hwmon: Add MCP3021 ADC driver

Add I2C driver for MCP3021 that is an ADC chip from Microchip.
The MCP3021 is a successive approximation A/D converter (ADC)
with 10-bit resolution.
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@freescale.com>
Signed-off-by: Xie Xiaobo <X.Xie@freescale.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

4 files changed, 204 insertions, 0 deletions

diff --git a/Documentation/hwmon/mcp3021 b/Documentation/hwmon/mcp3021
new file mode 100644
index 000000000000..325fd87e81b2
--- /dev/null
+++ b/Documentation/hwmon/mcp3021
@@ -0,0 +1,22 @@
+Kernel driver MCP3021
+======================
+
+Supported chips:
+  * Microchip Technology MCP3021
+    Prefix: 'mcp3021'
+    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.
+Communication to the MCP3021 is performed using a 2-wire I2C compatible
+interface. Standard (100 kHz) and Fast (400 kHz) I2C modes are available.
+The default I2C device address is 0x4d (contact the Microchip factory for
+additional address options).
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 7190a3f4a827..5b32d56dbb4d 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -813,6 +813,16 @@ config SENSORS_MAX6650
           This driver can also be built as a module.  If so, the module
           will be called max6650.
 
+config SENSORS_MCP3021
+        tristate "Microchip MCP3021"
+        depends on I2C && EXPERIMENTAL
+        help
+          If you say yes here you get support for the MCP3021 chip
+          that is a A/D converter (ADC) with 10-bit resolution.
+
+          This driver can also be built as a module.  If so, the module
+          will be called mcp3021.
+
 config SENSORS_NTC_THERMISTOR
         tristate "NTC thermistor support"
         depends on EXPERIMENTAL
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 8251ce8cd035..6d3f11f71815 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -95,6 +95,7 @@ obj-$(CONFIG_SENSORS_MAX6639)	+= max6639.o
 obj-$(CONFIG_SENSORS_MAX6642)   += max6642.o
 obj-$(CONFIG_SENSORS_MAX6650)   += max6650.o
 obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
+obj-$(CONFIG_SENSORS_MCP3021)   += mcp3021.o
 obj-$(CONFIG_SENSORS_NTC_THERMISTOR)    += ntc_thermistor.o
 obj-$(CONFIG_SENSORS_PC87360)   += pc87360.o
 obj-$(CONFIG_SENSORS_PC87427)   += pc87427.o
diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c
new file mode 100644
index 000000000000..d0afc0cd3ff4
--- /dev/null
+++ b/drivers/hwmon/mcp3021.c
@@ -0,0 +1,171 @@
+/*
+ * mcp3021.c - driver for the Microchip MCP3021 chip
+ *
+ * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
+ * Author: Mingkai Hu <Mingkai.hu@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/hwmon.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/device.h>
+
+/* 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
+
+/*
+ * Client data (each client gets its own)
+ */
+struct mcp3021_data {
+        struct device *hwmon_dev;
+        u32 vdd;        /* device power supply */
+};
+
+static int mcp3021_read16(struct i2c_client *client)
+{
+        int ret;
+        u16 reg;
+        __be16 buf;
+
+        ret = i2c_master_recv(client, (char *)&buf, 2);
+        if (ret < 0)
+                return ret;
+        if (ret != 2)
+                return -EIO;
+
+        /* The output code of the MCP3021 is transmitted with MSB first. */
+        reg = be16_to_cpu(buf);
+
+        /*
+         * 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;
+
+        return reg;
+}
+
+static inline u16 volts_from_reg(u16 vdd, u16 val)
+{
+        if (val == 0)
+                return 0;
+
+        val = val * MCP3021_OUTPUT_SCALE - MCP3021_OUTPUT_SCALE / 2;
+
+        return val * DIV_ROUND_CLOSEST(vdd,
+                        (1 << MCP3021_OUTPUT_RES) * MCP3021_OUTPUT_SCALE);
+}
+
+static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
+                char *buf)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        struct mcp3021_data *data = i2c_get_clientdata(client);
+        int reg, in_input;
+
+        reg = mcp3021_read16(client);
+        if (reg < 0)
+                return reg;
+
+        in_input = volts_from_reg(data->vdd, reg);
+        return sprintf(buf, "%d\n", in_input);
+}
+
+static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);
+
+static int mcp3021_probe(struct i2c_client *client,
+                                const struct i2c_device_id *id)
+{
+        int err;
+        struct mcp3021_data *data = NULL;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+                return -ENODEV;
+
+        data = kzalloc(sizeof(struct mcp3021_data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        i2c_set_clientdata(client, data);
+
+        if (client->dev.platform_data) {
+                data->vdd = *(u32 *)client->dev.platform_data;
+                if (data->vdd > MCP3021_VDD_MAX ||
+                                data->vdd < MCP3021_VDD_MIN) {
+                        err = -EINVAL;
+                        goto exit_free;
+                }
+        } else
+                data->vdd = MCP3021_VDD_REF;
+
+        err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
+        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_file(&client->dev.kobj, &dev_attr_in0_input.attr);
+exit_free:
+        kfree(data);
+        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_file(&client->dev.kobj, &dev_attr_in0_input.attr);
+        kfree(data);
+
+        return 0;
+}
+
+static const struct i2c_device_id mcp3021_id[] = {
+        { "mcp3021", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, mcp3021_id);
+
+static struct i2c_driver mcp3021_driver = {
+        .driver = {
+                .name = "mcp3021",
+        },
+        .probe = mcp3021_probe,
+        .remove = mcp3021_remove,
+        .id_table = mcp3021_id,
+};
+
+module_i2c_driver(mcp3021_driver);
+
+MODULE_AUTHOR("Mingkai Hu <Mingkai.hu@freescale.com>");
+MODULE_DESCRIPTION("Microchip MCP3021 driver");
+MODULE_LICENSE("GPL");