[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>

diff --git a/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c b/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
index ba3a94a..0c43b22 100644 (file)
--- 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 31d6f53..9044b91 100644 (file)
--- 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 1ee608f..484b3ab 100644 (file)
--- 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 */