From e088e4c9cdb618675874becb91b2fd581ee707e6 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg@redhat.com>
Date: Tue, 25 Nov 2008 13:29:47 -0500
Subject: [PATCH] [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 | 1 +
drivers/cpufreq/cpufreq.c | 51 +++++++++++++++--------
include/linux/cpufreq.h | 1 +
3 files changed, 35 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c b/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
index ba3a94a997c3..0c43b2240517 100644
--- a/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
+++ b/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
@@ -276,6 +276,7 @@ static struct cpufreq_driver p4clockmod_driver = {
.name = "p4-clockmod",
.owner = THIS_MODULE,
.attr = p4clockmod_attr,
+ .hide_interface = 1,
};
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 31d6f535a79d..9044b911d8ae 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -754,6 +754,11 @@ static struct kobj_type ktype_cpufreq = {
.release = cpufreq_sysfs_release,
};
+static struct kobj_type ktype_empty_cpufreq = {
+ .sysfs_ops = &sysfs_ops,
+ .release = cpufreq_sysfs_release,
+};
+
/**
* cpufreq_add_dev - add a CPU device
@@ -876,26 +881,36 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
memcpy(&new_policy, policy, sizeof(struct cpufreq_policy));
/* prepare interface data */
- ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq, &sys_dev->kobj,
- "cpufreq");
- if (ret)
- goto err_out_driver_exit;
-
- /* set up files for this cpu device */
- drv_attr = cpufreq_driver->attr;
- while ((drv_attr) && (*drv_attr)) {
- ret = sysfs_create_file(&policy->kobj, &((*drv_attr)->attr));
+ if (!cpufreq_driver->hide_interface) {
+ ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
+ &sys_dev->kobj, "cpufreq");
if (ret)
goto err_out_driver_exit;
- drv_attr++;
- }
- if (cpufreq_driver->get) {
- ret = sysfs_create_file(&policy->kobj, &cpuinfo_cur_freq.attr);
- if (ret)
- goto err_out_driver_exit;
- }
- if (cpufreq_driver->target) {
- ret = sysfs_create_file(&policy->kobj, &scaling_cur_freq.attr);
+
+ /* set up files for this cpu device */
+ drv_attr = cpufreq_driver->attr;
+ while ((drv_attr) && (*drv_attr)) {
+ ret = sysfs_create_file(&policy->kobj,
+ &((*drv_attr)->attr));
+ if (ret)
+ goto err_out_driver_exit;
+ drv_attr++;
+ }
+ if (cpufreq_driver->get) {
+ ret = sysfs_create_file(&policy->kobj,
+ &cpuinfo_cur_freq.attr);
+ if (ret)
+ goto err_out_driver_exit;
+ }
+ if (cpufreq_driver->target) {
+ ret = sysfs_create_file(&policy->kobj,
+ &scaling_cur_freq.attr);
+ if (ret)
+ goto err_out_driver_exit;
+ }
+ } else {
+ ret = kobject_init_and_add(&policy->kobj, &ktype_empty_cpufreq,
+ &sys_dev->kobj, "cpufreq");
if (ret)
goto err_out_driver_exit;
}
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 1ee608fd7b77..484b3abf61bb 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -234,6 +234,7 @@ struct cpufreq_driver {
int (*suspend) (struct cpufreq_policy *policy, pm_message_t pmsg);
int (*resume) (struct cpufreq_policy *policy);
struct freq_attr **attr;
+ bool hide_interface;
};
/* flags */
--
2.39.5