![Kamil Debski](/assets/img/avatar_default.png)
The state of a PWM output is not clearly defined after resume. Some PWM drivers do not restore the duty cycle upon resume, thus it is necessary to manually restore the correct value. Signed-off-by: Kamil Debski <k.debski@samsung.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
201 lines
4.5 KiB
C
201 lines
4.5 KiB
C
/*
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* pwm-fan.c - Hwmon driver for fans connected to PWM lines.
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*
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* Copyright (c) 2014 Samsung Electronics Co., Ltd.
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*
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* Author: Kamil Debski <k.debski@samsung.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/pwm.h>
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#include <linux/sysfs.h>
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#define MAX_PWM 255
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struct pwm_fan_ctx {
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struct mutex lock;
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struct pwm_device *pwm;
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unsigned char pwm_value;
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};
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static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
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unsigned long pwm, duty;
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ssize_t ret;
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if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
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return -EINVAL;
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mutex_lock(&ctx->lock);
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if (ctx->pwm_value == pwm)
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goto exit_set_pwm_no_change;
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if (pwm == 0) {
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pwm_disable(ctx->pwm);
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goto exit_set_pwm;
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}
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duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM);
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ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
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if (ret)
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goto exit_set_pwm_err;
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if (ctx->pwm_value == 0) {
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ret = pwm_enable(ctx->pwm);
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if (ret)
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goto exit_set_pwm_err;
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}
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exit_set_pwm:
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ctx->pwm_value = pwm;
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exit_set_pwm_no_change:
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ret = count;
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exit_set_pwm_err:
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mutex_unlock(&ctx->lock);
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return ret;
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}
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static ssize_t show_pwm(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
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return sprintf(buf, "%u\n", ctx->pwm_value);
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}
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static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, show_pwm, set_pwm, 0);
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static struct attribute *pwm_fan_attrs[] = {
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&sensor_dev_attr_pwm1.dev_attr.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(pwm_fan);
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static int pwm_fan_probe(struct platform_device *pdev)
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{
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struct device *hwmon;
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struct pwm_fan_ctx *ctx;
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int duty_cycle;
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int ret;
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ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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mutex_init(&ctx->lock);
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ctx->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL);
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if (IS_ERR(ctx->pwm)) {
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dev_err(&pdev->dev, "Could not get PWM\n");
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return PTR_ERR(ctx->pwm);
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}
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platform_set_drvdata(pdev, ctx);
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/* Set duty cycle to maximum allowed */
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duty_cycle = ctx->pwm->period - 1;
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ctx->pwm_value = MAX_PWM;
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ret = pwm_config(ctx->pwm, duty_cycle, ctx->pwm->period);
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if (ret) {
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dev_err(&pdev->dev, "Failed to configure PWM\n");
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return ret;
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}
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/* Enbale PWM output */
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ret = pwm_enable(ctx->pwm);
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if (ret) {
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dev_err(&pdev->dev, "Failed to enable PWM\n");
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return ret;
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}
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hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "pwmfan",
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ctx, pwm_fan_groups);
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if (IS_ERR(hwmon)) {
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dev_err(&pdev->dev, "Failed to register hwmon device\n");
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pwm_disable(ctx->pwm);
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return PTR_ERR(hwmon);
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}
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return 0;
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}
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static int pwm_fan_remove(struct platform_device *pdev)
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{
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struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
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if (ctx->pwm_value)
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pwm_disable(ctx->pwm);
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return 0;
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}
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#ifdef CONFIG_PM_SLEEP
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static int pwm_fan_suspend(struct device *dev)
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{
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struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
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if (ctx->pwm_value)
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pwm_disable(ctx->pwm);
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return 0;
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}
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static int pwm_fan_resume(struct device *dev)
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{
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struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
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unsigned long duty;
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int ret;
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if (ctx->pwm_value == 0)
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return 0;
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duty = DIV_ROUND_UP(ctx->pwm_value * (ctx->pwm->period - 1), MAX_PWM);
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ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
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if (ret)
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return ret;
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return pwm_enable(ctx->pwm);
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}
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#endif
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static SIMPLE_DEV_PM_OPS(pwm_fan_pm, pwm_fan_suspend, pwm_fan_resume);
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static struct of_device_id of_pwm_fan_match[] = {
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{ .compatible = "pwm-fan", },
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{},
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};
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static struct platform_driver pwm_fan_driver = {
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.probe = pwm_fan_probe,
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.remove = pwm_fan_remove,
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.driver = {
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.name = "pwm-fan",
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.pm = &pwm_fan_pm,
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.of_match_table = of_pwm_fan_match,
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},
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};
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module_platform_driver(pwm_fan_driver);
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MODULE_AUTHOR("Kamil Debski <k.debski@samsung.com>");
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MODULE_ALIAS("platform:pwm-fan");
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MODULE_DESCRIPTION("PWM FAN driver");
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MODULE_LICENSE("GPL");
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