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Commit e088e4c9 authored by Matthew Garrett's avatar Matthew Garrett Committed by Dave Jones
Browse files

[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: default avatarMatthew Garrett <mjg@redhat.com>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 10db2e5c

arch/x86/kernel/cpu/cpufreq/p4-clockmod.c

+1 −0
Original line number Diff line number Diff line
@@ -276,6 +276,7 @@ static struct cpufreq_driver p4clockmod_driver = { 
	.name		= "p4-clockmod",

	.owner		= THIS_MODULE,

	.attr		= p4clockmod_attr,

	.hide_interface	= 1,

};

drivers/cpufreq/cpufreq.c

+33 −18
Original line number Diff line number Diff line
@@ -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 (!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));

			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);

			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);

			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;

	}

include/linux/cpufreq.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */