[for-next PATCH V2] PM / devfreq: Add sysfs node to expose available frequencies
From: Nishanth Menon <nm@ti.com>
Date: 2012-10-26 00:49:16
Also in:
lkml
Subsystem:
device frequency (devfreq), the rest · Maintainers:
MyungJoo Ham, Kyungmin Park, Chanwoo Choi, Linus Torvalds
Possibly related (same subject, not in this thread)
- 2012-10-31 · Re: [for-next PATCH V2] PM / devfreq: Add sysfs node to expose available frequencies · Rafael J. Wysocki <hidden>
- 2012-10-31 · Re: Re: [for-next PATCH V2] PM / devfreq: Add sysfs node to expose available frequencies · MyungJoo Ham <myungjoo.ham@samsung.com>
- 2012-10-31 · Re: [for-next PATCH V2] PM / devfreq: Add sysfs node to expose available frequencies · Rafael J. Wysocki <hidden>
- 2012-10-26 · Re: [for-next PATCH V2] PM / devfreq: Add sysfs node to expose available frequencies · MyungJoo Ham <myungjoo.ham@samsung.com>
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 <redacted> Cc: MyungJoo Ham <myungjoo.ham@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Cc: "Rafael J. Wysocki" <redacted> Cc: Kevin Hilman <redacted> Cc: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Nishanth Menon <nm@ti.com> --- Applies on top of Rafael's linux-next branch: git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next b960e9a Merge branch 'pm-sleep-next' into linux-next Example output from Beagleboard XM (3730) using a dummy test driver http://pastebin.pandaboard.org/index.php/view/85100576 : /sys/devices/platform/iva.0/devfreq/iva.0 # cat available_frequencies 260000000 520000000 660000000 /sys/devices/platform/iva.0/devfreq/iva.0 # cat available_frequencies|tr ' ' '-' 260000000-520000000-660000000 V2 : - review comment update from v1 - protected the sysfs from buffer overflow - just in case.. V1: https://patchwork.kernel.org/patch/1648001/ Documentation/ABI/testing/sysfs-class-devfreq | 9 +++++++ drivers/devfreq/devfreq.c | 32 +++++++++++++++++++++++++ 2 files changed, 41 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index e6cf08e..e672ccb 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq@@ -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.
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index d02ee7e..104018e 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c@@ -571,9 +571,41 @@ 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),
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