Commit Graph

121 Commits

Author SHA1 Message Date
Ingo Molnar
6e15cf0486 Merge branch 'core/percpu' into percpu-cpumask-x86-for-linus-2
Conflicts:
	arch/parisc/kernel/irq.c
	arch/x86/include/asm/fixmap_64.h
	arch/x86/include/asm/setup.h
	kernel/irq/handle.c

Semantic merge:
        arch/x86/include/asm/fixmap.h

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-27 17:28:43 +01:00
Linus Torvalds
ada19a31a9 Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq: (35 commits)
  [CPUFREQ] Prevent p4-clockmod from auto-binding to the ondemand governor.
  [CPUFREQ] Make cpufreq-nforce2 less obnoxious
  [CPUFREQ] p4-clockmod reports wrong frequency.
  [CPUFREQ] powernow-k8: Use a common exit path.
  [CPUFREQ] Change link order of x86 cpufreq modules
  [CPUFREQ] conservative: remove 10x from def_sampling_rate
  [CPUFREQ] conservative: fixup governor to function more like ondemand logic
  [CPUFREQ] conservative: fix dbs_cpufreq_notifier so freq is not locked
  [CPUFREQ] conservative: amend author's email address
  [CPUFREQ] Use swap() in longhaul.c
  [CPUFREQ] checkpatch cleanups for acpi-cpufreq
  [CPUFREQ] powernow-k8: Only print error message once, not per core.
  [CPUFREQ] ondemand/conservative: sanitize sampling_rate restrictions
  [CPUFREQ] ondemand/conservative: deprecate sampling_rate{min,max}
  [CPUFREQ] powernow-k8: Always compile powernow-k8 driver with ACPI support
  [CPUFREQ] Introduce /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_transition_latency
  [CPUFREQ] checkpatch cleanups for powernow-k8
  [CPUFREQ] checkpatch cleanups for ondemand governor.
  [CPUFREQ] checkpatch cleanups for powernow-k7
  [CPUFREQ] checkpatch cleanups for speedstep related drivers.
  ...
2009-03-26 11:04:08 -07:00
Dave Jones
129f8ae9b1 Revert "[CPUFREQ] Disable sysfs ui for p4-clockmod."
This reverts commit e088e4c9cd.

Removing the sysfs interface for p4-clockmod was flagged as a
regression in bug 12826.

Course of action:
 - Find out the remaining causes of overheating, and fix them
   if possible. ACPI should be doing the right thing automatically.
   If it isn't, we need to fix that.
 - mark p4-clockmod ui as deprecated
 - try again with the removal in six months.

It's not really feasible to printk about the deprecation, because
it needs to happen at all the sysfs entry points, which means adding
a lot of strcmp("p4-clockmod".. calls to the core, which.. bleuch.

Signed-off-by: Dave Jones <davej@redhat.com>
2009-03-09 15:07:33 -04:00
Dave Jones
36e8abf3ed [CPUFREQ] Prevent p4-clockmod from auto-binding to the ondemand governor.
The latency of p4-clockmod sucks so hard that scaling on a regular
basis with ondemand is a really bad idea.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-03-05 00:16:26 -05:00
Matthew Garrett
eb3092cee7 [CPUFREQ] Make cpufreq-nforce2 less obnoxious
Not owning an nforce2 is a sign of good taste, not an error.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:32 -05:00
Matthias-Christian Ott
199785eac8 [CPUFREQ] p4-clockmod reports wrong frequency.
http://bugzilla.kernel.org/show_bug.cgi?id=10968

[ Updated for current tree, and fixed compile failure
  when p4-clockmod was built modular -- davej]

From: Matthias-Christian Ott <ott@mirix.org>
Signed-off-by: Dominik Brodowski <linux@brodo.de>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:32 -05:00
Dave Jones
0cb8bc2560 [CPUFREQ] powernow-k8: Use a common exit path.
a0abd520fd introduced a slew of
extra kfree/return -ENODEV pairs. This replaces them all
with gotos.

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:32 -05:00
Matthew Garrett
de3ed81d74 [CPUFREQ] Change link order of x86 cpufreq modules
Change the link order of the cpufreq modules to ensure that they're
probed in the preferred order when statically linked in.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:32 -05:00
Dave Jones
91420220d2 [CPUFREQ] Use swap() in longhaul.c
Remove hand-coded implementation of swap()

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:31 -05:00
Dave Jones
3a58df35a6 [CPUFREQ] checkpatch cleanups for acpi-cpufreq
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:31 -05:00
Thomas Renninger
79cc56af9f [CPUFREQ] powernow-k8: Only print error message once, not per core.
This is the typical message you get if you plug in a CPU
which is newer than your BIOS. It's annoying seeing this
message for each core.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:31 -05:00
Thomas Renninger
57f4fa6991 [CPUFREQ] powernow-k8: Always compile powernow-k8 driver with ACPI support
powernow-k8 driver should always try to get cpufreq info from ACPI.
Otherwise it will not be able to detect the transition latency correctly
which results in ondemand governor taking a wrong sampling rate which will
then result in sever performance loss.

Let the user not shoot himself in the foot and always compile in ACPI
support for powernow-k8.

This also fixes a wrong message if ACPI_PROCESSOR is compiled as a module and
#ifndef CONFIG_ACPI_PROCESSOR
path is chosen.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:31 -05:00
Dave Jones
0e64a0c982 [CPUFREQ] checkpatch cleanups for powernow-k8
This driver has so many long function names, and deep nested if's
The remaining warnings will need some code restructuring to clean up.

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:30 -05:00
Dave Jones
b9e7638a30 [CPUFREQ] checkpatch cleanups for powernow-k7
The asm/timer.h warning can be ignored, it's needed for
recalibrate_cpu_khz()

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:30 -05:00
Dave Jones
bbfebd6655 [CPUFREQ] checkpatch cleanups for speedstep related drivers.
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:30 -05:00
Dave Jones
6072ace436 [CPUFREQ] checkpatch cleanups for sc520
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:29 -05:00
Dave Jones
14a6650f13 [CPUFREQ] checkpatch cleanups for powernow-k6
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:29 -05:00
Dave Jones
48ee923a66 [CPUFREQ] checkpatch cleanups for longrun
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:29 -05:00
Dave Jones
ac617bd0f7 [CPUFREQ] checkpatch cleanups for longhaul
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:29 -05:00
Dave Jones
00f6a235bf [CPUFREQ] checkpatch cleanups for gx-suspmod
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:29 -05:00
Dave Jones
c9b8c87152 [CPUFREQ] checkpatch cleanups for e_powersaver
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:28 -05:00
Dave Jones
04cd1a99dc [CPUFREQ] checkpatch cleanups for elanfreq
The remaining warning about the simple_strtoul conversion
to strict_strtoul seems kind of pointless to me.

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:28 -05:00
Dave Jones
20174b65d9 [CPUFREQ] nforce2: Use driver prefix, not cpufreq prefix.
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:28 -05:00
Dave Jones
b5c9166662 [CPUFREQ] checkpatch cleanups for cpufreq-nforce2
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:28 -05:00
Dave Jones
fff78ad5ce [CPUFREQ] Stupidly trivial CodingStyle fix
GNU indent complains about this being ambiguous, because it's dumb.
One of my automated tests relies on the output of indent, so this shuts
it up.

Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-24 22:47:28 -05:00
Ingo Molnar
0edcf8d692 Merge branch 'tj-percpu' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into core/percpu
Conflicts:
	arch/x86/include/asm/pgtable.h
2009-02-24 21:52:45 +01:00
Ingo Molnar
609162850d Merge branches 'x86/asm', 'x86/cleanups' and 'x86/headers' into x86/core 2009-02-20 17:40:50 +01:00
Vegard Nossum
ecab22aa6d x86: use symbolic constants for MSR_IA32_MISC_ENABLE bits
Impact: Cleanup. No functional changes.

Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-20 12:07:43 +01:00
Rusty Russell
b36128c830 alloc_percpu: change percpu_ptr to per_cpu_ptr
Impact: cleanup

There are two allocated per-cpu accessor macros with almost identical
spelling.  The original and far more popular is per_cpu_ptr (44
files), so change over the other 4 files.

tj: kill percpu_ptr() and update UP too

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: mingo@redhat.com
Cc: lenb@kernel.org
Cc: cpufreq@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-02-20 16:29:08 +09:00
Rusty Russell
a0abd520fd cpumask: fix powernow-k8: partial revert of 2fdf66b491
Impact: fix powernow-k8 when acpi=off (or other error).

There was a spurious change introduced into powernow-k8 in this patch:
so that we try to "restore" the cpus_allowed we never saved.  We revert
that file.

See lkml "[PATCH] x86/powernow: fix cpus_allowed brokage when
acpi=off" from Yinghai for the bug report.

Cc: Mike Travis <travis@sgi.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
2009-02-16 17:31:59 +10:30
Linus Torvalds
6707fbb56c Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
  [CPUFREQ] powernow-k8: Get transition latency from ACPI _PSS table
  [CPUFREQ] Make ignore_nice_load setting of ondemand work as expected.
2009-02-09 13:58:22 -08:00
Mark Langsdorf
732553e567 [CPUFREQ] powernow-k8: Get transition latency from ACPI _PSS table
At this time, the PowerNow! driver for K8 uses an experimentally
derived formula to calculate transition latency.  The value it
provides is orders of magnitude too large on modern systems.
This patch replaces the formula with ACPI _PSS latency values
for more accuracy and better performance.

I've tested it on two 2nd generation Opteron systems, a 3rd
generation Operton system, and a Turion X2 without seeing any
stability problems.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
2009-02-05 12:25:26 -05:00
Thomas Renninger
62663ea822 ACPI: cpufreq: Remove deprecated /proc/acpi/processor/../performance proc entries
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>
2009-02-04 00:12:24 -05:00
Ingo Molnar
bfa318ad52 fix: crash: IP: __bitmap_intersects+0x48/0x73
-tip testing found this crash:

> [   35.258515] calling  acpi_cpufreq_init+0x0/0x127 @ 1
> [   35.264127] BUG: unable to handle kernel NULL pointer dereference at (null)
> [   35.267554] IP: [<ffffffff80478092>] __bitmap_intersects+0x48/0x73
> [   35.267554] PGD 0
> [   35.267554] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC

arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c is still broken: there's no
allocation of the variable mask, so we pass in an uninitialized cmd.mask
field to drv_read(), which then passes it to the scheduler which then
crashes ...

Switch it over to the much simpler constant-cpumask-pointers approach.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-20 00:17:01 +01:00
Mike Travis
7285908185 cpufreq: use work_on_cpu in acpi-cpufreq.c for drv_read and drv_write
Impact: use new work_on_cpu function to reduce stack usage

Replace the saving of current->cpus_allowed and set_cpus_allowed_ptr() with
a work_on_cpu function for drv_read() and drv_write().

Basically converts do_drv_{read,write} into "work_on_cpu" functions that
are now called by drv_read and drv_write.

Note: This patch basically reverts 50c668d6 which reverted 7503bfba, now
that the work_on_cpu() function is more stable.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Dieter Ries <clip2@gmx.de>
Tested-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Cc: Dave Jones <davej@redhat.com>
Cc: <cpufreq@vger.kernel.org>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-19 22:36:13 +01:00
Ingo Molnar
4a922a969c x86, cpufreq: remove leftover copymask_copy()
Impact: fix potential boot crash on MAXSMP

Remove code left over by:

  50c668d: Revert "cpumask: use work_on_cpu in acpi-cpufreq.c for drv_read

That cmd.cpumask is not allocated anymore. No impact on default !MAXSMP
kernels.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-13 16:11:00 +01:00
Ingo Molnar
50c668d678 Revert "cpumask: use work_on_cpu in acpi-cpufreq.c for drv_read and drv_write"
This reverts commit 7503bfbae8.

Dieter Ries reported bootup soft-hangs and bisected it back to
this commit, and reverting this commit gave him a working system.

The commit introduces work_on_cpu() use into the cpufreq code,
but that is subtly problematic from a lock hierarchy POV: the
hotplug-cpu lock is an highlevel lock that is taken before
lowlevel locks, and in this codepath we are called with the
policy lock taken.

Dieter did not have lockdep enabled so we dont have a nice stack
trace proof for this, but using work_on_cpu() in such a lowlevel
place certainly looks wrong, so we revert the patch.

work_on_cpu() needs to be reworked to be more generally usable.

Reported-by: Dieter Ries <clip2@gmx.de>
Tested-by: Dieter Ries <clip2@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-12 19:24:23 +01:00
Linus Torvalds
4e9b1c184c Merge branch 'cpus4096-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'cpus4096-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  [IA64] fix typo in cpumask_of_pcibus()
  x86: fix x86_32 builds for summit and es7000 arch's
  cpumask: use work_on_cpu in acpi-cpufreq.c for read_measured_perf_ctrs
  cpumask: use work_on_cpu in acpi-cpufreq.c for drv_read and drv_write
  cpumask: use cpumask_var_t in acpi-cpufreq.c
  cpumask: use work_on_cpu in acpi/cstate.c
  cpumask: convert struct cpufreq_policy to cpumask_var_t
  cpumask: replace CPUMASK_ALLOC etc with cpumask_var_t
  x86: cleanup remaining cpumask_t ops in smpboot code
  cpumask: update pci_bus_show_cpuaffinity to use new cpumask API
  cpumask: update local_cpus_show to use new cpumask API
  ia64: cpumask fix for is_affinity_mask_valid()
2009-01-10 06:12:18 -08:00
Fernando Carrijo
c19a28e119 remove lots of double-semicolons
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: James Morris <jmorris@namei.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-08 08:31:14 -08:00
Mike Travis
e39ad415ac cpumask: use work_on_cpu in acpi-cpufreq.c for read_measured_perf_ctrs
Impact: use new cpumask API to reduce stack usage

Replace the saving of current->cpus_allowed and set_cpus_allowed_ptr() with
a work_on_cpu function for read_measured_perf_ctrs().

Basically splits off the work function from get_measured_perf which is
run on the designated cpu.  Moves definition of struct perf_cur out of
function local namespace, and is used as the work function argument.
References in get_measured_perf use values in the perf_cur struct.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-06 09:05:43 +01:00
Mike Travis
7503bfbae8 cpumask: use work_on_cpu in acpi-cpufreq.c for drv_read and drv_write
Impact: use new cpumask API to reduce stack usage

Replace the saving of current->cpus_allowed and set_cpus_allowed_ptr() with
a work_on_cpu function for drv_read() and drv_write().

Basically converts do_drv_{read,write} into "work_on_cpu" functions that
are now called by drv_read and drv_write.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-06 09:05:40 +01:00
Mike Travis
4d8bb53749 cpumask: use cpumask_var_t in acpi-cpufreq.c
Impact: cleanup, reduce stack usage, use new cpumask API.

Replace the cpumask_t in struct drv_cmd with a cpumask_var_t.  Remove unneeded
online_policy_cpus cpumask_t in acpi_cpufreq_target.  Update refs to use
new cpumask API.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-06 09:05:37 +01:00
Rusty Russell
835481d9bc cpumask: convert struct cpufreq_policy to cpumask_var_t
Impact: use new cpumask API to reduce memory usage

This is part of an effort to reduce structure sizes for machines
configured with large NR_CPUS.  cpumask_t gets replaced by
cpumask_var_t, which is either struct cpumask[1] (small NR_CPUS) or
struct cpumask * (large NR_CPUS).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Dave Jones <davej@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-06 09:05:31 +01:00
Rusty Russell
5cb0535f17 cpumask: replace CPUMASK_ALLOC etc with cpumask_var_t
Impact: cleanup

There's only one user, and it's a fairly easy conversion.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Dave Jones <davej@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-06 09:05:28 +01:00
Linus Torvalds
e9af797d75 Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq:
  [CPUFREQ] Fix on resume, now preserves user policy min/max.
  [CPUFREQ] Add Celeron Core support to p4-clockmod.
  [CPUFREQ] add to speedstep-lib additional fsb values for core processors
  [CPUFREQ] Disable sysfs ui for p4-clockmod.
  [CPUFREQ] p4-clockmod: reduce noise
  [CPUFREQ] clean up speedstep-centrino and reduce cpumask_t usage
2009-01-05 18:33:38 -08:00
Mike Travis
80855f7361 cpumask: use alloc_cpumask_var_node where appropriate
Impact: Reduce inter-node memory traffic.

Reduces inter-node memory traffic (offloading the global system bus)
by allocating referenced struct cpumasks on the same node as the
referring struct.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-03 19:15:40 +01:00
Rusty Russell
2fdf66b491 cpumask: convert shared_cpu_map in acpi_processor* structs to cpumask_var_t
Impact: Reduce memory usage, use new API.

This is part of an effort to reduce structure sizes for machines
configured with large NR_CPUS.  cpumask_t gets replaced by
cpumask_var_t, which is either struct cpumask[1] (small NR_CPUS) or
struct cpumask * (large NR_CPUS).

(Changes to powernow-k* by <travis>.)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-03 19:15:40 +01:00
Herton Ronaldo Krzesinski
8529154ec3 [CPUFREQ] Add Celeron Core support to p4-clockmod.
Add Celeron Core support to p4-clockmod.

Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Signed-off-by: Dave Jones <davej@redhat.com>
2008-12-05 15:20:11 -05:00
Herton Ronaldo Krzesinski
c60e19eb21 [CPUFREQ] add to speedstep-lib additional fsb values for core processors
Add additional fsb values to pentium_core_get_frequency, from latest edition
(September 2008) of Intel 64 and IA-32 Architectures Software Develper's Manual,
Volume 3B: System Programming Guide, Part 2. Values added are to detect 800,
1067 and 1333 FSB types.

Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Signed-off-by: Dave Jones <davej@redhat.com>
2008-12-05 15:20:11 -05:00
Matthew Garrett
e088e4c9cd [CPUFREQ] Disable sysfs ui for p4-clockmod.
p4-clockmod has a long history of abuse.   It pretends to be a CPU
frequency scaling driver, even though it doesn't actually change
the CPU frequency, but instead just modulates the frequency with
wait-states.
The biggest misconception is that when running at the lower 'frequency'
p4-clockmod is saving power.  This isn't the case, as workloads running
slower take longer to complete, preventing the CPU from entering deep C states.

However p4-clockmod does have a purpose.  It can prevent overheating.
Having it hooked up to the cpufreq interfaces is the wrong way to achieve
cooling however. It should instead be hooked up to ACPI.

This diff introduces a means for a cpufreq driver to register with the
cpufreq core, but not present a sysfs interface.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Dave Jones <davej@redhat.com>
2008-12-05 15:20:10 -05:00