On Wed, Aug 24, 2011 at 1:22 AM, MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> wrote:
> Device specific sysfs interface /sys/devices/.../power/devfreq_*
> - governor R: name of governor
> - cur_freq R: current frequency
> - max_freq R: maximum operable frequency
> - min_freq R: minimum operable frequency
> - polling_interval R: polling interval in ms given with devfreq profile
> W: update polling interval.
>
> Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>
> --
> Changed from v7
> - removed set_freq from the common devfreq interface
> - added get_devfreq, a mutex-protected wrapper for find_device_devfreq
> (for sysfs interfaces and later with governor-support)
> - corrected ABI documentation.
>
> Changed from v6
> - poling_interval is writable.
>
> Changed from v5
> - updated devferq_update usage.
>
> Changed from v4
> - removed system-wide sysfs interface
> - removed tickling sysfs interface
> - added set_freq for userspace governor (and any other governors that
> require user input)
>
> Changed from v3
> - corrected sysfs API usage
> - corrected error messages
> - moved sysfs entry location
> - added sysfs entries
>
> Changed from v2
> - add ABI entries for devfreq sysfs interface
> ---
> Documentation/ABI/testing/sysfs-devices-power | 37 ++++++
> drivers/devfreq/devfreq.c | 150 +++++++++++++++++++++++++
> 2 files changed, 187 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
> index 8ffbc25..57f4591 100644
> --- a/Documentation/ABI/testing/sysfs-devices-power
> +++ b/Documentation/ABI/testing/sysfs-devices-power
> @@ -165,3 +165,40 @@ Description:
>
> Not all drivers support this attribute. If it isn't supported,
> attempts to read or write it will yield I/O errors.
> +
> +What: /sys/devices/.../power/devfreq_governor
> +Date: July 2011
> +Contact: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> +Description:
> + The /sys/devices/.../power/devfreq_governor shows the name
> + of the governor used by the corresponding device.
> +
> +What: /sys/devices/.../power/devfreq_cur_freq
> +Date: July 2011
> +Contact: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> +Description:
> + The /sys/devices/.../power/devfreq_cur_freq shows the current
> + frequency of the corresponding device.
> +
> +What: /sys/devices/.../power/devfreq_max_freq
> +Date: July 2011
> +Contact: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> +Description:
> + The /sys/devices/.../power/devfreq_max_freq shows the
> + maximum operable frequency of the corresponding device.
> +
> +What: /sys/devices/.../power/devfreq_min_freq
> +Date: July 2011
> +Contact: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> +Description:
> + The /sys/devices/.../power/devfreq_min_freq shows the
> + minimum operable frequency of the corresponding device.
> +
> +What: /sys/devices/.../power/devfreq_polling_interval
> +Date: July 2011
> +Contact: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> +Description:
> + The /sys/devices/.../power/devfreq_polling_interval sets and
> + shows the requested polling interval of the corresponding
> + device. The values are represented in ms. If the value is less
> + than 1 jiffy, it is considered to be 0, which means no polling.
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index df63bdc..5bbece6 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -37,6 +37,8 @@ static struct delayed_work devfreq_work;
> static LIST_HEAD(devfreq_list);
> static DEFINE_MUTEX(devfreq_list_lock);
>
> +static struct attribute_group dev_attr_group;
> +
> /**
> * find_device_devfreq() - find devfreq struct using device pointer
> * @dev: device pointer used to lookup device devfreq.
> @@ -62,6 +64,22 @@ static struct devfreq *find_device_devfreq(struct device *dev)
> }
>
> /**
> + * get_devfreq() - find devfreq struct. a wrapped find_device_devfreq()
> + * with mutex protection.
> + * @dev: device pointer used to lookup device devfreq.
> + */
> +static struct devfreq *get_devfreq(struct device *dev)
> +{
> + struct devfreq *ret;
> +
> + mutex_lock(&devfreq_list_lock);
> + ret = find_device_devfreq(dev);
> + mutex_unlock(&devfreq_list_lock);
> +
> + return ret;
> +}
Sorry I'll have to rescind my ACK. I just reviewed patch 5/5 and the
show_freq and restore_freq functions for the userspace governor do not
protect the private data accesses with a mutex. Looking a bit further
I see that they do call get_devfreq; I think the semantics for this
are wrong.
get_devfreq only protects the list as long as it takes to do a lookup.
However neither struct devfreq or struct userspace_data have a mutex
associated with them, so concurrent operations are not protected.
One heavy-handed way of solving this is to not have get_devfreq
release the mutex, and then have those functions call a new
put_devfreq which does release the mutex. However that is really bad
locking.
What do you think about putting a mutex in struct devfreq? The rule
for governors can be that access to the governor-specific private data
requires taking that devfreq's mutex.
Regards,
Mike
> +
> +/**
> * devfreq_do() - Check the usage profile of a given device and configure
> * frequency and voltage accordingly
> * @devfreq: devfreq info of the given device
> @@ -149,6 +167,8 @@ static void devfreq_monitor(struct work_struct *work)
> dev_err(devfreq->dev, "Due to devfreq_do error(%d), devfreq(%s) is removed from the device\n",
> error, devfreq->governor->name);
>
> + sysfs_unmerge_group(&devfreq->dev->kobj,
> + &dev_attr_group);
> list_del(&devfreq->node);
> kfree(devfreq);
>
> @@ -239,6 +259,8 @@ int devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile,
> queue_delayed_work(devfreq_wq, &devfreq_work,
> devfreq->next_polling);
> }
> +
> + sysfs_merge_group(&dev->kobj, &dev_attr_group);
> out:
> mutex_unlock(&devfreq_list_lock);
>
> @@ -271,6 +293,8 @@ int devfreq_remove_device(struct device *dev)
> goto out;
> }
>
> + sysfs_unmerge_group(&dev->kobj, &dev_attr_group);
> +
> list_del(&devfreq->node);
> srcu_notifier_chain_unregister(nh, &devfreq->nb);
> kfree(devfreq);
> @@ -279,6 +303,132 @@ out:
> return 0;
> }
>
> +static ssize_t show_governor(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq *df = get_devfreq(dev);
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> + if (!df->governor)
> + return -EINVAL;
> +
> + return sprintf(buf, "%s\n", df->governor->name);
> +}
> +
> +static ssize_t show_freq(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq *df = get_devfreq(dev);
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> +
> + return sprintf(buf, "%lu\n", df->previous_freq);
> +}
> +
> +static ssize_t show_max_freq(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq *df = get_devfreq(dev);
> + unsigned long freq = ULONG_MAX;
> + struct opp *opp;
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> + if (!df->dev)
> + return -EINVAL;
> +
> + opp = opp_find_freq_floor(df->dev, &freq);
> + if (IS_ERR(opp))
> + return PTR_ERR(opp);
> +
> + return sprintf(buf, "%lu\n", freq);
> +}
> +
> +static ssize_t show_min_freq(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq *df = get_devfreq(dev);
> + unsigned long freq = 0;
> + struct opp *opp;
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> + if (!df->dev)
> + return -EINVAL;
> +
> + opp = opp_find_freq_ceil(df->dev, &freq);
> + if (IS_ERR(opp))
> + return PTR_ERR(opp);
> +
> + return sprintf(buf, "%lu\n", freq);
> +}
> +
> +static ssize_t show_polling_interval(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq *df = get_devfreq(dev);
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> + if (!df->profile)
> + return -EINVAL;
> +
> + return sprintf(buf, "%d\n", df->profile->polling_ms);
> +}
> +
> +static ssize_t store_polling_interval(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct devfreq *df = get_devfreq(dev);
> + unsigned int value;
> + int ret;
> +
> + if (IS_ERR(df))
> + return PTR_ERR(df);
> + if (!df->profile)
> + return -EINVAL;
> +
> + ret = sscanf(buf, "%u", &value);
> + if (ret != 1)
> + return -EINVAL;
> +
> + df->profile->polling_ms = value;
> + df->next_polling = df->polling_jiffies
> + = msecs_to_jiffies(value);
> +
> + mutex_lock(&devfreq_list_lock);
> + if (df->next_polling > 0 && !polling) {
> + polling = true;
> + queue_delayed_work(devfreq_wq, &devfreq_work,
> + df->next_polling);
> + }
> + mutex_unlock(&devfreq_list_lock);
> +
> + return count;
> +}
> +
> +static DEVICE_ATTR(devfreq_governor, 0444, show_governor, NULL);
> +static DEVICE_ATTR(devfreq_cur_freq, 0444, show_freq, NULL);
> +static DEVICE_ATTR(devfreq_max_freq, 0444, show_max_freq, NULL);
> +static DEVICE_ATTR(devfreq_min_freq, 0444, show_min_freq, NULL);
> +static DEVICE_ATTR(devfreq_polling_interval, 0644, show_polling_interval,
> + store_polling_interval);
> +static struct attribute *dev_entries[] = {
> + &dev_attr_devfreq_governor.attr,
> + &dev_attr_devfreq_cur_freq.attr,
> + &dev_attr_devfreq_max_freq.attr,
> + &dev_attr_devfreq_min_freq.attr,
> + &dev_attr_devfreq_polling_interval.attr,
> + NULL,
> +};
> +static struct attribute_group dev_attr_group = {
> + .name = power_group_name,
> + .attrs = dev_entries,
> +};
> +
> /**
> * devfreq_init() - Initialize data structure for devfreq framework and
> * start polling registered devfreq devices.
> --
> 1.7.4.1
>
>
_______________________________________________
linux-pm mailing list
linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/linux-pm
