[CPUFREQ] Disable sysfs ui for p4-clockmod.
commite088e4c9cdb618675874becb91b2fd581ee707e6
authorMatthew Garrett <mjg@redhat.com>
Tue, 25 Nov 2008 18:29:47 +0000 (25 13:29 -0500)
committerDave Jones <davej@redhat.com>
Fri, 5 Dec 2008 20:20:10 +0000 (5 15:20 -0500)
tree48231c406061308502f13c7781a6957ef396a739
parent10db2e5cbda5b4e13d2e2f134b963bee2e129999
[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>
arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
drivers/cpufreq/cpufreq.c
include/linux/cpufreq.h