Re: [PATCH v3 3/3] PM / DEVFREQ: add sysfs interface (including user tickling)

[MyungJoo Ham <myungjoo.ham@samsung.com>]

Hello,

2011/7/3 Rafael J. Wysocki <rjw@sisk.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@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.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@samsung.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@samsung.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@samsung.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@samsung.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@samsung.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@samsung.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".

>
>>  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.

>
>> +             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.

>
> 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.

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.

>
> Thanks,
> Rafael
>


Thank you,
- MyungJoo
-- 
MyungJoo Ham (함명주), Ph.D.
Mobile Software Platform Lab,
Digital Media and Communications (DMC) Business
Samsung Electronics
cell: 82-10-6714-2858
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