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PM / devfreq: Add sysfs node to expose available frequencies 

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
sets the requested frequency for the devfreq object if
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);
}
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[] = {
__ATTR(governor, S_IRUGO, show_governor, 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(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
store_polling_interval),