From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752292Ab2JYXwt (ORCPT ); Thu, 25 Oct 2012 19:52:49 -0400 Received: from ogre.sisk.pl ([193.178.161.156]:37951 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750887Ab2JYXws (ORCPT ); Thu, 25 Oct 2012 19:52:48 -0400 From: "Rafael J. Wysocki" To: Nishanth Menon Cc: linux-pm , Rajagopal Venkat , MyungJoo Ham , Kyungmin Park , Kevin Hilman , linux-kernel@vger.kernel.org Subject: Re: [for-next PATCH] PM / devfreq: Add sysfs node to expose available frequencies Date: Fri, 26 Oct 2012 01:56:44 +0200 Message-ID: <1639482.oGax1ZB8vZ@vostro.rjw.lan> User-Agent: KMail/4.8.5 (Linux/3.6.3-8-desktop; KDE/4.8.5; x86_64; ; ) In-Reply-To: <1351207963-30075-1-git-send-email-nm@ti.com> References: <1351207963-30075-1-git-send-email-nm@ti.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, October 25, 2012 06:32:43 PM Nishanth Menon wrote: > 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 > Cc: MyungJoo Ham > Cc: Kyungmin Park > Cc: "Rafael J. Wysocki" > Cc: Kevin Hilman > Cc: linux-pm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Nishanth Menon > --- > 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 > > Documentation/ABI/testing/sysfs-class-devfreq | 9 +++++++++ > drivers/devfreq/devfreq.c | 26 +++++++++++++++++++++++++ > 2 files changed, 35 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 > +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..2f6ad6b 100644 > --- a/drivers/devfreq/devfreq.c > +++ b/drivers/devfreq/devfreq.c > @@ -571,9 +571,35 @@ 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 += sprintf(&buf[count], "%lu ", freq); > + freq++; > + } while (1); > + rcu_read_unlock(); > + count += sprintf(&buf[count], "\n"); Care to avoid printing the tailing space? Rafael > + > + 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), > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.