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.ven...@linaro.org> Cc: MyungJoo Ham <myungjoo....@samsung.com> Cc: Kyungmin Park <kyungmin.p...@samsung.com> Cc: "Rafael J. Wysocki" <r...@sisk.pl> Cc: Kevin Hilman <khil...@ti.com> Cc: linux...@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Nishanth Menon <n...@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 <n...@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), -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
