[lm-sensors] [PATCH] hwmon: Add MCP3021 hardware monitoring driver

Xie Xiaobo X.Xie at freescale.com
Tue Dec 27 10:51:02 CET 2011


Add I2C driver for MCP3021 that is an ADC chip from Microchip.
On the MPC8536DS board, there are two MCP3021 chips to monitor the
core and platform current individually. The current is converted
to voltage through a current shunt monitor(INA196) and the voltage
then connected to MCP3021's analog input through a voltage-divider
network. On the board, the relationship between the core/platform
current and the MCP3021's input voltage is as follows:
Icore = 6.0 * Vin
Iplat = 5.5 * Vin
The driver export the value of Vin to sysfs, the voltage unit is
mV. Through the sysfs interface, lm-sensors tool can also display
Vin voltage.

Signed-off-by: Mingkai Hu <Mingkai.hu at freescale.com>
Signed-off-by: Xie Xiaobo <X.Xie at freescale.com>
---
 Documentation/hwmon/mcp3021 |   20 ++++
 drivers/hwmon/Kconfig       |   12 +++
 drivers/hwmon/Makefile      |    1 +
 drivers/hwmon/mcp3021.c     |  223 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 256 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/hwmon/mcp3021
 create mode 100644 drivers/hwmon/mcp3021.c

diff --git a/Documentation/hwmon/mcp3021 b/Documentation/hwmon/mcp3021
new file mode 100644
index 0000000..e5d67d7
--- /dev/null
+++ b/Documentation/hwmon/mcp3021
@@ -0,0 +1,20 @@
+Kernel driver MCP3021
+======================
+
+Supported chips:
+  * Microchip Technology MCP3021
+    Prefix: 'mcp3021'
+    Addresses scanned: I2C 0x4d
+    Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/21805a.pdf
+
+Author: Mingkai Hu
+
+Description
+-----------
+
+This driver implements support for the Microchip Technology MCP3021 chip.
+
+The Microchip Technology Inc. MCP3021 is a successive
+approximation A/D converter (ADC) with 10-bit resolution.
+This device provides one single-ended input with very low
+power consumption.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 91be41f..5af42db 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1360,6 +1360,18 @@ config SENSORS_MC13783_ADC
         help
           Support for the A/D converter on MC13783 PMIC.
 
+config SENSORS_MCP3021
+	tristate "Microchip MCP3021"
+	depends on I2C
+	select HWMON_VID
+	default n
+	help
+	  If you say yes here you get support for the hardware
+	  monitoring functionality of the MCP3021 chip.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called mcp3021.
+
 if ACPI
 
 comment "ACPI drivers"
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 8251ce8..3912557 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ obj-$(CONFIG_SENSORS_W83L785TS)	+= w83l785ts.o
 obj-$(CONFIG_SENSORS_W83L786NG)	+= w83l786ng.o
 obj-$(CONFIG_SENSORS_WM831X)	+= wm831x-hwmon.o
 obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
+obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
 
 obj-$(CONFIG_PMBUS)		+= pmbus/
 
diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c
new file mode 100644
index 0000000..e2ebb8c
--- /dev/null
+++ b/drivers/hwmon/mcp3021.c
@@ -0,0 +1,223 @@
+/*
+ * mcp3021.c - driver for the Microchip MCP3021 chip
+ *
+ * Copyright (C) 2008-2009, 2011 Freescale Semiconductor, Inc.
+ * Author: Mingkai Hu <Mingkai.hu at freescale.com>
+ *
+ * This driver export the value of analog input voltage to sysfs, the
+ * voltage unit is mV. Through the sysfs interface, lm-sensors tool
+ * can also display the input voltage.
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/jiffies.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+
+/*
+ * MCP3021 macros
+ */
+/* Vdd info */
+#define MCP3021_VDD_MAX		5500
+#define MCP3021_VDD_MIN		2700
+#define MCP3021_VDD_REF		3300
+
+/* output format */
+#define MCP3021_SAR_SHIFT	2
+#define MCP3021_SAR_MASK	0x3ff
+
+#define MCP3021_OUTPUT_RES	10	/* 10-bit resolution */
+#define MCP3021_OUTPUT_SCALE	4
+#define MCP3021_OUTPUT_MAX_VAL	((1 << MCP3021_OUTPUT_RES) - 1)
+
+/*
+ * Client data (each client gets its own)
+ */
+struct mcp3021_data {
+	struct device *hwmon_dev;
+	struct mutex update_lock;	/* protect register access */
+
+	/* Register values */
+	u16 in_input;
+};
+
+/*
+ * Driver data (common to all clients)
+ */
+static int mcp3021_probe(struct i2c_client *client,
+				const struct i2c_device_id *id);
+static int mcp3021_remove(struct i2c_client *client);
+
+enum chips { mcp3021 };
+
+static int mcp3021_read16(struct i2c_client *client, u16 *data)
+{
+	int ret;
+	int reg;
+	uint8_t buf[2];
+
+	ret = i2c_master_recv(client, buf, 2);
+	if (ret != 2)
+		return ret;
+
+	/* The output code of the MCP3021 is transmitted with MSB first. */
+	reg = (buf[0] << 8) | buf[1];
+
+	/* The ten-bit output code is composed of the lower 4-bit of the
+	 * first byte and the upper 6-bit of the second byte.
+	 */
+	reg = (reg >> MCP3021_SAR_SHIFT) & MCP3021_SAR_MASK;
+	*data = reg;
+
+	return 0;
+}
+
+/*
+ * The basic transfer function is volts = vdd * val / 1024, except
+ * that at val's limits (0 and 1023), val should have 0.25 added to it.
+ * We scale val by a factor of four so we can add one instead of 0.25.
+ */
+static inline u16 volts_from_reg(u16 vdd, u16 val)
+{
+	val = val * MCP3021_OUTPUT_SCALE;
+
+	if ((val == 0) ||
+	    (val == MCP3021_OUTPUT_MAX_VAL * MCP3021_OUTPUT_SCALE))
+		val++;
+
+	return  val * vdd / ((1 << MCP3021_OUTPUT_RES)
+			* MCP3021_OUTPUT_SCALE);
+}
+
+static struct mcp3021_data *mcp3021_update_device(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct mcp3021_data *data = i2c_get_clientdata(client);
+	u16 vdd = MCP3021_VDD_REF;
+
+	mutex_lock(&data->update_lock);
+	mcp3021_read16(client, &data->in_input);
+	data->in_input = volts_from_reg(vdd, data->in_input);
+	mutex_unlock(&data->update_lock);
+
+	return data;
+}
+
+static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct mcp3021_data *data = mcp3021_update_device(dev);
+	return sprintf(buf, "%d\n", data->in_input);
+}
+
+static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);
+
+static struct attribute *mcp3021_attributes[] = {
+	&dev_attr_in0_input.attr,
+	NULL
+};
+
+static const struct attribute_group mcp3021_group = {
+	.attrs = mcp3021_attributes,
+};
+
+static int mcp3021_check_status(struct i2c_client *client)
+{
+	u16 reg;
+	return  mcp3021_read16(client, &reg);
+}
+
+static int mcp3021_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	int err;
+	struct mcp3021_data *data = NULL;
+
+	if (mcp3021_check_status(client))
+		return -ENXIO;
+	if (!i2c_check_functionality(client->adapter,
+			I2C_FUNC_SMBUS_WORD_DATA))
+		return -EIO;
+
+	data = kzalloc(sizeof(struct mcp3021_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+
+	mutex_init(&data->update_lock);
+
+	err = sysfs_create_group(&client->dev.kobj, &mcp3021_group);
+	if (err)
+		goto exit_free;
+
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		err = PTR_ERR(data->hwmon_dev);
+		goto exit_remove;
+	}
+
+	return 0;
+
+exit_remove:
+	sysfs_remove_group(&client->dev.kobj, &mcp3021_group);
+exit_free:
+	kfree(data);
+	i2c_set_clientdata(client, NULL);
+	return err;
+}
+
+static int mcp3021_remove(struct i2c_client *client)
+{
+	struct mcp3021_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &mcp3021_group);
+	kfree(data);
+	i2c_set_clientdata(client, NULL);
+
+	return 0;
+}
+
+static const struct i2c_device_id mcp3021_id[] = {
+	{ "mcp3021", mcp3021 },
+	{ }
+};
+
+static struct i2c_driver mcp3021_driver = {
+	.driver = {
+		.name = "mcp3021",
+	},
+	.probe = mcp3021_probe,
+	.remove = mcp3021_remove,
+	.id_table = mcp3021_id,
+};
+
+static int __init mcp3021_init(void)
+{
+	return i2c_add_driver(&mcp3021_driver);
+}
+
+static void __exit mcp3021_exit(void)
+{
+	i2c_del_driver(&mcp3021_driver);
+}
+
+MODULE_AUTHOR("Mingkai Hu <Mingkai.hu at freescale.com>");
+MODULE_DESCRIPTION("Microchip MCP3021 driver");
+MODULE_LICENSE("GPL");
+
+module_init(mcp3021_init);
+module_exit(mcp3021_exit);
-- 
1.7.5.1






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