Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -541,7 +541,6 @@ static void intel_pstate_exit_perf_limit
 
 	acpi_processor_unregister_performance(policy->cpu);
 }
-
 #else
 static inline void intel_pstate_init_acpi_perf_limits(struct cpufreq_policy *policy)
 {
@@ -1010,35 +1009,57 @@ static int pid_param_get(void *data, u64
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_pid_param, pid_param_get, pid_param_set, "%llu\n");
 
+static struct dentry *debugfs_parent;
+
 struct pid_param {
 	char *name;
 	void *value;
+	struct dentry *dentry;
 };
 
 static struct pid_param pid_files[] = {
-	{"sample_rate_ms", &pid_params.sample_rate_ms},
-	{"d_gain_pct", &pid_params.d_gain_pct},
-	{"i_gain_pct", &pid_params.i_gain_pct},
-	{"deadband", &pid_params.deadband},
-	{"setpoint", &pid_params.setpoint},
-	{"p_gain_pct", &pid_params.p_gain_pct},
-	{NULL, NULL}
+	{"sample_rate_ms", &pid_params.sample_rate_ms, },
+	{"d_gain_pct", &pid_params.d_gain_pct, },
+	{"i_gain_pct", &pid_params.i_gain_pct, },
+	{"deadband", &pid_params.deadband, },
+	{"setpoint", &pid_params.setpoint, },
+	{"p_gain_pct", &pid_params.p_gain_pct, },
+	{NULL, NULL, }
 };
 
-static void __init intel_pstate_debug_expose_params(void)
+static void intel_pstate_debug_expose_params(void)
 {
-	struct dentry *debugfs_parent;
-	int i = 0;
+	int i;
 
 	debugfs_parent = debugfs_create_dir("pstate_snb", NULL);
 	if (IS_ERR_OR_NULL(debugfs_parent))
 		return;
-	while (pid_files[i].name) {
-		debugfs_create_file(pid_files[i].name, 0660,
-				    debugfs_parent, pid_files[i].value,
-				    &fops_pid_param);
-		i++;
+
+	for (i = 0; pid_files[i].name; i++) {
+		struct dentry *dentry;
+
+		dentry = debugfs_create_file(pid_files[i].name, 0660,
+					     debugfs_parent, pid_files[i].value,
+					     &fops_pid_param);
+		if (!IS_ERR(dentry))
+			pid_files[i].dentry = dentry;
+	}
+}
+
+static void intel_pstate_debug_hide_params(void)
+{
+	int i;
+
+	if (IS_ERR_OR_NULL(debugfs_parent))
+		return;
+
+	for (i = 0; pid_files[i].name; i++) {
+		debugfs_remove(pid_files[i].dentry);
+		pid_files[i].dentry = NULL;
 	}
+
+	debugfs_remove(debugfs_parent);
+	debugfs_parent = NULL;
 }
 
 /************************** debugfs end ************************/
@@ -1051,6 +1072,34 @@ static void __init intel_pstate_debug_ex
 		return sprintf(buf, "%u\n", limits->object);		\
 	}
 
+static ssize_t intel_pstate_show_status(char *buf);
+static int intel_pstate_update_status(const char *buf, size_t size);
+
+static ssize_t show_status(struct kobject *kobj,
+			   struct attribute *attr, char *buf)
+{
+	ssize_t ret;
+
+	mutex_lock(&intel_pstate_driver_lock);
+	ret = intel_pstate_show_status(buf);
+	mutex_unlock(&intel_pstate_driver_lock);
+
+	return ret;
+}
+
+static ssize_t store_status(struct kobject *a, struct attribute *b,
+			    const char *buf, size_t count)
+{
+	char *p = memchr(buf, '\n', count);
+	int ret;
+
+	mutex_lock(&intel_pstate_driver_lock);
+	ret = intel_pstate_update_status(buf, p ? p - buf : count);
+	mutex_unlock(&intel_pstate_driver_lock);
+
+	return ret < 0 ? ret : count;
+}
+
 static ssize_t show_turbo_pct(struct kobject *kobj,
 				struct attribute *attr, char *buf)
 {
@@ -1235,6 +1284,7 @@ static ssize_t store_min_perf_pct(struct
 show_one(max_perf_pct, max_perf_pct);
 show_one(min_perf_pct, min_perf_pct);
 
+define_one_global_rw(status);
 define_one_global_rw(no_turbo);
 define_one_global_rw(max_perf_pct);
 define_one_global_rw(min_perf_pct);
@@ -1242,6 +1292,7 @@ define_one_global_ro(turbo_pct);
 define_one_global_ro(num_pstates);
 
 static struct attribute *intel_pstate_attributes[] = {
+	&status.attr,
 	&no_turbo.attr,
 	&turbo_pct.attr,
 	&num_pstates.attr,
@@ -2316,6 +2367,111 @@ static struct cpufreq_driver intel_cpufr
 
 static struct cpufreq_driver *intel_pstate_driver = &intel_pstate;
 
+static void intel_pstate_driver_cleanup(void)
+{
+	unsigned int cpu;
+
+	get_online_cpus();
+	for_each_online_cpu(cpu) {
+		if (all_cpu_data[cpu]) {
+			if (intel_pstate_driver == &intel_pstate)
+				intel_pstate_clear_update_util_hook(cpu);
+
+			kfree(all_cpu_data[cpu]);
+			all_cpu_data[cpu] = NULL;
+		}
+	}
+	put_online_cpus();
+}
+
+static int intel_pstate_register_driver(void)
+{
+	int ret;
+
+	ret = cpufreq_register_driver(intel_pstate_driver);
+	if (ret) {
+		intel_pstate_driver_cleanup();
+		return ret;
+	}
+
+	mutex_lock(&intel_pstate_limits_lock);
+	driver_registered = true;
+	mutex_unlock(&intel_pstate_limits_lock);
+
+	if (intel_pstate_driver == &intel_pstate && !hwp_active &&
+	    pstate_funcs.get_target_pstate != get_target_pstate_use_cpu_load)
+		intel_pstate_debug_expose_params();
+
+	return 0;
+}
+
+static int intel_pstate_unregister_driver(void)
+{
+	if (hwp_active)
+		return -EBUSY;
+
+	if (intel_pstate_driver == &intel_pstate && !hwp_active &&
+	    pstate_funcs.get_target_pstate != get_target_pstate_use_cpu_load)
+		intel_pstate_debug_hide_params();
+
+	mutex_lock(&intel_pstate_limits_lock);
+	driver_registered = false;
+	mutex_unlock(&intel_pstate_limits_lock);
+
+	cpufreq_unregister_driver(intel_pstate_driver);
+	intel_pstate_driver_cleanup();
+
+	return 0;
+}
+
+static ssize_t intel_pstate_show_status(char *buf)
+{
+	if (!driver_registered)
+		return sprintf(buf, "off\n");
+
+	return sprintf(buf, "%s\n", intel_pstate_driver == &intel_pstate ?
+					"active" : "passive");
+}
+
+static int intel_pstate_update_status(const char *buf, size_t size)
+{
+	int ret;
+
+	if (size == 3 && !strncmp(buf, "off", size))
+		return driver_registered ?
+			intel_pstate_unregister_driver() : -EINVAL;
+
+	if (size == 6 && !strncmp(buf, "active", size)) {
+		if (driver_registered) {
+			if (intel_pstate_driver == &intel_pstate)
+				return 0;
+
+			ret = intel_pstate_unregister_driver();
+			if (ret)
+				return ret;
+		}
+
+		intel_pstate_driver = &intel_pstate;
+		return intel_pstate_register_driver();
+	}
+
+	if (size == 7 && !strncmp(buf, "passive", size)) {
+		if (driver_registered) {
+			if (intel_pstate_driver != &intel_pstate)
+				return 0;
+
+			ret = intel_pstate_unregister_driver();
+			if (ret)
+				return ret;
+		}
+
+		intel_pstate_driver = &intel_cpufreq;
+		return intel_pstate_register_driver();
+	}
+
+	return -EINVAL;
+}
+
 static int no_load __initdata;
 static int no_hwp __initdata;
 static int hwp_only __initdata;
@@ -2503,9 +2659,9 @@ static const struct x86_cpu_id hwp_suppo
 
 static int __init intel_pstate_init(void)
 {
-	int cpu, rc = 0;
 	const struct x86_cpu_id *id;
 	struct cpu_defaults *cpu_def;
+	int rc = 0;
 
 	if (no_load)
 		return -ENODEV;
@@ -2537,49 +2693,29 @@ hwp_cpu_matched:
 	if (intel_pstate_platform_pwr_mgmt_exists())
 		return -ENODEV;
 
+	if (!hwp_active && hwp_only)
+		return -ENOTSUPP;
+
 	pr_info("Intel P-state driver initializing\n");
 
 	all_cpu_data = vzalloc(sizeof(void *) * num_possible_cpus());
 	if (!all_cpu_data)
 		return -ENOMEM;
 
-	if (!hwp_active && hwp_only)
-		goto out;
-
 	intel_pstate_request_control_from_smm();
 
 	intel_pstate_sysfs_expose_params();
 
-	rc = cpufreq_register_driver(intel_pstate_driver);
-	if (rc)
-		goto out;
-
 	mutex_lock(&intel_pstate_driver_lock);
-	driver_registered = true;
+	rc = intel_pstate_register_driver();
 	mutex_unlock(&intel_pstate_driver_lock);
-
-	if (intel_pstate_driver == &intel_pstate && !hwp_active &&
-	    pstate_funcs.get_target_pstate != get_target_pstate_use_cpu_load)
-		intel_pstate_debug_expose_params();
+	if (rc)
+		return rc;
 
 	if (hwp_active)
 		pr_info("HWP enabled\n");
 
-	return rc;
-out:
-	get_online_cpus();
-	for_each_online_cpu(cpu) {
-		if (all_cpu_data[cpu]) {
-			if (intel_pstate_driver == &intel_pstate)
-				intel_pstate_clear_update_util_hook(cpu);
-
-			kfree(all_cpu_data[cpu]);
-		}
-	}
-
-	put_online_cpus();
-	vfree(all_cpu_data);
-	return -ENODEV;
+	return 0;
 }
 device_initcall(intel_pstate_init);
 
Index: linux-pm/Documentation/cpu-freq/intel-pstate.txt
===================================================================
--- linux-pm.orig/Documentation/cpu-freq/intel-pstate.txt
+++ linux-pm/Documentation/cpu-freq/intel-pstate.txt
@@ -85,6 +85,21 @@ Sysfs will show :
 Refer to "Intel® 64 and IA-32 Architectures Software Developer’s Manual
 Volume 3: System Programming Guide" to understand ratios.
 
+There is one more sysfs attribute in /sys/devices/system/cpu/intel_pstate/
+that can be used for controlling the operation mode of the driver:
+
+      status: Three settings are possible:
+      "off"     - The driver is not in use at this time.
+      "active"  - The driver works as a P-state governor (default).
+      "passive" - The driver works as a regular cpufreq one and collaborates
+                  with the generic cpufreq governors (it sets P-states as
+                  requested by those governors).
+      The current setting is returned by reads from this attribute.  Writing one
+      of the above strings to it changes the operation mode as indicated by that
+      string, if possible.  If HW-managed P-states (HWP) are enabled, it is not
+      possible to change the driver's operation mode and attempts to write to
+      this attribute will fail.
+
 cpufreq sysfs for Intel P-State
 
 Since this driver registers with cpufreq, cpufreq sysfs is also presented.
