1/*
  2 * mcp3021.c - driver for the Microchip MCP3021 chip
  3 *
  4 * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
  5 * Author: Mingkai Hu <Mingkai.hu@freescale.com>
  6 *
  7 * This driver export the value of analog input voltage to sysfs, the
  8 * voltage unit is mV. Through the sysfs interface, lm-sensors tool
  9 * can also display the input voltage.
 10 *
 11 * This program is free software; you can redistribute it and/or modify
 12 * it under the terms of the GNU General Public License as published by
 13 * the Free Software Foundation; either version 2 of the License, or
 14 * (at your option) any later version.
 15 */
 16
 17#include <linux/kernel.h>
 18#include <linux/module.h>
 19#include <linux/hwmon.h>
 20#include <linux/slab.h>
 21#include <linux/i2c.h>
 22#include <linux/err.h>
 23#include <linux/device.h>
 24
 25/* Vdd info */
 26#define MCP3021_VDD_MAX		5500
 27#define MCP3021_VDD_MIN		2700
 28#define MCP3021_VDD_REF		3300
 29
 30/* output format */
 31#define MCP3021_SAR_SHIFT	2
 32#define MCP3021_SAR_MASK	0x3ff
 33
 34#define MCP3021_OUTPUT_RES	10	/* 10-bit resolution */
 35#define MCP3021_OUTPUT_SCALE	4
 36
 37/*
 38 * Client data (each client gets its own)
 39 */
 40struct mcp3021_data {
 41	struct device *hwmon_dev;
 42	u32 vdd;	/* device power supply */
 43};
 44
 45static int mcp3021_read16(struct i2c_client *client)
 46{
 47	int ret;
 48	u16 reg;
 49	__be16 buf;
 50
 51	ret = i2c_master_recv(client, (char *)&buf, 2);
 52	if (ret < 0)
 53		return ret;
 54	if (ret != 2)
 55		return -EIO;
 56
 57	/* The output code of the MCP3021 is transmitted with MSB first. */
 58	reg = be16_to_cpu(buf);
 59
 60	/*
 61	 * The ten-bit output code is composed of the lower 4-bit of the
 62	 * first byte and the upper 6-bit of the second byte.
 63	 */
 64	reg = (reg >> MCP3021_SAR_SHIFT) & MCP3021_SAR_MASK;
 65
 66	return reg;
 67}
 68
 69static inline u16 volts_from_reg(u16 vdd, u16 val)
 70{
 71	if (val == 0)
 72		return 0;
 73
 74	val = val * MCP3021_OUTPUT_SCALE - MCP3021_OUTPUT_SCALE / 2;
 75
 76	return val * DIV_ROUND_CLOSEST(vdd,
 77			(1 << MCP3021_OUTPUT_RES) * MCP3021_OUTPUT_SCALE);
 78}
 79
 80static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
 81		char *buf)
 82{
 83	struct i2c_client *client = to_i2c_client(dev);
 84	struct mcp3021_data *data = i2c_get_clientdata(client);
 85	int reg, in_input;
 86
 87	reg = mcp3021_read16(client);
 88	if (reg < 0)
 89		return reg;
 90
 91	in_input = volts_from_reg(data->vdd, reg);
 92	return sprintf(buf, "%d\n", in_input);
 93}
 94
 95static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);
 96
 97static int mcp3021_probe(struct i2c_client *client,
 98				const struct i2c_device_id *id)
 99{
100	int err;
101	struct mcp3021_data *data = NULL;
102
103	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
104		return -ENODEV;
105
106	data = kzalloc(sizeof(struct mcp3021_data), GFP_KERNEL);
107	if (!data)
108		return -ENOMEM;
109
110	i2c_set_clientdata(client, data);
111
112	if (client->dev.platform_data) {
113		data->vdd = *(u32 *)client->dev.platform_data;
114		if (data->vdd > MCP3021_VDD_MAX ||
115				data->vdd < MCP3021_VDD_MIN) {
116			err = -EINVAL;
117			goto exit_free;
118		}
119	} else
120		data->vdd = MCP3021_VDD_REF;
121
122	err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
123	if (err)
124		goto exit_free;
125
126	data->hwmon_dev = hwmon_device_register(&client->dev);
127	if (IS_ERR(data->hwmon_dev)) {
128		err = PTR_ERR(data->hwmon_dev);
129		goto exit_remove;
130	}
131
132	return 0;
133
134exit_remove:
135	sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr);
136exit_free:
137	kfree(data);
138	return err;
139}
140
141static int mcp3021_remove(struct i2c_client *client)
142{
143	struct mcp3021_data *data = i2c_get_clientdata(client);
144
145	hwmon_device_unregister(data->hwmon_dev);
146	sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr);
147	kfree(data);
148
149	return 0;
150}
151
152static const struct i2c_device_id mcp3021_id[] = {
153	{ "mcp3021", 0 },
154	{ }
155};
156MODULE_DEVICE_TABLE(i2c, mcp3021_id);
157
158static struct i2c_driver mcp3021_driver = {
159	.driver = {
160		.name = "mcp3021",
161	},
162	.probe = mcp3021_probe,
163	.remove = mcp3021_remove,
164	.id_table = mcp3021_id,
165};
166
167module_i2c_driver(mcp3021_driver);
168
169MODULE_AUTHOR("Mingkai Hu <Mingkai.hu@freescale.com>");
170MODULE_DESCRIPTION("Microchip MCP3021 driver");
171MODULE_LICENSE("GPL");