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 
21 struct sl28cpld_hwmon {
22 	struct regmap *regmap;
23 	u32 offset;
24 };
25 
26 static 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 
33 static 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 
70 static const struct hwmon_channel_info *sl28cpld_hwmon_info[] = {
71 	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
72 	NULL
73 };
74 
75 static const struct hwmon_ops sl28cpld_hwmon_ops = {
76 	.is_visible = sl28cpld_hwmon_is_visible,
77 	.read = sl28cpld_hwmon_read,
78 };
79 
80 static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
81 	.ops = &sl28cpld_hwmon_ops,
82 	.info = sl28cpld_hwmon_info,
83 };
84 
85 static 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 
115 static const struct of_device_id sl28cpld_hwmon_of_match[] = {
116 	{ .compatible = "kontron,sl28cpld-fan" },
117 	{}
118 };
119 MODULE_DEVICE_TABLE(of, sl28cpld_hwmon_of_match);
120 
121 static 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 };
128 module_platform_driver(sl28cpld_hwmon_driver);
129 
130 MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
131 MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
132 MODULE_LICENSE("GPL");
133