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 *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");