Date:   Thu, 27 Apr 2017 00:03:21 +0930
From:   Joel Stanley <joel@....id.au>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-iio@...r.kernel.org, openbmc@...ts.ozlabs.org,
        Jonathan Cameron <jic23@...nel.org>
Subject: [RFC PATCH] hwmon: Add driver for Infineon DPS310

Hi Guenter,

Below is a work in progress hwmon driver for the DPS310[1]. The device does
both pressure and temperature monitoring over either I2C or SPI. There's a
public datasheet available on Infineon's website.

I require a driver that reads the temperature data over I2C and exposes it to
userspace as a hwmon device. I wanted your opinion weather this should be an
IIO driver (and we could then use the IIO HWMON bridge in our application), or
if it should be a native HWMON driver?

Once we've agreed on a subsystem I will clean the driver up and submit it
properly.

Cheers,

Joel

[1] https://www.infineon.com/cms/en/product/sensor/capacitive-pressure-sensor-for-consumer-applications/channel.html

---

The DPS310 is a temperature and pressure sensor. It can be accessed over
i2c and SPI.

This driver supports continual measurement of temperature over i2c only.

Signed-off-by: Joel Stanley <joel@....id.au>
---
 drivers/hwmon/Kconfig  |  12 ++
 drivers/hwmon/Makefile |   1 +
 drivers/hwmon/dps310.c | 331 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 344 insertions(+)
 create mode 100644 drivers/hwmon/dps310.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 190d270b20a2..8229b2f8c591 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1349,6 +1349,18 @@ config SENSORS_DME1737
 	  This driver can also be built as a module.  If so, the module
 	  will be called dme1737.
 
+config SENSORS_DPS310
+	tristate "Infineon DPS310"
+	depends on I2C
+	select HWMON_VID
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for the hardware monitoring
+	  features of the Infineon DPS310 digital barometric pressure sensor.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called dps310.
+
 config SENSORS_EMC1403
 	tristate "SMSC EMC1403/23 thermal sensor"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index d2cb7e804a0f..3a5ad06d6d89 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
 obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o
 obj-$(CONFIG_SENSORS_DME1737)	+= dme1737.o
+obj-$(CONFIG_SENSORS_DPS310)	+= dps310.o
 obj-$(CONFIG_SENSORS_DS620)	+= ds620.o
 obj-$(CONFIG_SENSORS_DS1621)	+= ds1621.o
 obj-$(CONFIG_SENSORS_EMC1403)	+= emc1403.o
diff --git a/drivers/hwmon/dps310.c b/drivers/hwmon/dps310.c
new file mode 100644
index 000000000000..b014f01d0d3f
--- /dev/null
+++ b/drivers/hwmon/dps310.c
@@ -0,0 +1,331 @@
+/*
+ * Copyright 2017 IBM Corporation
+ *
+ * Joel Stanley <joel@....id.au>
+ *
+ * The DPS310 is a barometric pressure and temperature sensor.
+ *
+ * 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.
+ */
+
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/hwmon.h>
+#include <linux/module.h>
+
+#define PRS_B2		0x00
+#define PRS_B1		0x01
+#define PRS_B0		0x02
+#define TMP_B2		0x03
+#define TMP_B1		0x04
+#define TMP_B0		0x05
+#define PRS_CFG		0x06
+#define TMP_CFG		0x07
+#define  TMP_RATE_BITS	GENMASK(6, 4)
+#define  TMP_EXT	BIT(7)
+#define MEAS_CFG	0x08
+#define  MEAS_CTRL_BITS	GENMASK(2, 0)
+#define   PRESSURE_EN	BIT(0)
+#define   TEMP_EN	BIT(1)
+#define   BACKGROUND	BIT(2)
+#define  PRS_RDY	BIT(4)
+#define  TMP_RDY	BIT(5)
+#define  SENSOR_RDY	BIT(6)
+#define  COEF_RDY	BIT(7)
+#define RESET		0x0c
+#define  RESET_MAGIC	(BIT(0) | BIT(3))
+#define COEF_BASE	0x10
+
+#define TMP_BASE	TMP_B2
+#define PRS_BASE	PRS_B2
+
+#define TMP_RATE(_n)	ilog2(_n)
+#define TMP_PRC(_n)	ilog2(_n)
+
+const int scale_factor[] = {
+	 524288,
+	1572864,
+	3670016,
+	7864320,
+	 253952,
+	 516096,
+	1040384,
+	2088960,
+};
+
+struct dps310_data {
+	struct regmap *regmap;
+	int interval;
+	s32 c0, c1;
+};
+
+static s32 dps310_twos_compliment(u32 raw, size_t num_bits)
+{
+	s32 out = raw;
+
+	if (raw & BIT(num_bits - 1))
+		out = raw - BIT(num_bits);
+
+	return out;
+}
+
+static int dps310_get_temp_coef(struct dps310_data *data)
+{
+	struct regmap *regmap = data->regmap;
+	uint8_t coef[3] = {0};
+	int ready, r;
+	u32 c0, c1;
+
+	r = regmap_read(regmap, MEAS_CFG, &ready);
+	if (r < 0)
+		return r;
+
+	if (!(ready & COEF_RDY))
+		return -EAGAIN;
+
+	/*
+	 * Read temperature calibration coefficients c0 and c1 from the
+	 * COEF register. The numbers are 12-bit 2's compliment numbers
+	 */
+	r = regmap_bulk_read(regmap, COEF_BASE, coef, 3);
+	if (r < 0)
+		return r;
+
+	c0 = (coef[0] << 4) | (coef[1] >> 4);
+	data->c0 = dps310_twos_compliment(c0, 12);
+
+	c1 = ((coef[1] & GENMASK(3, 0)) << 8) | coef[2];
+	data->c1 = dps310_twos_compliment(c1, 12);
+
+	return 0;
+}
+
+static int dps310_get_scale_factor(struct device *dev)
+{
+	struct dps310_data *data = dev_get_drvdata(dev);
+	int val, r;
+
+	r = regmap_read(data->regmap, TMP_CFG, &val);
+	if (r < 0)
+		return r;
+
+	/* Scale factor is bottom 4 bits of the register */
+	val = val & GENMASK(3, 0);
+	if (val < 0 || val > ARRAY_SIZE(scale_factor))
+		return -EINVAL;
+
+	return scale_factor[val];
+}
+
+static int dps310_read_temp(struct device *dev, u32 attr, int channel,
+			     long *temp)
+{
+	struct dps310_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+	uint8_t val[3] = {0};
+	int r, ready;
+	int kT, T_raw;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		r = regmap_read(regmap, MEAS_CFG, &ready);
+		if (r < 0)
+			return r;
+		if (!(ready & TMP_RDY)) {
+			dev_err(dev, "tmp not ready\n");
+			return -EAGAIN;
+		}
+
+		/* Choose scaling factor kT based on chosen precision rate */
+		kT = dps310_get_scale_factor(dev);
+
+		r = regmap_bulk_read(regmap, TMP_BASE, val, 3);
+		if (r < 0)
+			return r;
+		T_raw = (val[0] << 16) | (val[1] << 8) | val[2];
+		T_raw = dps310_twos_compliment(T_raw, 24);
+
+		/* (c0 * 0.5 + c1 * T_raw / kT) * 1000 m°C */
+		*temp = ((data->c0 >> 1) + (data->c1 * T_raw) / kT) * 1000;
+
+		return 0;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int dps310_read(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long *val)
+{
+	switch (type) {
+	case hwmon_temp:
+		return dps310_read_temp(dev, attr, channel, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int dps310_write(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long val)
+{
+	switch (type) {
+	case hwmon_temp:
+		/* Fall through */
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static umode_t dps310_is_visible(const void *data,
+				  enum hwmon_sensor_types type,
+				  u32 attr, int channel)
+{
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return 0444;
+		default:
+			return 0;
+		}
+	default:
+		return 0;
+	}
+}
+
+
+static const u32 dps310_temp_config[] = {
+	HWMON_T_INPUT,
+	0
+};
+
+static const struct hwmon_channel_info dps310_temp = {
+	.type = hwmon_temp,
+	.config = dps310_temp_config,
+};
+
+static const struct hwmon_channel_info *dps310_info[] = {
+	&dps310_temp,
+	NULL
+};
+
+static const struct hwmon_ops dps310_hwmon_ops = {
+	.is_visible = dps310_is_visible,
+	.read = dps310_read,
+	.write = dps310_write,
+};
+
+static const struct hwmon_chip_info dps310_chip_info = {
+	.ops = &dps310_hwmon_ops,
+	.info = dps310_info,
+};
+
+static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case PRS_CFG:
+	case TMP_CFG:
+	case MEAS_CFG:
+	case RESET:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case PRS_B2:
+	case PRS_B1:
+	case PRS_B0:
+	case TMP_B2:
+	case TMP_B1:
+	case TMP_B0:
+	case MEAS_CFG:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config dps310_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.writeable_reg = dps310_is_writeable_reg,
+	.volatile_reg = dps310_is_volatile_reg,
+	.cache_type = REGCACHE_RBTREE,
+	.use_single_rw = true,
+};
+
+static int dps310_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct dps310_data *data;
+	struct device *hwmon_dev;
+	int r;
+
+	data = devm_kzalloc(&client->dev,  sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->regmap = devm_regmap_init_i2c(client, &dps310_regmap_config);
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
+
+	r = regmap_write(data->regmap, TMP_CFG, TMP_EXT | TMP_PRC(128));
+	if (r < 0)
+		return r;
+
+	/* Turn on background temperature measurement */
+	r = regmap_update_bits(data->regmap, MEAS_CFG, MEAS_CTRL_BITS,
+			TEMP_EN);
+	if (r < 0)
+		return r;
+
+	/* Get calibration coefficients required for reporting temperature */
+	r = dps310_get_temp_coef(data);
+	if (r == -EAGAIN)
+		return -EPROBE_DEFER;
+	if (r < 0)
+		return r;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
+			client->name, data, &dps310_chip_info, NULL);
+
+	if (IS_ERR(hwmon_dev))
+		return PTR_ERR(hwmon_dev);
+
+	dev_info(&client->dev, "%s: sensor '%s'\n", dev_name(hwmon_dev),
+			client->name);
+
+	return 0;
+}
+
+static const struct i2c_device_id dps310_id[] = {
+	{ "dps310", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, dps310_id);
+
+static const unsigned short normal_i2c[] = {
+	0x77, 0x76, I2C_CLIENT_END
+};
+
+static struct i2c_driver dps310_driver = {
+	.class = I2C_CLASS_HWMON,
+	.driver = {
+		.name = "dps310",
+	},
+	.probe = dps310_probe,
+	.address_list = normal_i2c,
+	.id_table = dps310_id,
+};
+module_i2c_driver(dps310_driver);
+
+MODULE_AUTHOR("Joel Stanley <joel@....id.au>");
+MODULE_DESCRIPTION("Infineon DPS310 driver");
+MODULE_LICENSE("GPL");
-- 
2.11.0

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