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[CPUFREQ] Disable sysfs ui for p4-clockmod.

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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>
This commit is contained in:
Matthew Garrett 2008-11-25 13:29:47 -05:00 committed by Dave Jones
parent 10db2e5cbd
commit e088e4c9cd
3 changed files with 36 additions and 19 deletions
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1
arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
View file

@ -276,6 +276,7 @@ static struct cpufreq_driver p4clockmod_driver = {
.name = "p4-clockmod",
.owner = THIS_MODULE,
.attr = p4clockmod_attr,
.hide_interface = 1,
};

53
drivers/cpufreq/cpufreq.c
View file

@ -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;
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;
/* 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);
/* 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;
}

1
include/linux/cpufreq.h
View file

@ -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 */