1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * sl28cpld hardware monitoring driver
4 *
5 * Copyright 2020 Kontron Europe GmbH
6 */
7
8#include <linux/bitfield.h>
9#include <linux/hwmon.h>
10#include <linux/kernel.h>
11#include <linux/mod_devicetable.h>
12#include <linux/module.h>
13#include <linux/platform_device.h>
14#include <linux/property.h>
15#include <linux/regmap.h>
16
17#define FAN_INPUT		0x00
18#define   FAN_SCALE_X8		BIT(7)
19#define   FAN_VALUE_MASK	GENMASK(6, 0)
20
21struct sl28cpld_hwmon {
22	struct regmap *regmap;
23	u32 offset;
24};
25
26static umode_t sl28cpld_hwmon_is_visible(const void *data,
27					 enum hwmon_sensor_types type,
28					 u32 attr, int channel)
29{
30	return 0444;
31}
32
33static int sl28cpld_hwmon_read(struct device *dev,
34			       enum hwmon_sensor_types type, u32 attr,
35			       int channel, long *input)
36{
37	struct sl28cpld_hwmon *hwmon = dev_get_drvdata(dev);
38	unsigned int value;
39	int ret;
40
41	switch (attr) {
42	case hwmon_fan_input:
43		ret = regmap_read(hwmon->regmap, hwmon->offset + FAN_INPUT,
44				  &value);
45		if (ret)
46			return ret;
47		/*
48		 * The register has a 7 bit value and 1 bit which indicates the
49		 * scale. If the MSB is set, then the lower 7 bit has to be
50		 * multiplied by 8, to get the correct reading.
51		 */
52		if (value & FAN_SCALE_X8)
53			value = FIELD_GET(FAN_VALUE_MASK, value) << 3;
54
55		/*
56		 * The counter period is 1000ms and the sysfs specification
57		 * says we should assume 2 pulses per revolution.
58		 */
59		value *= 60 / 2;
60
61		break;
62	default:
63		return -EOPNOTSUPP;
64	}
65
66	*input = value;
67	return 0;
68}
69
70static const struct hwmon_channel_info * const sl28cpld_hwmon_info[] = {
71	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
72	NULL
73};
74
75static const struct hwmon_ops sl28cpld_hwmon_ops = {
76	.is_visible = sl28cpld_hwmon_is_visible,
77	.read = sl28cpld_hwmon_read,
78};
79
80static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
81	.ops = &sl28cpld_hwmon_ops,
82	.info = sl28cpld_hwmon_info,
83};
84
85static int sl28cpld_hwmon_probe(struct platform_device *pdev)
86{
87	struct sl28cpld_hwmon *hwmon;
88	struct device *hwmon_dev;
89	int ret;
90
91	if (!pdev->dev.parent)
92		return -ENODEV;
93
94	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
95	if (!hwmon)
96		return -ENOMEM;
97
98	hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
99	if (!hwmon->regmap)
100		return -ENODEV;
101
102	ret = device_property_read_u32(&pdev->dev, "reg", &hwmon->offset);
103	if (ret)
104		return -EINVAL;
105
106	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
107				"sl28cpld_hwmon", hwmon,
108				&sl28cpld_hwmon_chip_info, NULL);
109	if (IS_ERR(hwmon_dev))
110		dev_err(&pdev->dev, "failed to register as hwmon device");
111
112	return PTR_ERR_OR_ZERO(hwmon_dev);
113}
114
115static const struct of_device_id sl28cpld_hwmon_of_match[] = {
116	{ .compatible = "kontron,sl28cpld-fan" },
117	{}
118};
119MODULE_DEVICE_TABLE(of, sl28cpld_hwmon_of_match);
120
121static struct platform_driver sl28cpld_hwmon_driver = {
122	.probe = sl28cpld_hwmon_probe,
123	.driver = {
124		.name = "sl28cpld-fan",
125		.of_match_table = sl28cpld_hwmon_of_match,
126	},
127};
128module_platform_driver(sl28cpld_hwmon_driver);
129
130MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
131MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
132MODULE_LICENSE("GPL");
133