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PM / devfreq: Add sysfs node to expose available frequencies

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devfreq governors such as ondemand are controlled by a min and
max frequency, while governors like userspace governor allow us
to set a specific frequency.
However, for the same specific device, depending on the SoC, the
available frequencies can vary.

So expose the available frequencies as a snapshot over sysfs to
allow informed decisions.

This was inspired by cpufreq framework's equivalent for similar
usage sysfs node: scaling_available_frequencies.

Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
This commit is contained in:
Nishanth Menon 2012-10-25 19:48:59 -05:00 committed by MyungJoo Ham
parent e09651fcc2
commit d287de855f
2 changed files with 41 additions and 0 deletions
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9
Documentation/ABI/testing/sysfs-class-devfreq
View File

@ -51,3 +51,12 @@ Description:
The /sys/class/devfreq/.../userspace/set_freq shows and The /sys/class/devfreq/.../userspace/set_freq shows and
sets the requested frequency for the devfreq object if sets the requested frequency for the devfreq object if
userspace governor is in effect. userspace governor is in effect.
What: /sys/class/devfreq/.../available_frequencies
Date: October 2012
Contact: Nishanth Menon <nm@ti.com>
Description:
The /sys/class/devfreq/.../available_frequencies shows
the available frequencies of the corresponding devfreq object.
This is a snapshot of available frequencies and not limited
by the min/max frequency restrictions.

32
drivers/devfreq/devfreq.c
View File

@ -570,9 +570,41 @@ static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq); return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
} }
static ssize_t show_available_freqs(struct device *d,
struct device_attribute *attr,
char *buf)
{
struct devfreq *df = to_devfreq(d);
struct device *dev = df->dev.parent;
struct opp *opp;
ssize_t count = 0;
unsigned long freq = 0;
rcu_read_lock();
do {
opp = opp_find_freq_ceil(dev, &freq);
if (IS_ERR(opp))
break;
count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
"%lu ", freq);
freq++;
} while (1);
rcu_read_unlock();
/* Truncate the trailing space */
if (count)
count--;
count += sprintf(&buf[count], "\n");
return count;
}
static struct device_attribute devfreq_attrs[] = { static struct device_attribute devfreq_attrs[] = {
__ATTR(governor, S_IRUGO, show_governor, NULL), __ATTR(governor, S_IRUGO, show_governor, NULL),
__ATTR(cur_freq, S_IRUGO, show_freq, NULL), __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
__ATTR(available_frequencies, S_IRUGO, show_available_freqs, NULL),
__ATTR(target_freq, S_IRUGO, show_target_freq, NULL), __ATTR(target_freq, S_IRUGO, show_target_freq, NULL),
__ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval, __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
store_polling_interval), store_polling_interval),