drivers/hwmon/pwm-fan.c

   1 /*
   2  * pwm-fan.c - Hwmon driver for fans connected to PWM lines.
   3  *
   4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   5  *
   6  * Author: Kamil Debski <k.debski@samsung.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/hwmon.h>
  20 #include <linux/hwmon-sysfs.h>
  21 #include <linux/module.h>
  22 #include <linux/mutex.h>
  23 #include <linux/of.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/pwm.h>
  26 #include <linux/sysfs.h>
  27
  28 #define MAX_PWM 255
  29
  30 struct pwm_fan_ctx {
  31         struct mutex lock;
  32         struct pwm_device *pwm;
  33         unsigned char pwm_value;
  34 };
  35
  36 static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
  37                        const char *buf, size_t count)
  38 {
  39         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
  40         unsigned long pwm, duty;
  41         ssize_t ret;
  42
  43         if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
  44                 return -EINVAL;
  45
  46         mutex_lock(&ctx->lock);
  47
  48         if (ctx->pwm_value == pwm)
  49                 goto exit_set_pwm_no_change;
  50
  51         if (pwm == 0) {
  52                 pwm_disable(ctx->pwm);
  53                 goto exit_set_pwm;
  54         }
  55
  56         duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM);
  57         ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
  58         if (ret)
  59                 goto exit_set_pwm_err;
  60
  61         if (ctx->pwm_value == 0) {
  62                 ret = pwm_enable(ctx->pwm);
  63                 if (ret)
  64                         goto exit_set_pwm_err;
  65         }
  66
  67 exit_set_pwm:
  68         ctx->pwm_value = pwm;
  69 exit_set_pwm_no_change:
  70         ret = count;
  71 exit_set_pwm_err:
  72         mutex_unlock(&ctx->lock);
  73         return ret;
  74 }
  75
  76 static ssize_t show_pwm(struct device *dev,
  77                         struct device_attribute *attr, char *buf)
  78 {
  79         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
  80
  81         return sprintf(buf, "%u\n", ctx->pwm_value);
  82 }
  83
  84
  85 static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, show_pwm, set_pwm, 0);
  86
  87 static struct attribute *pwm_fan_attrs[] = {
  88         &sensor_dev_attr_pwm1.dev_attr.attr,
  89         NULL,
  90 };
  91
  92 ATTRIBUTE_GROUPS(pwm_fan);
  93
  94 static int pwm_fan_probe(struct platform_device *pdev)
  95 {
  96         struct device *hwmon;
  97         struct pwm_fan_ctx *ctx;
  98         int duty_cycle;
  99         int ret;
 100
 101         ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
 102         if (!ctx)
 103                 return -ENOMEM;
 104
 105         mutex_init(&ctx->lock);
 106
 107         ctx->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
 108         if (IS_ERR(ctx->pwm)) {
 109                 dev_err(&pdev->dev, "Could not get PWM\n");
 110                 return PTR_ERR(ctx->pwm);
 111         }
 112
 113         platform_set_drvdata(pdev, ctx);
 114
 115         /* Set duty cycle to maximum allowed */
 116         duty_cycle = ctx->pwm->period - 1;
 117         ctx->pwm_value = MAX_PWM;
 118
 119         ret = pwm_config(ctx->pwm, duty_cycle, ctx->pwm->period);
 120         if (ret) {
 121                 dev_err(&pdev->dev, "Failed to configure PWM\n");
 122                 return ret;
 123         }
 124
 125         /* Enbale PWM output */
 126         ret = pwm_enable(ctx->pwm);
 127         if (ret) {
 128                 dev_err(&pdev->dev, "Failed to enable PWM\n");
 129                 return ret;
 130         }
 131
 132         hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "pwmfan",
 133                                                        ctx, pwm_fan_groups);
 134         if (IS_ERR(hwmon)) {
 135                 dev_err(&pdev->dev, "Failed to register hwmon device\n");
 136                 pwm_disable(ctx->pwm);
 137                 return PTR_ERR(hwmon);
 138         }
 139         return 0;
 140 }
 141
 142 static int pwm_fan_remove(struct platform_device *pdev)
 143 {
 144         struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
 145
 146         if (ctx->pwm_value)
 147                 pwm_disable(ctx->pwm);
 148         return 0;
 149 }
 150
 151 #ifdef CONFIG_PM_SLEEP
 152 static int pwm_fan_suspend(struct device *dev)
 153 {
 154         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 155
 156         if (ctx->pwm_value)
 157                 pwm_disable(ctx->pwm);
 158         return 0;
 159 }
 160
 161 static int pwm_fan_resume(struct device *dev)
 162 {
 163         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 164         unsigned long duty;
 165         int ret;
 166
 167         if (ctx->pwm_value == 0)
 168                 return 0;
 169
 170         duty = DIV_ROUND_UP(ctx->pwm_value * (ctx->pwm->period - 1), MAX_PWM);
 171         ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
 172         if (ret)
 173                 return ret;
 174         return pwm_enable(ctx->pwm);
 175 }
 176 #endif
 177
 178 static SIMPLE_DEV_PM_OPS(pwm_fan_pm, pwm_fan_suspend, pwm_fan_resume);
 179
 180 static struct of_device_id of_pwm_fan_match[] = {
 181         { .compatible = "pwm-fan", },
 182         {},
 183 };
 184
 185 static struct platform_driver pwm_fan_driver = {
 186         .probe          = pwm_fan_probe,
 187         .remove         = pwm_fan_remove,
 188         .driver = {
 189                 .name           = "pwm-fan",
 190                 .pm             = &pwm_fan_pm,
 191                 .of_match_table = of_pwm_fan_match,
 192         },
 193 };
 194
 195 module_platform_driver(pwm_fan_driver);
 196
 197 MODULE_AUTHOR("Kamil Debski <k.debski@samsung.com>");
 198 MODULE_ALIAS("platform:pwm-fan");
 199 MODULE_DESCRIPTION("PWM FAN driver");
 200 MODULE_LICENSE("GPL");