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