iio: light: add MAX30100 oximeter driver support

MAX30100 is an heart rate and pulse oximeter sensor that works using
two LEDS of different wavelengths, and detecting the light reflected
back.

This patchset adds support for both IR and RED LED channels which can
be processed in userspace to determine heart rate and blood oxygen
levels.
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/health/max30100.txt

+Maxim MAX30100 heart rate and pulse oximeter sensor
+
+* https://datasheets.maximintegrated.com/en/ds/MAX30100.pdf
+
+Required properties:
+  - compatible: must be "maxim,max30100"
+  - reg: the I2C address of the sensor
+  - interrupt-parent: should be the phandle for the interrupt controller
+  - interrupts: the sole interrupt generated by the device
+
+  Refer to interrupt-controller/interrupts.txt for generic
+  interrupt client node bindings.
+
+Example:
+
+max30100@057 {
+	compatible = "maxim,max30100";
+	reg = <57>;
+	interrupt-parent = <&gpio1>;
+	interrupts = <16 2>;
+};

drivers/iio/Kconfig

@@ -69,6 +69,7 @@ source "drivers/iio/dac/Kconfig"
 source "drivers/iio/dummy/Kconfig"
 source "drivers/iio/frequency/Kconfig"
 source "drivers/iio/gyro/Kconfig"
+source "drivers/iio/health/Kconfig"
 source "drivers/iio/humidity/Kconfig"
 source "drivers/iio/imu/Kconfig"
 source "drivers/iio/light/Kconfig"

drivers/iio/Makefile

@@ -21,6 +21,7 @@ obj-y += dac/
 obj-y += dummy/
 obj-y += gyro/
 obj-y += frequency/
+obj-y += health/
 obj-y += humidity/
 obj-y += imu/
 obj-y += light/

drivers/iio/health/Kconfig

+#
+# Health sensors
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Health sensors"
+
+config MAX30100
+	tristate "MAX30100 heart rate and pulse oximeter sensor"
+	depends on I2C
+	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_KFIFO_BUF
+	help
+	  Say Y here to build I2C interface support for the Maxim
+	  MAX30100 heart rate, and pulse oximeter sensor.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called max30100.
+
+endmenu

drivers/iio/health/Makefile

+#
+# Makefile for IIO Health sensors
+#
+
+# When adding new entries keep the list in alphabetical order
+
+obj-$(CONFIG_MAX30100)		+= max30100.o

drivers/iio/health/max30100.c

+/*
+ * max30100.c - Support for MAX30100 heart rate and pulse oximeter sensor
+ *
+ * Copyright (C) 2015 Matt Ranostay <mranostay@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * TODO: allow LED current and pulse length controls via device tree properties
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/irq.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+
+#define MAX30100_REGMAP_NAME	"max30100_regmap"
+#define MAX30100_DRV_NAME	"max30100"
+
+#define MAX30100_REG_INT_STATUS			0x00
+#define MAX30100_REG_INT_STATUS_PWR_RDY		BIT(0)
+#define MAX30100_REG_INT_STATUS_SPO2_RDY	BIT(4)
+#define MAX30100_REG_INT_STATUS_HR_RDY		BIT(5)
+#define MAX30100_REG_INT_STATUS_FIFO_RDY	BIT(7)
+
+#define MAX30100_REG_INT_ENABLE			0x01
+#define MAX30100_REG_INT_ENABLE_SPO2_EN		BIT(0)
+#define MAX30100_REG_INT_ENABLE_HR_EN		BIT(1)
+#define MAX30100_REG_INT_ENABLE_FIFO_EN		BIT(3)
+#define MAX30100_REG_INT_ENABLE_MASK		0xf0
+#define MAX30100_REG_INT_ENABLE_MASK_SHIFT	4
+
+#define MAX30100_REG_FIFO_WR_PTR		0x02
+#define MAX30100_REG_FIFO_OVR_CTR		0x03
+#define MAX30100_REG_FIFO_RD_PTR		0x04
+#define MAX30100_REG_FIFO_DATA			0x05
+#define MAX30100_REG_FIFO_DATA_ENTRY_COUNT	16
+#define MAX30100_REG_FIFO_DATA_ENTRY_LEN	4
+
+#define MAX30100_REG_MODE_CONFIG		0x06
+#define MAX30100_REG_MODE_CONFIG_MODE_SPO2_EN	BIT(0)
+#define MAX30100_REG_MODE_CONFIG_MODE_HR_EN	BIT(1)
+#define MAX30100_REG_MODE_CONFIG_MODE_MASK	0x03
+#define MAX30100_REG_MODE_CONFIG_TEMP_EN	BIT(3)
+#define MAX30100_REG_MODE_CONFIG_PWR		BIT(7)
+
+#define MAX30100_REG_SPO2_CONFIG		0x07
+#define MAX30100_REG_SPO2_CONFIG_100HZ		BIT(2)
+#define MAX30100_REG_SPO2_CONFIG_HI_RES_EN	BIT(6)
+#define MAX30100_REG_SPO2_CONFIG_1600US		0x3
+
+#define MAX30100_REG_LED_CONFIG			0x09
+#define MAX30100_REG_LED_CONFIG_RED_LED_SHIFT	4
+
+#define MAX30100_REG_LED_CONFIG_24MA		0x07
+#define MAX30100_REG_LED_CONFIG_50MA		0x0f
+
+#define MAX30100_REG_TEMP_INTEGER		0x16
+#define MAX30100_REG_TEMP_FRACTION		0x17
+
+struct max30100_data {
+	struct i2c_client *client;
+	struct iio_dev *indio_dev;
+	struct mutex lock;
+	struct regmap *regmap;
+
+	__be16 buffer[2]; /* 2 16-bit channels */
+};
+
+static bool max30100_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MAX30100_REG_INT_STATUS:
+	case MAX30100_REG_MODE_CONFIG:
+	case MAX30100_REG_FIFO_WR_PTR:
+	case MAX30100_REG_FIFO_OVR_CTR:
+	case MAX30100_REG_FIFO_RD_PTR:
+	case MAX30100_REG_FIFO_DATA:
+	case MAX30100_REG_TEMP_INTEGER:
+	case MAX30100_REG_TEMP_FRACTION:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config max30100_regmap_config = {
+	.name = MAX30100_REGMAP_NAME,
+
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = MAX30100_REG_TEMP_FRACTION,
+	.cache_type = REGCACHE_FLAT,
+
+	.volatile_reg = max30100_is_volatile_reg,
+};
+
+static const unsigned long max30100_scan_masks[] = {0x3, 0};
+
+static const struct iio_chan_spec max30100_channels[] = {
+	{
+		.type = IIO_INTENSITY,
+		.channel2 = IIO_MOD_LIGHT_IR,
+		.modified = 1,
+
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 16,
+			.storagebits = 16,
+			.endianness = IIO_BE,
+		},
+	},
+	{
+		.type = IIO_INTENSITY,
+		.channel2 = IIO_MOD_LIGHT_RED,
+		.modified = 1,
+
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 16,
+			.storagebits = 16,
+			.endianness = IIO_BE,
+		},
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = -1,
+	},
+};
+
+static int max30100_set_powermode(struct max30100_data *data, bool state)
+{
+	return regmap_update_bits(data->regmap, MAX30100_REG_MODE_CONFIG,
+				  MAX30100_REG_MODE_CONFIG_PWR,
+				  state ? 0 : MAX30100_REG_MODE_CONFIG_PWR);
+}
+
+static int max30100_clear_fifo(struct max30100_data *data)
+{
+	int ret;
+
+	ret = regmap_write(data->regmap, MAX30100_REG_FIFO_WR_PTR, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(data->regmap, MAX30100_REG_FIFO_OVR_CTR, 0);
+	if (ret)
+		return ret;
+
+	return regmap_write(data->regmap, MAX30100_REG_FIFO_RD_PTR, 0);
+}
+
+static int max30100_buffer_postenable(struct iio_dev *indio_dev)
+{
+	struct max30100_data *data = iio_priv(indio_dev);
+	int ret;
+
+	ret = max30100_set_powermode(data, true);
+	if (ret)
+		return ret;
+
+	return max30100_clear_fifo(data);
+}
+
+static int max30100_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct max30100_data *data = iio_priv(indio_dev);
+
+	return max30100_set_powermode(data, false);
+}
+
+static const struct iio_buffer_setup_ops max30100_buffer_setup_ops = {
+	.postenable = max30100_buffer_postenable,
+	.predisable = max30100_buffer_predisable,
+};
+
+static inline int max30100_fifo_count(struct max30100_data *data)
+{
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(data->regmap, MAX30100_REG_INT_STATUS, &val);
+	if (ret)
+		return ret;
+
+	/* FIFO is almost full */
+	if (val & MAX30100_REG_INT_STATUS_FIFO_RDY)
+		return MAX30100_REG_FIFO_DATA_ENTRY_COUNT - 1;
+
+	return 0;
+}
+
+static int max30100_read_measurement(struct max30100_data *data)
+{
+	int ret;
+
+	ret = i2c_smbus_read_i2c_block_data(data->client,
+					    MAX30100_REG_FIFO_DATA,
+					    MAX30100_REG_FIFO_DATA_ENTRY_LEN,
+					    (u8 *) &data->buffer);
+
+	return (ret == MAX30100_REG_FIFO_DATA_ENTRY_LEN) ? 0 : ret;
+}
+
+static irqreturn_t max30100_interrupt_handler(int irq, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct max30100_data *data = iio_priv(indio_dev);
+	int ret, cnt = 0;
+
+	mutex_lock(&data->lock);
+
+	while (cnt-- || (cnt = max30100_fifo_count(data) > 0)) {
+		ret = max30100_read_measurement(data);
+		if (ret)
+			break;
+
+		iio_push_to_buffers(data->indio_dev, data->buffer);
+	}
+
+	mutex_unlock(&data->lock);
+
+	return IRQ_HANDLED;
+}
+
+static int max30100_chip_init(struct max30100_data *data)
+{
+	int ret;
+
+	/* RED IR LED = 24mA, IR LED = 50mA */
+	ret = regmap_write(data->regmap, MAX30100_REG_LED_CONFIG,
+				(MAX30100_REG_LED_CONFIG_24MA <<
+				 MAX30100_REG_LED_CONFIG_RED_LED_SHIFT) |
+				 MAX30100_REG_LED_CONFIG_50MA);
+	if (ret)
+		return ret;
+
+	/* enable hi-res SPO2 readings at 100Hz */
+	ret = regmap_write(data->regmap, MAX30100_REG_SPO2_CONFIG,
+				 MAX30100_REG_SPO2_CONFIG_HI_RES_EN |
+				 MAX30100_REG_SPO2_CONFIG_100HZ);
+	if (ret)
+		return ret;
+
+	/* enable SPO2 mode */
+	ret = regmap_update_bits(data->regmap, MAX30100_REG_MODE_CONFIG,
+				 MAX30100_REG_MODE_CONFIG_MODE_MASK,
+				 MAX30100_REG_MODE_CONFIG_MODE_HR_EN |
+				 MAX30100_REG_MODE_CONFIG_MODE_SPO2_EN);
+	if (ret)
+		return ret;
+
+	/* enable FIFO interrupt */
+	return regmap_update_bits(data->regmap, MAX30100_REG_INT_ENABLE,
+				 MAX30100_REG_INT_ENABLE_MASK,
+				 MAX30100_REG_INT_ENABLE_FIFO_EN
+				 << MAX30100_REG_INT_ENABLE_MASK_SHIFT);
+}
+
+static int max30100_read_temp(struct max30100_data *data, int *val)
+{
+	int ret;
+	unsigned int reg;
+
+	ret = regmap_read(data->regmap, MAX30100_REG_TEMP_INTEGER, &reg);
+	if (ret < 0)
+		return ret;
+	*val = reg << 4;
+
+	ret = regmap_read(data->regmap, MAX30100_REG_TEMP_FRACTION, &reg);
+	if (ret < 0)
+		return ret;
+
+	*val |= reg & 0xf;
+	*val = sign_extend32(*val, 11);
+
+	return 0;
+}
+
+static int max30100_get_temp(struct max30100_data *data, int *val)
+{
+	int ret;
+
+	/* start acquisition */
+	ret = regmap_update_bits(data->regmap, MAX30100_REG_MODE_CONFIG,
+				 MAX30100_REG_MODE_CONFIG_TEMP_EN,
+				 MAX30100_REG_MODE_CONFIG_TEMP_EN);
+	if (ret)
+		return ret;
+
+	usleep_range(35000, 50000);
+
+	return max30100_read_temp(data, val);
+}
+
+static int max30100_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max30100_data *data = iio_priv(indio_dev);
+	int ret = -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		/*
+		 * Temperature reading can only be acquired while engine
+		 * is running
+		 */
+		mutex_lock(&indio_dev->mlock);
+
+		if (!iio_buffer_enabled(indio_dev))
+			ret = -EAGAIN;
+		else {
+			ret = max30100_get_temp(data, val);
+			if (!ret)
+				ret = IIO_VAL_INT;
+
+		}
+
+		mutex_unlock(&indio_dev->mlock);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1;  /* 0.0625 */
+		*val2 = 16;
+		ret = IIO_VAL_FRACTIONAL;
+		break;
+	}
+
+	return ret;
+}
+
+static const struct iio_info max30100_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = max30100_read_raw,
+};
+
+static int max30100_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct max30100_data *data;
+	struct iio_buffer *buffer;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	buffer = devm_iio_kfifo_allocate(&client->dev);
+	if (!buffer)
+		return -ENOMEM;
+
+	iio_device_attach_buffer(indio_dev, buffer);
+
+	indio_dev->name = MAX30100_DRV_NAME;
+	indio_dev->channels = max30100_channels;
+	indio_dev->info = &max30100_info;
+	indio_dev->num_channels = ARRAY_SIZE(max30100_channels);
+	indio_dev->available_scan_masks = max30100_scan_masks;
+	indio_dev->modes = (INDIO_BUFFER_SOFTWARE | INDIO_DIRECT_MODE);
+	indio_dev->setup_ops = &max30100_buffer_setup_ops;
+
+	data = iio_priv(indio_dev);
+	data->indio_dev = indio_dev;
+	data->client = client;
+
+	mutex_init(&data->lock);
+	i2c_set_clientdata(client, indio_dev);
+
+	data->regmap = devm_regmap_init_i2c(client, &max30100_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(&client->dev, "regmap initialization failed.\n");
+		return PTR_ERR(data->regmap);
+	}
+	max30100_set_powermode(data, false);
+
+	ret = max30100_chip_init(data);
+	if (ret)
+		return ret;
+
+	if (client->irq <= 0) {
+		dev_err(&client->dev, "no valid irq defined\n");
+		return -EINVAL;
+	}
+	ret = devm_request_threaded_irq(&client->dev, client->irq,
+					NULL, max30100_interrupt_handler,
+					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+					"max30100_irq", indio_dev);
+	if (ret) {
+		dev_err(&client->dev, "request irq (%d) failed\n", client->irq);
+		return ret;
+	}
+
+	return iio_device_register(indio_dev);
+}
+
+static int max30100_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct max30100_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	max30100_set_powermode(data, false);
+
+	return 0;
+}
+
+static const struct i2c_device_id max30100_id[] = {
+	{ "max30100", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, max30100_id);
+
+static const struct of_device_id max30100_dt_ids[] = {
+	{ .compatible = "maxim,max30100" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max30100_dt_ids);
+
+static struct i2c_driver max30100_driver = {
+	.driver = {
+		.name	= MAX30100_DRV_NAME,
+		.of_match_table	= of_match_ptr(max30100_dt_ids),
+	},
+	.probe		= max30100_probe,
+	.remove		= max30100_remove,
+	.id_table	= max30100_id,
+};
+module_i2c_driver(max30100_driver);
+
+MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
+MODULE_DESCRIPTION("MAX30100 heart rate and pulse oximeter sensor");
+MODULE_LICENSE("GPL");