Re: [PATCH v3] hwmon: pwm-fan: Add pwm-fan driver

[Varka Bhadram <varkabhadram@gmail.com>]

On 07/15/2014 05:21 PM, Kamil Debski wrote:
> 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>
> ---
> Changes since v2:
> - add CONFIG_PM_SLEEP around pwm_fan_suspend and pwm_fan_resume
> Changes since v1:
> - added documentation to Documentation/hwmon
> - fix checkpatch errors
> 	- added extra description to Kconfig
> 	- removed whitespace errors
> - include files rearranged to be in alphabetical order
> - remove unused sysfs entry pwm1_enable
> - changed the behavior of the set_pwm function
> 	- when 0 PWM value is set pwm_disable is run
> 	- pwm_config return value is checked for errors
> - use of ATTRIBUTE_GROUPS was added
> - removed "Not enouch memory" error message
> - fixed probe return value in case of devm_of_pwm_get error
> - changed hwmon_device_register_with_groups to
>    devm_hwmon_device_register_with_groups
> - changes suspend/resume to use pwm_disable/enable
> - removed unnecessary CONFIG_PM_SLEEP ifdefs
> ---
>   .../devicetree/bindings/hwmon/pwm-fan.txt          |   12 ++
>   Documentation/hwmon/pwm-fan                        |   17 ++
>   drivers/hwmon/Kconfig                              |   11 ++
>   drivers/hwmon/Makefile                             |    1 +
>   drivers/hwmon/pwm-fan.c                            |  201 ++++++++++++++++++++
>   5 files changed, 242 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/hwmon/pwm-fan.txt
>   create mode 100644 Documentation/hwmon/pwm-fan
>   create mode 100644 drivers/hwmon/pwm-fan.c
>
> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> new file mode 100644
> index 0000000..f534607
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> @@ -0,0 +1,12 @@
> +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>;
> +	};
> diff --git a/Documentation/hwmon/pwm-fan b/Documentation/hwmon/pwm-fan
> new file mode 100644
> index 0000000..18529d2
> --- /dev/null
> +++ b/Documentation/hwmon/pwm-fan
> @@ -0,0 +1,17 @@
> +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.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 02d3d85..4ac13ab 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1105,6 +1105,17 @@ 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
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 3dc0f02..3967ecf 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -120,6 +120,7 @@ obj-$(CONFIG_SENSORS_NTC_THERMISTOR)	+= ntc_thermistor.o
>   obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
>   obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o
>   obj-$(CONFIG_SENSORS_PCF8591)	+= pcf8591.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
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> new file mode 100644
> index 0000000..03d45f2
> --- /dev/null
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -0,0 +1,201 @@
> +/*
> + * 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 device *hwmon;
> +	struct mutex lock;
> +	struct platform_device *pdev;
> +	struct pwm_device *pwm;
> +	unsigned int duty_cycle;
> +	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;
> +	int ret;
> +
> +	if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
> +		return -EINVAL;
> +
> +	mutex_lock(&ctx->lock);
> +
> +	if (ctx->pwm_value == pwm)
> +		goto exit_set_pwm;
> +
> +	if (pwm == 0) {
> +		pwm_disable(ctx->pwm);
> +		ctx->pwm_value = 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) {
> +		count = ret; /* Set the return value */
> +		goto exit_set_pwm;
> +	}
> +
> +	if (ctx->pwm_value == 0)
> +		ret = pwm_enable(ctx->pwm);
> +	if (ret) {
> +		count = ret; /* Set the return value */
> +		goto exit_set_pwm;
> +	}
> +
> +	ctx->duty_cycle = duty;
> +	ctx->pwm_value = pwm;
> +
> +exit_set_pwm:
> +	mutex_unlock(&ctx->lock);
> +	return count;
> +}
> +
> +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 pwm_fan_ctx *ctx;
> +	int ret;
> +
> +	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return PTR_ERR(ctx);

return -ENOMEM ????

> +
> +	ctx->pdev = pdev;
> +	mutex_init(&ctx->lock);
> +
> +	ctx->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, 0);
> +	if (IS_ERR(ctx->pwm)) {
> +		dev_err(&pdev->dev, "Could not get PWM");

missed terminating new line '\n'...  :-)

> +		return PTR_ERR(ctx->pwm);
> +	}
> +
> +	dev_set_drvdata(&pdev->dev, ctx);
> +	platform_set_drvdata(pdev, ctx);
> +
> +	/* Set duty cycle to maximum allowed */
> +	ctx->duty_cycle = ctx->pwm->period - 1;
> +	ctx->pwm_value = MAX_PWM;
> +
> +	ret = pwm_config(ctx->pwm, ctx->duty_cycle, ctx->pwm->period);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to configure PWM");

here...

> +		return ret;
> +	}
> +
> +	/* Enbale PWM output */
> +	ret = pwm_enable(ctx->pwm);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to enable PWM");

here...

> +		return ret;
> +	}
> +
> +	ctx->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
> +						"pwmfan", ctx, pwm_fan_groups);

should match open parenthesis...

ctx->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev,
						    "pwmfan", ctx,
						    pwm_fan_groups);

> +
> +	if (IS_ERR(ctx->hwmon)) {
> +		dev_err(&pdev->dev, "Failed to register hwmon device");

forgot '\n'

> +		pwm_disable(ctx->pwm);
> +		return PTR_ERR(ctx->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_match_ptr(of_pwm_fan_match),

This driver will always populate through the dts file. So no need
of using 'of_match_ptr' here.

> +	},
> +};
> +
> +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");


-- 
Regards,
Varka Bhadram.