 1500);
+
+	ret = si7210_read_otpreg_val(data, SI7210_OTPREG_TMP_GAIN, &data->temp_gain);
+	if (ret < 0)
+		return ret;
+	ret = si7210_read_otpreg_val(data, SI7210_OTPREG_TMP_OFF, &data->temp_offset);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < A_REGS_COUNT; i++) {
+		ret = si7210_read_otpreg_val(data, a20_otp_regs[i], &data->scale_20_a[i]);
+		if (ret < 0)
+			return ret;
+	}
+	for (i = 0; i < A_REGS_COUNT; i++) {
+		ret = si7210_read_otpreg_val(data, a200_otp_regs[i], &data->scale_200_a[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = regmap_update_bits(data->regmap, SI7210_REG_ARAUTOINC,
+				 SI7210_MASK_ARAUTOINC, SI7210_MASK_ARAUTOINC);
+	if (ret < 0)
+		return ret;
+
+	return si7210_set_scale(data, 20);
+}
+
+static const struct iio_info si7210_info = {
+	.read_raw = si7210_read_raw,
+	.write_raw = si7210_write_raw,
+};
+
+static int si7210_probe(struct i2c_client *client)
+{
+	struct si7210_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+
+	mutex_init(&data->fetch_lock);
+	mutex_init(&data->otp_lock);
+
+	data->regmap = devm_regmap_init_i2c(client, &si7210_regmap_conf);
+	if (IS_ERR(data->regmap))
+		return dev_err_probe(&client->dev, PTR_ERR(data->regmap),
+				     "failed to register regmap\n");
+
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &si7210_info;
+	indio_dev->channels = si7210_channels;
+	indio_dev->num_channels = ARRAY_SIZE(si7210_channels);
+
+	ret = si7210_device_init(data);
+	if (ret)
+		return dev_err_probe(&client->dev, ret, "device initialization failed\n");
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id si7210_id[] = {
+	{ "si7210", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si7210_id);
+
+static const struct of_device_id si7210_dt_ids[] = {
+	{ .compatible = "silabs,si7210" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, si7210_dt_ids);
+
+static struct i2c_driver si7210_driver = {
+	.driver = {
+		.name = "si7210",
+		.of_match_table = si7210_dt_ids,
+	},
+	.probe		= si7210_probe,
+	.id_table	= si7210_id,
+};
+
+module_i2c_driver(si7210_driver);
+MODULE_AUTHOR("Antoni Pokusinski <apokusinski01@gmail.com>");
+MODULE_DESCRIPTION("Silicon Labs Si7210 Hall Effect sensor I2C driver");
+MODULE_LICENSE("Dual BSD/GPL");
-- 
2.45.2

Re: [PATCH 2/2] iio: magnetometer: si7210: add driver for Si7210

[Jonathan Cameron]

On Tue, 31 Dec 2024 14:25:13 +0100
Antoni Pokusinski <apokusinski01@gmail.com> wrote:

> Silicon Labs Si7210 is an I2C Hall effect magnetic position and
> temperature sensor. The driver supports the following functionalities:
> * reading the temperature measurements
> * reading the magnetic field measurements in a single-shot mode
> * choosing the magnetic field measurement scale (20 or 200 mT)
> 
> Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>
Hi Antoni

A few comments inline. Main one is that I 'think' the scale for the
temperature is off by 1000. I got a bit lost in the maths so may have
that wrong.

Jonathan

> diff --git a/drivers/iio/magnetometer/si7210.c b/drivers/iio/magnetometer/si7210.c
> new file mode 100644
> index 000000000000..3b9b5b9807fd
> --- /dev/null
> +++ b/drivers/iio/magnetometer/si7210.c
> @@ -0,0 +1,412 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Silicon Labs Si7210 Hall Effect sensor driver
> + *
> + * Copyright (c) 2024 Antoni Pokusinski <apokusinski01@gmail.com>
> + *
> + * Datasheet:
> + *  https://www.silabs.com/documents/public/data-sheets/si7210-datasheet.pdf
> + */
> +
> +#include <linux/module.h>

Order seems a bit random.  Probably better to just go alphabetical.

> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/regmap.h>
> +#include <linux/math64.h>
> +#include <linux/mutex.h>

> +struct si7210_data {
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +	struct mutex fetch_lock;
> +	struct mutex otp_lock;
Even though somewhat obvious, each lock needs a comment on what
data it is protecting.

For the otp_lock I'm not sure you even needed as it is only used
during probe.  If that weren't the case, can you safely overlap fetch
and otp?  Is it worth that distinction, if not is one lock enough?

> +	s8 temp_offset;
> +	s8 temp_gain;
> +	s8 scale_20_a[A_REGS_COUNT];
> +	s8 scale_200_a[A_REGS_COUNT];
> +	u8 curr_scale;
> +};
> +
> +static const struct iio_chan_spec si7210_channels[] = {
> +	{
> +		.type = IIO_MAGN,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
> +	},
> +	{
> +		.type = IIO_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +	}
> +};
> +
> +static int si7210_fetch_measurement(struct si7210_data *data,
> +				    struct iio_chan_spec const *chan,
> +				    u8 buf[2])

See below. May be worth treating this as a __be16?
It is described in the datasheet as being made up of most significant
and least significant bytes so that seems a logic cleanup.

> +{
> +	u8 dspsigsel = chan->type == IIO_MAGN ? 0 : 1;
> +	int ret;
> +
> +	scoped_guard(mutex, &data->fetch_lock) {

As below. guard(mutex) better here to reduce indent a little and indicate the lock
is held for whole function.

> +		ret = regmap_update_bits(data->regmap, SI7210_REG_DSPSIGSEL,
> +					 SI7210_MASK_DSPSIGSEL, dspsigsel);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = regmap_update_bits(data->regmap, SI7210_REG_POWER_CTRL,
> +					 SI7210_MASK_ONEBURST | SI7210_MASK_STOP,
> +					 SI7210_MASK_ONEBURST & ~SI7210_MASK_STOP);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* Read the contents of the registers containing the result: DSPSIGM, DSPSIGL */
> +		ret = regmap_bulk_read(data->regmap, SI7210_REG_DSPSIGM, buf, 2);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int si7210_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	struct si7210_data *data = iio_priv(indio_dev);
> +	long long tmp;
> +	u8 dspsig[2];
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = si7210_fetch_measurement(data, chan, dspsig);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = ((dspsig[0] & 0x7F) << 8) + dspsig[1];

Very nearly a simple endian get. Probably better to treat it like
one anyway. *val = get_unaligned_be16(dpsig) & GENMASK(14, 0)

> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 0;
> +		if (data->curr_scale == 20)
> +			*val2 = 1250;
> +		else /* data->curr_scale == 200 */
> +			*val2 = 12500;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = -16384;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_PROCESSED:
> +		ret = si7210_fetch_measurement(data, chan, dspsig);
> +		if (ret < 0)
> +			return ret;
> +
> +		tmp = ((dspsig[0] & 0x7F) << 5) + (dspsig[1] >> 3);

This may be appropriate as an endian read and FIELD_GET().  Perhaps not worth it
except that the type for the fetch_measurements could then be a __be16 rather than
what looks like unrelated u8 pair.

Given the docs have this a most and least significant bytes that seems to make
sense to me.

> +		tmp = (div_s64(-383 * tmp * tmp, 100) + (160940 * tmp - 279800000));
> +		tmp = (1 + (data->temp_gain >> 11)) * tmp + 62500 * data->temp_offset;
> +		tmp -= 732600;
This is form 0.222 * VDD, given you should have a regulator as per the binding feedback
you should be able to query that voltage.
> +
> +		*val = div_s64_rem(tmp, 1000000, val2);
> +
I think this is returning a value in degrees celsius?  IIO ABI matches older hwmon
on temperatures and is in milicelsius. (Documentation/ABI/testing/sysfs-bus-iio)

Please check other units match the aABI.

> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int si7210_set_scale(struct si7210_data *data, unsigned int scale)
> +{
> +	s8 *a_otp_values;
> +	int ret;
> +
> +	if (scale == 20)
> +		a_otp_values = data->scale_20_a;
> +	else if (scale == 200)
> +		a_otp_values = data->scale_200_a;
> +	else
> +		return -EINVAL;
> +
> +	scoped_guard(mutex, &data->fetch_lock) {
As below (though this one is a little less clear as it's mid way through the function).
I would just used guard()

> +		/* Write the registers 0xCA - 0xCC*/
> +		ret = regmap_bulk_write(data->regmap, SI7210_REG_A0, a_otp_values, 3);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* Write the registers 0xCE - 0xD0*/
> +		ret = regmap_bulk_write(data->regmap, SI7210_REG_A3, &a_otp_values[3], 3);
> +		if (ret < 0)
> +			return ret;
> +
> +		data->curr_scale = scale;
> +	}
> +
> +	return 0;
> +}

> +static int si7210_read_otpreg_val(struct si7210_data *data, unsigned int otpreg, u8 *val)
> +{
> +	int ret;
> +	unsigned int otpdata;
> +
> +	scoped_guard(mutex, &data->otp_lock) {

As you hold the lock for the whole body, I would just use
	guard(mutex)(&datap->otp_lock);
as then the indent of the rest will be reduced, slightly improving readability.

> +		ret = regmap_write(data->regmap, SI7210_REG_OTP_ADDR, otpreg);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = regmap_update_bits(data->regmap, SI7210_REG_OTP_CTRL,
> +					 SI7210_MASK_OTP_READ_EN, SI7210_MASK_OTP_READ_EN);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = regmap_read(data->regmap, SI7210_REG_OTP_DATA, &otpdata);
> +		if (ret < 0)
> +			return ret;
> +
> +		*val = (u8)otpdata;
> +	}
> +
> +	return 0;
> +}
> +
> +static int si7210_device_wake(struct si7210_data *data)
> +{
> +	/* According to the datasheet, the primary method to wake up a device is
> +	 *  to send an empty write. However this is not feasible using current API so we
> +	 *  use the other method i.e. read a single byte. The device should respond with 0xFF
> +	 */
Comment syntax for IIO would make this
	/*
	 * According to the datasheet, the primary method to wake up a
	 * device is to send an empty write. However this is not feasible
	 * using current API so we use the other method i.e. read a single
	 * byte. The device should respond with 0xFF
	 */

> +
> +	int ret = 0;
> +
> +	ret = i2c_smbus_read_byte(data->client);
> +	if (ret < 0)
> +		return ret;
> +
> +	if ((u8)ret != 0xFF)

Why is the cast needed?

> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int si7210_device_init(struct si7210_data *data)
> +{
> +	int ret;
> +	unsigned int i;
> +
> +	ret = si7210_device_wake(data);
> +	if (ret < 0)
> +		return ret;
> +
> +	usleep_range(1000, 1500);

fsleep() preferred.  It'll use slightly different range, but the aim of that
function is we never need to care what exactly is set and consider if the margin
is reasonable or not.

> +
> +	ret = si7210_read_otpreg_val(data, SI7210_OTPREG_TMP_GAIN, &data->temp_gain);
> +	if (ret < 0)
> +		return ret;
> +	ret = si7210_read_otpreg_val(data, SI7210_OTPREG_TMP_OFF, &data->temp_offset);
> +	if (ret < 0)
> +		return ret;
> +
> +	for (i = 0; i < A_REGS_COUNT; i++) {
> +		ret = si7210_read_otpreg_val(data, a20_otp_regs[i], &data->scale_20_a[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	for (i = 0; i < A_REGS_COUNT; i++) {
> +		ret = si7210_read_otpreg_val(data, a200_otp_regs[i], &data->scale_200_a[i]);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	ret = regmap_update_bits(data->regmap, SI7210_REG_ARAUTOINC,
> +				 SI7210_MASK_ARAUTOINC, SI7210_MASK_ARAUTOINC);
> +	if (ret < 0)
> +		return ret;
> +
> +	return si7210_set_scale(data, 20);
> +}
> +
> +static const struct iio_info si7210_info = {
> +	.read_raw = si7210_read_raw,
> +	.write_raw = si7210_write_raw,
> +};
> +
> +static int si7210_probe(struct i2c_client *client)
> +{
> +	struct si7210_data *data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);

Is this used?  If not don't set it.

> +	data->client = client;
> +
> +	mutex_init(&data->fetch_lock);
> +	mutex_init(&data->otp_lock);
> +
> +	data->regmap = devm_regmap_init_i2c(client, &si7210_regmap_conf);
> +	if (IS_ERR(data->regmap))
> +		return dev_err_probe(&client->dev, PTR_ERR(data->regmap),
> +				     "failed to register regmap\n");
> +
> +	indio_dev->name = dev_name(&client->dev);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &si7210_info;
> +	indio_dev->channels = si7210_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(si7210_channels);
> +
> +	ret = si7210_device_init(data);
> +	if (ret)
> +		return dev_err_probe(&client->dev, ret, "device initialization failed\n");

Generally we try to keep the line length in IIO to traditional 80 chars
unless there is a good readability reason to do otherwise.  Here I'd wrap before
the message.

> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id si7210_id[] = {
> +	{ "si7210", 0 },

Trivial: No real point in setting the 0 explicitly.

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, si7210_id);
> +
> +static const struct of_device_id si7210_dt_ids[] = {
> +	{ .compatible = "silabs,si7210" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, si7210_dt_ids);
> +
> +static struct i2c_driver si7210_driver = {
> +	.driver = {
> +		.name = "si7210",
> +		.of_match_table = si7210_dt_ids,
> +	},
> +	.probe		= si7210_probe,
> +	.id_table	= si7210_id,

Totally trivial but I'd not bother with tab alignment at all rather than mixing
using it and not here.
	.probe = si7120_probe, etc is fine and avoids mess of realigning in future
if something longer named turns up.

> +};
> +
> +module_i2c_driver(si7210_driver);
> +MODULE_AUTHOR("Antoni Pokusinski <apokusinski01@gmail.com>");
> +MODULE_DESCRIPTION("Silicon Labs Si7210 Hall Effect sensor I2C driver");
> +MODULE_LICENSE("Dual BSD/GPL");