Message-ID: <0b72866f4e5ac28c78f6d683a1ca659a4239b68e.1760374257.git.akhilesh@ee.iitb.ac.in>
Date: Mon, 13 Oct 2025 22:32:35 +0530
From: Akhilesh Patil <akhilesh@...iitb.ac.in>
To: jic23@...nel.org, dlechner@...libre.com, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, nuno.sa@...log.com,
	andy@...nel.org, marcelo.schmitt1@...il.com, vassilisamir@...il.com,
	salah.triki@...il.com
Cc: skhan@...uxfoundation.org, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	akhileshpatilvnit@...il.com
Subject: [PATCH v2 2/2] iio: pressure: adp810: Add driver for adp810 sensor

Add driver for Aosong adp810 differential pressure and temperature sensor.
This sensor provides an I2C interface for reading data.
Calculate CRC of the data received using standard crc8 library to verify
data integrity.

Tested on TI am62x sk board with sensor connected at i2c-2.

Signed-off-by: Akhilesh Patil <akhilesh@...iitb.ac.in>
---
 MAINTAINERS                   |   7 ++
 drivers/iio/pressure/Kconfig  |  12 ++
 drivers/iio/pressure/Makefile |   8 +-
 drivers/iio/pressure/adp810.c | 212 ++++++++++++++++++++++++++++++++++
 4 files changed, 235 insertions(+), 4 deletions(-)
 create mode 100644 drivers/iio/pressure/adp810.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 46126ce2f968..bb30f7b31cb7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3745,6 +3745,13 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/aosong,ags02ma.yaml
 F:	drivers/iio/chemical/ags02ma.c
 
+AOSONG ADP810 DIFFERENTIAL PRESSURE SENSOR DRIVER
+M:	Akhilesh Patil <akhilesh@...iitb.ac.in>
+L:	linux-iio@...r.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/pressure/aosong,adp810.yaml
+F:	drivers/iio/pressure/adp810.c
+
 ASC7621 HARDWARE MONITOR DRIVER
 M:	George Joseph <george.joseph@...rview5.com>
 L:	linux-hwmon@...r.kernel.org
diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index d2cb8c871f6a..2fe9dc90cceb 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -339,4 +339,16 @@ config ZPA2326_SPI
 	tristate
 	select REGMAP_SPI
 
+config ADP810
+	tristate "Aosong adp810 differential pressure and temperature sensor"
+	depends on I2C
+	select CRC8
+	help
+	  Say yes here to build adp810 differential pressure and temperature
+	  sensor driver. ADP810 can measure pressure range up to 500Pa.
+	  It supports an I2C interface for data communication.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called adp810
+
 endmenu
diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
index 6482288e07ee..a21443e992b9 100644
--- a/drivers/iio/pressure/Makefile
+++ b/drivers/iio/pressure/Makefile
@@ -5,6 +5,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_ABP060MG) += abp060mg.o
+obj-$(CONFIG_ADP810) += adp810.o
 obj-$(CONFIG_ROHM_BM1390) += rohm-bm1390.o
 obj-$(CONFIG_BMP280) += bmp280.o
 bmp280-objs := bmp280-core.o bmp280-regmap.o
@@ -15,6 +16,7 @@ obj-$(CONFIG_DPS310) += dps310.o
 obj-$(CONFIG_IIO_CROS_EC_BARO) += cros_ec_baro.o
 obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
 obj-$(CONFIG_HP03) += hp03.o
+obj-$(CONFIG_HP206C) += hp206c.o
 obj-$(CONFIG_HSC030PA) += hsc030pa.o
 obj-$(CONFIG_HSC030PA_I2C) += hsc030pa_i2c.o
 obj-$(CONFIG_HSC030PA_SPI) += hsc030pa_spi.o
@@ -34,11 +36,9 @@ obj-$(CONFIG_SDP500) += sdp500.o
 obj-$(CONFIG_IIO_ST_PRESS) += st_pressure.o
 st_pressure-y := st_pressure_core.o
 st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
+obj-$(CONFIG_IIO_ST_PRESS_I2C) += st_pressure_i2c.o
+obj-$(CONFIG_IIO_ST_PRESS_SPI) += st_pressure_spi.o
 obj-$(CONFIG_T5403) += t5403.o
-obj-$(CONFIG_HP206C) += hp206c.o
 obj-$(CONFIG_ZPA2326) += zpa2326.o
 obj-$(CONFIG_ZPA2326_I2C) += zpa2326_i2c.o
 obj-$(CONFIG_ZPA2326_SPI) += zpa2326_spi.o
-
-obj-$(CONFIG_IIO_ST_PRESS_I2C) += st_pressure_i2c.o
-obj-$(CONFIG_IIO_ST_PRESS_SPI) += st_pressure_spi.o
diff --git a/drivers/iio/pressure/adp810.c b/drivers/iio/pressure/adp810.c
new file mode 100644
index 000000000000..c2f3b5f7a1f9
--- /dev/null
+++ b/drivers/iio/pressure/adp810.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2025 Akhilesh Patil <akhilesh@...iitb.ac.in>
+ *
+ * Driver for adp810 pressure and temperature sensor
+ * Datasheet:
+ *   https://aosong.com/userfiles/files/media/Datasheet%20ADP810-Digital.pdf
+ */
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/unaligned.h>
+
+#include <linux/iio/iio.h>
+
+/*
+ * Time taken in ms by sensor to do measurements after triggering.
+ * As per datasheet 10ms is sufficient but we define 30ms for better margin.
+ */
+#define ADP810_MEASURE_LATENCY_MS	30
+/* Trigger command to send to start measurement by the sensor */
+#define ADP810_TRIGGER_COMMAND		0x2d37
+/*
+ * Refer section 5.4 checksum calculation from datasheet.
+ * This sensor uses CRC polynomial x^8 + x^5 + x^4 + 1 (0x31)
+ */
+#define ADP810_CRC8_POLYNOMIAL		0x31
+
+DECLARE_CRC8_TABLE(crc_table);
+
+struct adp810_read_buf {
+	__be16 dp;
+	u8 dp_crc;
+	__be16 tmp;
+	u8 tmp_crc;
+	__be16 sf;
+	u8 sf_crc;
+} __packed;
+
+struct adp810_data {
+	struct i2c_client *client;
+	/* Use lock to synchronize access to device during read sequence */
+	struct mutex lock;
+};
+
+static int adp810_measure(struct adp810_data *data, struct adp810_read_buf *buf)
+{
+	struct i2c_client *client = data->client;
+	struct device *dev = &client->dev;
+	int ret;
+	u16 trig_cmd = ADP810_TRIGGER_COMMAND;
+
+	/* Send trigger to the sensor for measurement */
+	ret = i2c_master_send(client, (char *)&trig_cmd, sizeof(u16));
+	if (ret < 0) {
+		dev_err(dev, "Error sending trigger command\n");
+		return ret;
+	}
+
+	/*
+	 * Wait for the sensor to acquire data. As per datasheet section 5.3.1,
+	 * wait for at least 10ms before reading measurements from the sensor.
+	 */
+	msleep(ADP810_MEASURE_LATENCY_MS);
+
+	/* Read sensor values */
+	ret = i2c_master_recv(client, (char *)buf, sizeof(*buf));
+	if (ret < 0) {
+		dev_err(dev, "Error reading from sensor\n");
+		return ret;
+	}
+
+	/* CRC checks */
+	crc8_populate_msb(crc_table, ADP810_CRC8_POLYNOMIAL);
+	if (buf->dp_crc != crc8(crc_table, (u8 *)&buf->dp, 0x2, CRC8_INIT_VALUE)) {
+		dev_err(dev, "CRC error for pressure\n");
+		return -EIO;
+	}
+
+	if (buf->tmp_crc != crc8(crc_table, (u8 *)&buf->tmp, 0x2, CRC8_INIT_VALUE)) {
+		dev_err(dev, "CRC error for temperature\n");
+		return -EIO;
+	}
+
+	if (buf->sf_crc != crc8(crc_table, (u8 *)&buf->sf, 0x2, CRC8_INIT_VALUE)) {
+		dev_err(dev, "CRC error for scale\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int adp810_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct adp810_data *data = iio_priv(indio_dev);
+	struct device *dev = &data->client->dev;
+	struct adp810_read_buf buf = {0};
+	int ret;
+
+	scoped_guard(mutex, &data->lock) {
+		ret = adp810_measure(data, &buf);
+		if (ret) {
+			dev_err(dev, "Failed to read from device\n");
+			return ret;
+		}
+	}
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = get_unaligned_be16(&buf.dp);
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			*val = get_unaligned_be16(&buf.tmp);
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = get_unaligned_be16(&buf.sf);
+			return IIO_VAL_INT;
+		case IIO_TEMP:
+			*val = 200;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info adp810_info = {
+	.read_raw	= adp810_read_raw,
+};
+
+static const struct iio_chan_spec adp810_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static int adp810_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct iio_dev *indio_dev;
+	struct adp810_data *data;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+
+	ret = devm_mutex_init(dev, &data->lock);
+	if (ret)
+		return ret;
+
+	indio_dev->name = "adp810";
+	indio_dev->channels = adp810_channels;
+	indio_dev->num_channels = ARRAY_SIZE(adp810_channels);
+	indio_dev->info = &adp810_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register IIO device\n");
+
+	return 0;
+}
+
+static const struct i2c_device_id adp810_id_table[] = {
+	{ "adp810" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, adp810_id_table);
+
+static const struct of_device_id adp810_of_table[] = {
+	{ .compatible = "aosong,adp810" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, adp810_of_table);
+
+static struct i2c_driver adp810_driver = {
+	.driver = {
+		.name = "adp810",
+		.of_match_table = adp810_of_table,
+	},
+	.probe	= adp810_probe,
+	.id_table = adp810_id_table,
+};
+module_i2c_driver(adp810_driver);
+
+MODULE_AUTHOR("Akhilesh Patil <akhilesh@...iitb.ac.in>");
+MODULE_DESCRIPTION("Driver for Aosong ADP810 sensor");
+MODULE_LICENSE("GPL");
-- 
2.34.1

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