Date:	Sun, 3 Jul 2011 00:13:10 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	MyungJoo Ham <myungjoo.ham@...sung.com>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Jiejing Zhang <kzjeef@...il.com>,
	Colin Cross <ccross@...gle.com>, Nishanth Menon <nm@...com>,
	Thomas Gleixner <tglx@...utronix.de>, myungjoo.ham@...il.com
Subject: Re: [PATCH v3 3/3] PM / DEVFREQ: add sysfs interface (including user tickling)

On Friday, May 27, 2011, MyungJoo Ham wrote:
> 1. System-wide sysfs interface
> - tickle_all	R: number of tickle_all execution
> 		W: tickle all devfreq devices
> - min_interval	R: devfreq monitoring base interval in ms
> - monitoring	R: shows whether devfreq monitoring is active or
>   not.
> 
> 2. Device specific sysfs interface
> - tickle	R: number of tickle execution for the device
> 		W: tickle the device
> 
> Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@...sung.com>
> 
> --
> Changed from v2
> - add ABI entries for devfreq sysfs interface
> ---
>  Documentation/ABI/testing/sysfs-devices-devfreq |   21 ++++
>  Documentation/ABI/testing/sysfs-power           |   43 ++++++++
>  drivers/base/power/devfreq.c                    |  133 ++++++++++++++++++++++-
>  include/linux/devfreq.h                         |    3 +
>  4 files changed, 199 insertions(+), 1 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-devfreq
> 
> diff --git a/Documentation/ABI/testing/sysfs-devices-devfreq b/Documentation/ABI/testing/sysfs-devices-devfreq
> new file mode 100644
> index 0000000..7f35a64
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-devices-devfreq
> @@ -0,0 +1,21 @@
> +What:		/sys/devices/.../devfreq/
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/device/.../devfreq directory will contain files
> +		that provide interfaces to DEVFREQ for a specific device.
> +
> +What:		/sys/devices/.../devfreq/tickle
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/devices/.../devfreq/tickle file allows user space
> +		to force the corresponding device to operate at its maximum
> +		operable frequency instaneously and temporarily. After a
> +		designated duration has passed, the operating frequency returns
> +		to normal. When a user reads the tickle entry, it returns
> +		the number of tickle executions for the device. When a user
> +		writes to the tickle entry with the tickle duration in ms,
> +		the effect of device tickling is held for the designated
> +		duration. Note that the duration is rounded-up by
> +		the value DEVFREQ_INTERVAL defined in devfreq.c
> diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
> index b464d12..4d8434b 100644
> --- a/Documentation/ABI/testing/sysfs-power
> +++ b/Documentation/ABI/testing/sysfs-power
> @@ -172,3 +172,46 @@ Description:
>  
>  		Reading from this file will display the current value, which is
>  		set to 1 MB by default.
> +
> +What:		/sys/power/devfreq/
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/power/devfreq directory will contain files that will
> +		provide a unified interface to the DEVFREQ, a generic DVFS
> +		(dynamic voltage and frequency scaling) framework.
> +
> +What:		/sys/power/devfreq/tickle_all
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/power/devfreq/tickle_all file allows user space to
> +		force every device with DEVFREQ to operate at the maximum
> +		frequency of the device instaneously and temporarily. After
> +		a designated delay has passed, the operating frequency returns
> +		to normal. If a user reads the tickle_all entry, it returns
> +		the number of tickle_all executions. When writing to the
> +		tickle_all entry, the user should supply with the duration of
> +		tickle in ms (the "designated delay" mentioned before). Then,
> +		the effect of tickle_all will hold for the denoted duration.
> +		Note that the duration is rounded by the monitoring period
> +		defined by DEVFREQ_INTERVAL in /drivers/base/power/devfreq.c.
> +
> +What:		/sys/power/devfreq/min_interval
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/power/devfreq/min_interval file shows the monitoring
> +		period defined by DEVFREQ_INTERVAL in
> +		/drivers/base/power/devfreq.c. The duration of device tickling
> +		is rounded-up by DEVFREQ_INTERVAL.
> +
> +What:		/sys/power/devfreq/monitoring
> +Date:		May 2011
> +Contact:	MyungJoo Ham <myungjoo.ham@...sung.com>
> +Description:
> +		The /sys/power/devfreq/monitoring file shows whether DEVFREQ
> +		is periodically monitoring. Periodic monitoring is activated
> +		if there is a device that wants periodic monitoring for DVFS or
> +		there is a device that is tickled (and the tickling duration is
> +		not yet expired).
> diff --git a/drivers/base/power/devfreq.c b/drivers/base/power/devfreq.c
> index 7648a94..709c138 100644
> --- a/drivers/base/power/devfreq.c
> +++ b/drivers/base/power/devfreq.c
> @@ -40,6 +40,9 @@ static LIST_HEAD(devfreq_list);
>  /* Exclusive access to devfreq_list and its elements */
>  static DEFINE_MUTEX(devfreq_list_lock);
>  
> +static struct kobject *devfreq_kobj;
> +static struct attribute_group dev_attr_group;
> +
>  /**
>   * find_device_devfreq() - find devfreq struct using device pointer
>   * @dev:	device pointer used to lookup device DEVFREQ.
> @@ -237,6 +240,8 @@ int devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile,
>  		queue_delayed_work(devfreq_wq, &devfreq_work,
>  				   msecs_to_jiffies(DEVFREQ_INTERVAL));
>  	}
> +
> +	sysfs_update_group(&dev->kobj, &dev_attr_group);

This appears to modify the attributes of the device, but anything like it is
not mentioned in the documentation.  What's up?

>  out:
>  	mutex_unlock(&devfreq_list_lock);
>  
> @@ -263,6 +268,8 @@ int devfreq_remove_device(struct device *dev)
>  		return -EINVAL;
>  	}
>  
> +	sysfs_remove_group(&dev->kobj, &dev_attr_group);
> +
>  	list_del(&devfreq->node);
>  
>  	kfree(devfreq);
> @@ -344,7 +351,7 @@ static int _devfreq_tickle_device(struct devfreq *df, unsigned long delay)
>  	if (devfreq_wq && !polling) {
>  		polling = true;
>  		queue_delayed_work(devfreq_wq, &devfreq_work,
> -				msecs_to_jiffies(DEVFREQ_INTERVAL));
> +				   msecs_to_jiffies(DEVFREQ_INTERVAL));

This change doesn't seem to belong to this patch.

>  	}
>  
>  	return err;
> @@ -382,6 +389,116 @@ int devfreq_tickle_device(struct device *dev, unsigned long duration_ms)
>  	return err;
>  }
>  
> +static int num_tickle_all;
> +static ssize_t tickle_all(struct device *dev, struct device_attribute *attr,
> +			  const char *buf, size_t count)
> +{
> +	int duration = 0;
> +	struct devfreq *tmp;
> +	unsigned long delay;
> +
> +	sscanf(buf, "%d", &duration);
> +	if (duration < DEVFREQ_INTERVAL)
> +		duration = DEVFREQ_INTERVAL;
> +
> +	if (unlikely(IS_ERR_OR_NULL(dev))) {
> +		pr_err("%s: Invalid parameters\n", __func__);

Please say "null device" instead of in addition to the above.

> +		return -EINVAL;
> +	}
> +
> +	delay = DIV_ROUND_UP(duration, DEVFREQ_INTERVAL);
> +
> +	mutex_lock(&devfreq_list_lock);
> +	list_for_each_entry(tmp, &devfreq_list, node) {
> +		_devfreq_tickle_device(tmp, delay);
> +	}
> +	mutex_unlock(&devfreq_list_lock);
> +
> +	num_tickle_all++;
> +	return count;
> +}
> +
> +static ssize_t show_num_tickle_all(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", num_tickle_all);
> +}
> +
> +static ssize_t show_min_interval(struct device *dev,
> +				 struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", DEVFREQ_INTERVAL);
> +}
> +
> +static ssize_t show_monitoring(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", monitoring ? 1 : 0);
> +}
> +
> +static DEVICE_ATTR(tickle_all, 0644, show_num_tickle_all, tickle_all);
> +static DEVICE_ATTR(min_interval, 0444, show_min_interval, NULL);
> +static DEVICE_ATTR(monitoring, 0444, show_monitoring, NULL);
> +static struct attribute *devfreq_entries[] = {
> +	&dev_attr_tickle_all.attr,
> +	&dev_attr_min_interval.attr,
> +	&dev_attr_monitoring.attr,
> +	NULL,
> +};
> +static struct attribute_group devfreq_attr_group = {
> +	.name	= NULL,
> +	.attrs	= devfreq_entries,
> +};
> +
> +static ssize_t tickle(struct device *dev, struct device_attribute *attr,
> +		      const char *buf, size_t count)
> +{
> +	int duration;
> +	struct devfreq *df;
> +	unsigned long delay;
> +
> +	sscanf(buf, "%d", &duration);
> +	if (duration < DEVFREQ_INTERVAL)
> +		duration = DEVFREQ_INTERVAL;
> +
> +	if (unlikely(IS_ERR_OR_NULL(dev))) {
> +		pr_err("%s: Invalid parameters\n", __func__);

Like above.

> +		return -EINVAL;
> +	}
> +
> +	delay = DIV_ROUND_UP(duration, DEVFREQ_INTERVAL);
> +
> +	mutex_lock(&devfreq_list_lock);
> +	df = find_device_devfreq(dev);
> +	_devfreq_tickle_device(df, delay);
> +	mutex_unlock(&devfreq_list_lock);
> +
> +	return count;
> +}
> +
> +static ssize_t show_num_tickle(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct devfreq *df;
> +
> +	df = find_device_devfreq(dev);
> +
> +	if (!IS_ERR(df))
> +		return sprintf(buf, "%d\n", df->num_tickle);
> +
> +	return PTR_ERR(df);
> +}
> +
> +static DEVICE_ATTR(tickle, 0644, show_num_tickle, tickle);
> +static struct attribute *dev_entries[] = {
> +	&dev_attr_tickle.attr,
> +	NULL,
> +};
> +static struct attribute_group dev_attr_group = {
> +	.name	= "devfreq",
> +	.attrs	= dev_entries,
> +};
> +
>  static int __init devfreq_init(void)
>  {
>  	mutex_lock(&devfreq_list_lock);
> @@ -389,6 +506,20 @@ static int __init devfreq_init(void)
>  	polling = false;
>  	devfreq_wq = create_freezable_workqueue("devfreq_wq");
>  	INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
> +
> +#ifdef CONFIG_PM
> +	/* Create sysfs */
> +	devfreq_kobj = kobject_create_and_add("devfreq", power_kobj);

Hmm, so power_kobj is global?  It shouldn't be.

Generally, whatever adds attributes to /sys/power should be located in
kernel/power/ .

> +	if (!devfreq_kobj) {
> +		pr_err("Unable to create DEVFREQ kobject.\n");
> +		goto out;
> +	}
> +	if (sysfs_create_group(devfreq_kobj, &devfreq_attr_group)) {
> +		pr_err("Unable to create DEVFREQ sysfs entries.\n");
> +		goto out;
> +	}
> +#endif
> +out:
>  	mutex_unlock(&devfreq_list_lock);
>  
>  	devfreq_monitor(&devfreq_work.work);
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 1ec9a40..69334e7 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -59,6 +59,7 @@ struct devfreq_governor {
>   *		at each executino of devfreq_monitor, tickle is decremented.
>   *		User may tickle a device-devfreq in order to set maximum
>   *		frequency instaneously with some guaranteed duration.
> + * @num_tickle	number of tickle calls.
>   *
>   * This structure stores the DEVFREQ information for a give device.
>   */
> @@ -72,6 +73,8 @@ struct devfreq {
>  	unsigned long previous_freq;
>  	unsigned int next_polling;
>  	unsigned int tickle;
> +
> +	unsigned int num_tickle;
>  };
>  
>  #if defined(CONFIG_PM_DEVFREQ)

It looks like the above two changes should be moved to a separate patch.

Thanks,
Rafael
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