linux/drivers/hwmon/ltq-cputemp.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* Lantiq cpu temperature sensor driver
   3 *
   4 * Copyright (C) 2017 Florian Eckert <fe@dev.tdt.de>
   5 */
   6
   7#include <linux/bitops.h>
   8#include <linux/delay.h>
   9#include <linux/hwmon.h>
  10#include <linux/hwmon-sysfs.h>
  11#include <linux/init.h>
  12#include <linux/module.h>
  13#include <linux/of_device.h>
  14
  15#include <lantiq_soc.h>
  16
  17/* gphy1 configuration register contains cpu temperature */
  18#define CGU_GPHY1_CR   0x0040
  19#define CGU_TEMP_PD    BIT(19)
  20
  21static void ltq_cputemp_enable(void)
  22{
  23        ltq_cgu_w32(ltq_cgu_r32(CGU_GPHY1_CR) | CGU_TEMP_PD, CGU_GPHY1_CR);
  24}
  25
  26static void ltq_cputemp_disable(void *data)
  27{
  28        ltq_cgu_w32(ltq_cgu_r32(CGU_GPHY1_CR) & ~CGU_TEMP_PD, CGU_GPHY1_CR);
  29}
  30
  31static int ltq_read(struct device *dev, enum hwmon_sensor_types type,
  32                    u32 attr, int channel, long *temp)
  33{
  34        int value;
  35
  36        switch (attr) {
  37        case hwmon_temp_input:
  38                /* get the temperature including one decimal place */
  39                value = (ltq_cgu_r32(CGU_GPHY1_CR) >> 9) & 0x01FF;
  40                value = value * 5;
  41                /* range -38 to +154 \xC2\xB0C, register value zero is -38.0 \xC2\xB0C */
  42                value -= 380;
  43                /* scale temp to millidegree */
  44                value = value * 100;
  45                break;
  46        default:
  47                return -EOPNOTSUPP;
  48        }
  49
  50        *temp = value;
  51        return 0;
  52}
  53
  54static umode_t ltq_is_visible(const void *_data, enum hwmon_sensor_types type,
  55                              u32 attr, int channel)
  56{
  57        if (type != hwmon_temp)
  58                return 0;
  59
  60        switch (attr) {
  61        case hwmon_temp_input:
  62                return 0444;
  63        default:
  64                return 0;
  65        }
  66}
  67
  68static const struct hwmon_channel_info *ltq_info[] = {
  69        HWMON_CHANNEL_INFO(chip,
  70                           HWMON_C_REGISTER_TZ),
  71        HWMON_CHANNEL_INFO(temp,
  72                           HWMON_T_INPUT),
  73        NULL
  74};
  75
  76static const struct hwmon_ops ltq_hwmon_ops = {
  77        .is_visible = ltq_is_visible,
  78        .read = ltq_read,
  79};
  80
  81static const struct hwmon_chip_info ltq_chip_info = {
  82        .ops = &ltq_hwmon_ops,
  83        .info = ltq_info,
  84};
  85
  86static int ltq_cputemp_probe(struct platform_device *pdev)
  87{
  88        struct device *hwmon_dev;
  89        int err = 0;
  90
  91        /* available on vr9 v1.2 SoCs only */
  92        if (ltq_soc_type() != SOC_TYPE_VR9_2)
  93                return -ENODEV;
  94
  95        err = devm_add_action(&pdev->dev, ltq_cputemp_disable, NULL);
  96        if (err)
  97                return err;
  98
  99        ltq_cputemp_enable();
 100
 101        hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
 102                                                         "ltq_cputemp",
 103                                                         NULL,
 104                                                         &ltq_chip_info,
 105                                                         NULL);
 106
 107        if (IS_ERR(hwmon_dev)) {
 108                dev_err(&pdev->dev, "Failed to register as hwmon device");
 109                return PTR_ERR(hwmon_dev);
 110        }
 111
 112        return 0;
 113}
 114
 115const struct of_device_id ltq_cputemp_match[] = {
 116        { .compatible = "lantiq,cputemp" },
 117        {},
 118};
 119MODULE_DEVICE_TABLE(of, ltq_cputemp_match);
 120
 121static struct platform_driver ltq_cputemp_driver = {
 122        .probe = ltq_cputemp_probe,
 123        .driver = {
 124                .name = "ltq-cputemp",
 125                .of_match_table = ltq_cputemp_match,
 126        },
 127};
 128
 129module_platform_driver(ltq_cputemp_driver);
 130
 131MODULE_AUTHOR("Florian Eckert <fe@dev.tdt.de>");
 132MODULE_DESCRIPTION("Lantiq cpu temperature sensor driver");
 133MODULE_LICENSE("GPL");
 134