hwmon: Add pwm-fan driver

The pwm-fan driver enables control of fans connected to PWM lines.
This driver uses the PWM framework, so it is compatible with all
PWM devices that provide drivers through the PWM framework.
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Reviewed-by: Varka Bhadram <varkabhadram@gmail.com>
Reviewed-by: Tobias Klauser <tklauser@distanz.ch>
[Guenter Roeck: Last argument to devm_of_pwm_get is pointer, use NULL]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/pwm-fan.txt

+Bindings for a fan connected to the PWM lines
+
+Required properties:
+- compatible	: "pwm-fan"
+- pwms		: the PWM that is used to control the PWM fan
+
+Example:
+	pwm-fan {
+		compatible = "pwm-fan";
+		status = "okay";
+		pwms = <&pwm 0 10000 0>;
+	};

Documentation/hwmon/pwm-fan

+Kernel driver pwm-fan
+=====================
+
+This driver enables the use of a PWM module to drive a fan. It uses the
+generic PWM interface thus it is hardware independent. It can be used on
+many SoCs, as long as the SoC supplies a PWM line driver that exposes
+the generic PWM API.
+
+Author: Kamil Debski <k.debski@samsung.com>
+
+Description
+-----------
+
+The driver implements a simple interface for driving a fan connected to
+a PWM output. It uses the generic PWM interface, thus it can be used with
+a range of SoCs. The driver exposes the fan to the user space through
+the hwmon's sysfs interface.

drivers/hwmon/Kconfig

@@ -1128,6 +1128,17 @@ config SENSORS_PCF8591
 
 source drivers/hwmon/pmbus/Kconfig
 
+config SENSORS_PWM_FAN
+	tristate "PWM fan"
+	depends on PWM
+	help
+	  If you say yes here you get support for fans connected to PWM lines.
+	  The driver uses the generic PWM interface, thus it will work on a
+	  variety of SoCs.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called pwm-fan.
+
 config SENSORS_SHT15
 	tristate "Sensiron humidity and temperature sensors. SHT15 and compat."
 	depends on GPIOLIB

drivers/hwmon/Makefile

@@ -122,6 +122,7 @@ obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
 obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o
 obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.o
 obj-$(CONFIG_SENSORS_POWR1220)  += powr1220.o
+obj-$(CONFIG_SENSORS_PWM_FAN)	+= pwm-fan.o
 obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o
 obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
 obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o

drivers/hwmon/pwm-fan.c

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