Douglas Anderson, recently pointed out an interesting problem due to which
udelay() was expiring earlier than it should.
While transitioning between frequencies few platforms may temporarily switch to
a stable frequency, waiting for the main PLL to stabilize.
For example: When we transition between very low frequencies on exynos, like
between 200MHz and 300MHz, we may temporarily switch to a PLL running at 800MHz.
No CPUFREQ notification is sent for that. That means there's a period of time
when we're running at 800MHz but loops_per_jiffy is calibrated at between 200MHz
and 300MHz. And so udelay behaves badly.
To get this fixed in a generic way, introduce another set of callbacks
get_intermediate() and target_intermediate(), only for drivers with
target_index() and CPUFREQ_ASYNC_NOTIFICATION unset.
get_intermediate() should return a stable intermediate frequency platform wants
to switch to, and target_intermediate() should set CPU to that frequency,
before jumping to the frequency corresponding to 'index'. Core will take care of
sending notifications and driver doesn't have to handle them in
target_intermediate() or target_index().
NOTE: ->target_index() should restore to policy->restore_freq in case of
failures as core would send notifications for that.
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CPUFreq specific helper functions for OPP (Operating Performance Points)
now use generic OPP functions that allow CPUFreq to be be moved back
into CPUFreq framework. This allows for independent modifications
or future enhancements as needed isolated to just CPUFreq framework
alone.
Here, we just move relevant code and documentation to make this part of
CPUFreq infrastructure.
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
There has been confusion all the time about which mailing list to follow
for cpufreq activities, linux-pm@vger.kernel.org or cpufreq@vger.kernel.org.
Since patches sent to cpufreq@vger.kernel.org don't go to Patchwork
which is a maintenance workflow problem, make linux-pm@vger.kernel.org
the official mailing list for cpufreq stuff and remove all references
of cpufreq@vger.kernel.org from kernel source.
Later, we can request that the list be dropped entirely.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Many cpufreq drivers need to iterate over the cpufreq_frequency_table
for various tasks.
This patch introduces two macros which can be used for iteration over
cpufreq_frequency_table keeping a common coding style across drivers:
- cpufreq_for_each_entry: iterate over each entry of the table
- cpufreq_for_each_valid_entry: iterate over each entry that contains
a valid frequency.
It should have no functional changes.
Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This callback allows the driver to do clean up before the CPU is
completely down and its state cannot be modified. This is used
by the intel_pstate driver to reduce the requested P state prior to
the core going away. This is required because the requested P state
of the offline core is used to select the package P state. This
effectively sets the floor package P state to the requested P state on
the offline core.
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
[rjw: Minor modifications]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Two cpufreq notifiers CPUFREQ_RESUMECHANGE and CPUFREQ_SUSPENDCHANGE have
not been used for some time, so remove them to clean up code a bit.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Since the support for software and hardware controlled boosting has
been added, update the corresponding documentation.
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The Intel P-state driver is currently undocumented. Add some
documentation based on the cover-letter sent with the original series.
Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Currently, the prototype of cpufreq_drivers target routines is:
int target(struct cpufreq_policy *policy, unsigned int target_freq,
unsigned int relation);
And most of the drivers call cpufreq_frequency_table_target() to get a valid
index of their frequency table which is closest to the target_freq. And they
don't use target_freq and relation after that.
So, it makes sense to just do this work in cpufreq core before calling
cpufreq_frequency_table_target() and simply pass index instead. But this can be
done only with drivers which expose their frequency table with cpufreq core. For
others we need to stick with the old prototype of target() until those drivers
are converted to expose frequency tables.
This patch implements the new light weight prototype for target_index() routine.
It looks like this:
int target_index(struct cpufreq_policy *policy, unsigned int index);
CPUFreq core will call cpufreq_frequency_table_target() before calling this
routine and pass index to it. Because CPUFreq core now requires to call routines
present in freq_table.c CONFIG_CPU_FREQ_TABLE must be enabled all the time.
This also marks target() interface as deprecated. So, that new drivers avoid
using it. And Documentation is updated accordingly.
It also converts existing .target() to newly defined light weight
.target_index() routine for many driver.
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Russell King <linux@arm.linux.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rjw@rjwysocki.net>
We don't need to set .owner = THIS_MODULE any more in cpufreq drivers
as this field isn't used any more by the cpufreq core.
This patch removes it and updates all dependent drivers accordingly.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The "index" field of struct cpufreq_frequency_table was never an
index and isn't used at all by the cpufreq core. It only is useful
for cpufreq drivers for their internal purposes.
Many people nowadays blindly set it in ascending order with the
assumption that the core will use it, which is a mistake.
Rename it to "driver_data" as that's what its purpose is. All of its
users are updated accordingly.
[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pull 'full dynticks' support from Ingo Molnar:
"This tree from Frederic Weisbecker adds a new, (exciting! :-) core
kernel feature to the timer and scheduler subsystems: 'full dynticks',
or CONFIG_NO_HZ_FULL=y.
This feature extends the nohz variable-size timer tick feature from
idle to busy CPUs (running at most one task) as well, potentially
reducing the number of timer interrupts significantly.
This feature got motivated by real-time folks and the -rt tree, but
the general utility and motivation of full-dynticks runs wider than
that:
- HPC workloads get faster: CPUs running a single task should be able
to utilize a maximum amount of CPU power. A periodic timer tick at
HZ=1000 can cause a constant overhead of up to 1.0%. This feature
removes that overhead - and speeds up the system by 0.5%-1.0% on
typical distro configs even on modern systems.
- Real-time workload latency reduction: CPUs running critical tasks
should experience as little jitter as possible. The last remaining
source of kernel-related jitter was the periodic timer tick.
- A single task executing on a CPU is a pretty common situation,
especially with an increasing number of cores/CPUs, so this feature
helps desktop and mobile workloads as well.
The cost of the feature is mainly related to increased timer
reprogramming overhead when a CPU switches its tick period, and thus
slightly longer to-idle and from-idle latency.
Configuration-wise a third mode of operation is added to the existing
two NOHZ kconfig modes:
- CONFIG_HZ_PERIODIC: [formerly !CONFIG_NO_HZ], now explicitly named
as a config option. This is the traditional Linux periodic tick
design: there's a HZ tick going on all the time, regardless of
whether a CPU is idle or not.
- CONFIG_NO_HZ_IDLE: [formerly CONFIG_NO_HZ=y], this turns off the
periodic tick when a CPU enters idle mode.
- CONFIG_NO_HZ_FULL: this new mode, in addition to turning off the
tick when a CPU is idle, also slows the tick down to 1 Hz (one
timer interrupt per second) when only a single task is running on a
CPU.
The .config behavior is compatible: existing !CONFIG_NO_HZ and
CONFIG_NO_HZ=y settings get translated to the new values, without the
user having to configure anything. CONFIG_NO_HZ_FULL is turned off by
default.
This feature is based on a lot of infrastructure work that has been
steadily going upstream in the last 2-3 cycles: related RCU support
and non-periodic cputime support in particular is upstream already.
This tree adds the final pieces and activates the feature. The pull
request is marked RFC because:
- it's marked 64-bit only at the moment - the 32-bit support patch is
small but did not get ready in time.
- it has a number of fresh commits that came in after the merge
window. The overwhelming majority of commits are from before the
merge window, but still some aspects of the tree are fresh and so I
marked it RFC.
- it's a pretty wide-reaching feature with lots of effects - and
while the components have been in testing for some time, the full
combination is still not very widely used. That it's default-off
should reduce its regression abilities and obviously there are no
known regressions with CONFIG_NO_HZ_FULL=y enabled either.
- the feature is not completely idempotent: there is no 100%
equivalent replacement for a periodic scheduler/timer tick. In
particular there's ongoing work to map out and reduce its effects
on scheduler load-balancing and statistics. This should not impact
correctness though, there are no known regressions related to this
feature at this point.
- it's a pretty ambitious feature that with time will likely be
enabled by most Linux distros, and we'd like you to make input on
its design/implementation, if you dislike some aspect we missed.
Without flaming us to crisp! :-)
Future plans:
- there's ongoing work to reduce 1Hz to 0Hz, to essentially shut off
the periodic tick altogether when there's a single busy task on a
CPU. We'd first like 1 Hz to be exposed more widely before we go
for the 0 Hz target though.
- once we reach 0 Hz we can remove the periodic tick assumption from
nr_running>=2 as well, by essentially interrupting busy tasks only
as frequently as the sched_latency constraints require us to do -
once every 4-40 msecs, depending on nr_running.
I am personally leaning towards biting the bullet and doing this in
v3.10, like the -rt tree this effort has been going on for too long -
but the final word is up to you as usual.
More technical details can be found in Documentation/timers/NO_HZ.txt"
* 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
sched: Keep at least 1 tick per second for active dynticks tasks
rcu: Fix full dynticks' dependency on wide RCU nocb mode
nohz: Protect smp_processor_id() in tick_nohz_task_switch()
nohz_full: Add documentation.
cputime_nsecs: use math64.h for nsec resolution conversion helpers
nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config
nohz: Reduce overhead under high-freq idling patterns
nohz: Remove full dynticks' superfluous dependency on RCU tree
nohz: Fix unavailable tick_stop tracepoint in dynticks idle
nohz: Add basic tracing
nohz: Select wide RCU nocb for full dynticks
nohz: Disable the tick when irq resume in full dynticks CPU
nohz: Re-evaluate the tick for the new task after a context switch
nohz: Prepare to stop the tick on irq exit
nohz: Implement full dynticks kick
nohz: Re-evaluate the tick from the scheduler IPI
sched: New helper to prevent from stopping the tick in full dynticks
sched: Kick full dynticks CPU that have more than one task enqueued.
perf: New helper to prevent full dynticks CPUs from stopping tick
perf: Kick full dynticks CPU if events rotation is needed
...
Future AMD processors, starting with Family 16h, can provide software
with feedback on how the workload may respond to frequency change --
memory-bound workloads will not benefit from higher frequency, where
as compute-bound workloads will. This patch enables this "frequency
sensitivity feedback" to aid the ondemand governor to make better
frequency change decisions by hooking into the powersave bias.
Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
We are planning to convert the dynticks Kconfig options layout
into a choice menu. The user must be able to easily pick
any of the following implementations: constant periodic tick,
idle dynticks, full dynticks.
As this implies a mutual exclusion, the two dynticks implementions
need to converge on the selection of a common Kconfig option in order
to ease the sharing of a common infrastructure.
It would thus seem pretty natural to reuse CONFIG_NO_HZ to
that end. It already implements all the idle dynticks code
and the full dynticks depends on all that code for now.
So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and
CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ.
On the other hand we want to stay backward compatible: if
CONFIG_NO_HZ is set in an older config file, we want to
enable CONFIG_NO_HZ_IDLE by default.
But we can't afford both at the same time or we run into
a circular dependency:
1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select
CONFIG_NO_HZ
2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE
We might be able to support that from Kconfig/Kbuild but it
may not be wise to introduce such a confusing behaviour.
So to solve this, create a new CONFIG_NO_HZ_COMMON option
which gathers the common code between idle and full dynticks
(that common code for now is simply the idle dynticks code)
and select it from their referring Kconfig.
Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ
to it for backward compatibility.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Some assignments of policy-> min/max/cur/cpuinfo.min_freq/cpuinfo.max_freq
aren't required as part of it is done by cpufreq driver or cpufreq core.
Remove them.
At some places we merge multiple lines together too.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
At few places in documentation cpufreq_frequency_table is written as
cpufreq_freq_table. Fix these.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
sampling_down_factor tunable is unused since commit
8e677ce83b (4 years ago).
This patch restores the original functionality and documents the
tunable.
Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Documentation related to cpus and related_cpus is confusing and not very clear.
Over that CPUFreq core has seen much changes recently. Lets update documentation
and comments for cpus and related_cpus.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
One feature present in powernow-k8 that isn't present in acpi-cpufreq
is support for enabling or disabling AMD's core performance boost
technology. This patch adds support to acpi-cpufreq, but also
includes support for Intel's dynamic acceleration.
The original boost disabling sysfs file was per CPU, but acted
globally. Also the naming (cpb) was at least not intuitive.
So lets introduce a single file simply called "boost", which sits
once in /sys/devices/system/cpu/cpufreq.
This should be the only way of using this feature, so add
documentation about the rationale and the usage.
A following patch will re-introduce the cpb knob for compatibility
reasons on AMD CPUs.
Per-CPU boost switching is possible, but not trivial and is thus
postponed to a later patch series.
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
'sampling_rate_max' was removed with commit ef598549 ("[...] Remove
deprecated sysfs file sampling_rate_max"), so its line can be dropped
from governors.txt. And 'show_sampling_rate_min' is a typo: the sysfs
file is called 'sampling_rate_min'.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Change all "arch/i386" to "arch/x86" in Documentaion/,
since the directory has changed.
Also update the files which have changed their filename
in the meantime accordingly.
Signed-off-by: Wanlong Gao <wanlong.gao@gmail.com>
[jkosina@suse.cz: reword changelog]
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Processor Clocking Control (PCC) is an interface between the BIOS and OSPM.
Based on the server workload, OSPM can request what frequency it expects
from a logical CPU, and the BIOS will achieve that frequency transparently.
This patch introduces driver support for PCC. OSPM uses the PCC driver to
communicate with the BIOS via the PCC interface.
There is a Documentation file that provides a link to the PCC
Specification, and also provides a summary of the PCC interface.
Currently, certain HP ProLiant platforms implement the PCC interface. However,
any platform whose BIOS implements the PCC Specification, can utilize this
driver.
V2 --> V1 changes (based on Dominik's suggestions):
- Removed the dependency on CPU_FREQ_TABLE
- "cpufreq_stats" will no longer PANIC. Actually, it will not load anymore
because it is not applicable.
- Removed the sanity check for target frequency in the ->target routine.
NOTE: A patch to sanitize the target frequency requested by "ondemand" is
needed to ensure that the target freq < policy->min.
Can this driver be queued up for the 2.6.33 tree?
Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
This interface is mainly intended (and implemented) for ACPI _PPC BIOS
frequency limitations, but other cpufreq drivers can also use it for
similar use-cases.
Why is this needed:
Currently it's not obvious why cpufreq got limited.
People see cpufreq/scaling_max_freq reduced, but this could have
happened by:
- any userspace prog writing to scaling_max_freq
- thermal limitations
- hardware (_PPC in ACPI case) limitiations
Therefore export bios_limit (in kHz) to:
- Point the user that it's the BIOS (broken or intended) which limits
frequency
- Export it as a sysfs interface for userspace progs.
While this was a rarely used feature on laptops, there will appear
more and more server implemenations providing "Green IT" features like
allowing the service processor to limit the frequency. People want
to know about HW/BIOS frequency limitations.
All ACPI P-state driven cpufreq drivers are covered with this patch:
- powernow-k8
- powernow-k7
- acpi-cpufreq
Tested with a patched DSDT which limits the first two cores (_PPC returns 1)
via _PPC, exposed by bios_limit:
# echo 2200000 >cpu2/cpufreq/scaling_max_freq
# cat cpu*/cpufreq/scaling_max_freq
2600000
2600000
2200000
2200000
# #scaling_max_freq shows general user/thermal/BIOS limitations
# cat cpu*/cpufreq/bios_limit
2600000
2600000
2800000
2800000
# #bios_limit only shows the HW/BIOS limitation
CC: Pallipadi Venkatesh <venkatesh.pallipadi@intel.com>
CC: Len Brown <lenb@kernel.org>
CC: davej@codemonkey.org.uk
CC: linux@dominikbrodowski.net
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
They're documented in the header but not in Documentation.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dave Jones <davej@redhat.com>
I think the way "cpuinfo_cur_info" and "scaling_cur_info" are defined under
./Documentation/cpu-freq/user-guide.txt can be enhanced. Currently, they are
both defined the same way: "Current speed/frequency" of the CPU, in KHz".
Below is a patch that distinguishes one from the other.
Regards,
- naga -
-----------------------------------------
Update description for "cpuinfo_cur_freq" and "scaling_cur_freq".
Some of the wording is drawn from comments found in
./drivers/cpufreq/cpufreq.c: cpufreq_out_of_sync():
* @old_freq: CPU frequency the kernel thinks the CPU runs at
* @new_freq: CPU frequency the CPU actually runs at
Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Dave Jones <davej@redhat.com>
I have been reading the documentation for cpufreq closely. Found a couple of
minor errors in the Documentation.
Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Update the documentation accordingly.
Cleanup and use printk_once.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
Limit sampling rate to transition_latency * 100 or kernel limits.
If sampling_rate is tried to be set too low, set the lowest allowed value.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
The same info can be obtained via the transition_latency sysfs file
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
It's not only useful for the ondemand and conservative governors, but
also for userspace daemons to know about the HW transition latency of
the CPU.
It is especially useful for userspace to know about this value when
the ondemand or conservative governors are run. The sampling rate
control value depends on it and for userspace being able to set sane
tuning values there it has to know about the transition latency.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
They were long enough set deprecated...
Update Documentation/cpu-freq/users-guide.txt:
The deprecated files listed there seen not to exist for some time anymore
already.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>
The sh cpufreq driver is no longer limited to just the SH-3 and SH-4,
update the documentation to reflect this fact accordingly.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Replace the no longer working links and email address in the
documentation and in source code.
Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Dave Jones <davej@redhat.com>
There is a description of some of the sysfs files. However, there are some
that are not mentioned in the documentation, so add them to the user's guide.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>
There have been patches hanging around for ages to add support for
cpufreq to PXA255 processors. It's about time we applied one.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Fix various typos in kernel docs and Kconfigs, 2.6.21-rc4.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
This patch fixes typos in various Documentation txts. The patch addresses some
misc words.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Fix reference to where the code actually is. Noted by Hero Wanders.
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Dave Jones <davej@redhat.com>
This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letter 'S'.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Alan Cox <alan@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letters 'N'-'P'.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letters 'H'-'M'.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letters 'F'-'G'.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
I just stumbled on this bug/feature, this is how to reproduce it:
# echo 450000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
# echo 450000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
# echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
# cpufreq-info -p
450000 450000 powersave
# echo 1800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq ; echo $?
0
# cpufreq-info -p
450000 450000 powersave
Here it is. The kernel refuses to set a min_freq higher than the
max_freq but it allows a max_freq lower than min_freq (lowering min_freq
also).
This behaviour is pretty straightforward (but undocumented) and it
doesn't return an error altough failing to accomplish the requested
action (set min_freq).
The problem (IMO) is basically that userspace is not allowed to set a
full policy atomically while the kernel always does that thus it must
enforce an ordering on operations.
The attached patch returns -EINVAL if trying to increase frequencies
starting from scaling_min_freq and documents the correct ordering of writes.
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Dominik Brodowski <linux at dominikbrodowski.net>
Signed-off-by: Dave Jones <davej@redhat.com>
--
Viresh Kumar