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Message-Id: <201107041048.46969.rjw@sisk.pl>
Date: Mon, 4 Jul 2011 10:48:46 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: myungjoo.ham@...il.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>
Subject: Re: [PATCH v3 3/3] PM / DEVFREQ: add sysfs interface (including user tickling)
On Monday, July 04, 2011, MyungJoo Ham wrote:
> Hello,
>
> 2011/7/3 Rafael J. Wysocki <rjw@...k.pl>:
> > 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?
>
> It is mentioned "Documentation/ABI/testing/sysfs-devices-devfreq".
Yes, it is, sorry. But it should be under /sys/devices/.../power/ .
> >
> >> 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.
>
> Oops. I'll rearrange the patch series.
>
> >
> >> }
> >>
> >> 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.
>
> Ok. I'll let it say "Null or invalid device" as it's IS_ERR_OR_NULL.
OK
> >
> >> + 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.
>
> Yup.
>
> >
> >> + 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.
>
> Yes, it is global and it's declared at include/linux/kobject.h.
Oh, well.
> >
> > Generally, whatever adds attributes to /sys/power should be located in
> > kernel/power/ .
>
> I've put it at /sys/power because these attributes are global to every
> device with devfreq.
That's fine.
What I wanted to say was that all code adding attributes into /sys/power
should be located under kernel/power/ in the kernel source tree.
Otherwise we'll end up with a mess of dependencies that's hard to maintain.
> Anyway, if you think that's a weird location for it, could you please
> give me some hints on where would be proper to locate system-wide
> devfreq sysfs attributes?
> Or, do you think kernel/power/devfreq.c would be a proper location for devfreq?
>
> Or, what about allowing every /sys/devices/.../devfreq/global/* to be
> the same "global" attributes of devfreq?
>
> >
> >> + 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.
>
> These two changes are for the sysfs interface as counting number of
> tickle is added with sysfs interface.
OK
Thanks,
Rafael
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