cpufreq: Simplify cpufreq_add_dev()

Currently cpufreq_add_dev() firsts allocates policy, calls
driver->init() and then checks if this CPU is already managed or not.
And if it is already managed, its policy is freed.

We can save all this if we somehow know that CPU is managed or not in
advance.  policy->related_cpus contains the list of all valid sibling
CPUs of policy->cpu. We can check this to see if the current CPU is
already managed.

From now on, platforms don't really need to set related_cpus from
their init() routines, as the same work is done by core too.

If a platform driver needs to set the related_cpus mask with some
additional CPUs, other than CPUs present in policy->cpus, they are
free to do it, though, as we don't override anything.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -552,8 +552,6 @@ static ssize_t show_cpus(const struct cpumask *mask, char *buf)
  */
 static ssize_t show_related_cpus(struct cpufreq_policy *policy, char *buf)
 {
-	if (cpumask_empty(policy->related_cpus))
-		return show_cpus(policy->cpus, buf);
 	return show_cpus(policy->related_cpus, buf);
 }
 
@@ -709,92 +707,6 @@ static struct kobj_type ktype_cpufreq = {
 	.release	= cpufreq_sysfs_release,
 };
 
-/*
- * Returns:
- *   Negative: Failure
- *   0:        Success
- *   Positive: When we have a managed CPU and the sysfs got symlinked
- */
-static int cpufreq_add_dev_policy(unsigned int cpu,
-				  struct cpufreq_policy *policy,
-				  struct device *dev)
-{
-	int ret = 0;
-#ifdef CONFIG_SMP
-	unsigned long flags;
-	unsigned int j;
-#ifdef CONFIG_HOTPLUG_CPU
-	struct cpufreq_governor *gov;
-
-	gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
-	if (gov) {
-		policy->governor = gov;
-		pr_debug("Restoring governor %s for cpu %d\n",
-		       policy->governor->name, cpu);
-	}
-#endif
-
-	for_each_cpu(j, policy->cpus) {
-		struct cpufreq_policy *managed_policy;
-
-		if (cpu == j)
-			continue;
-
-		/* Check for existing affected CPUs.
-		 * They may not be aware of it due to CPU Hotplug.
-		 * cpufreq_cpu_put is called when the device is removed
-		 * in __cpufreq_remove_dev()
-		 */
-		managed_policy = cpufreq_cpu_get(j);
-		if (unlikely(managed_policy)) {
-
-			/* Set proper policy_cpu */
-			unlock_policy_rwsem_write(cpu);
-			per_cpu(cpufreq_policy_cpu, cpu) = managed_policy->cpu;
-
-			if (lock_policy_rwsem_write(cpu) < 0) {
-				/* Should not go through policy unlock path */
-				if (cpufreq_driver->exit)
-					cpufreq_driver->exit(policy);
-				cpufreq_cpu_put(managed_policy);
-				return -EBUSY;
-			}
-
-			__cpufreq_governor(managed_policy, CPUFREQ_GOV_STOP);
-
-			spin_lock_irqsave(&cpufreq_driver_lock, flags);
-			cpumask_copy(managed_policy->cpus, policy->cpus);
-			per_cpu(cpufreq_cpu_data, cpu) = managed_policy;
-			spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
-
-			__cpufreq_governor(managed_policy, CPUFREQ_GOV_START);
-			__cpufreq_governor(managed_policy, CPUFREQ_GOV_LIMITS);
-
-			pr_debug("CPU already managed, adding link\n");
-			ret = sysfs_create_link(&dev->kobj,
-						&managed_policy->kobj,
-						"cpufreq");
-			if (ret)
-				cpufreq_cpu_put(managed_policy);
-			/*
-			 * Success. We only needed to be added to the mask.
-			 * Call driver->exit() because only the cpu parent of
-			 * the kobj needed to call init().
-			 */
-			if (cpufreq_driver->exit)
-				cpufreq_driver->exit(policy);
-
-			if (!ret)
-				return 1;
-			else
-				return ret;
-		}
-	}
-#endif
-	return ret;
-}
-
-
 /* symlink affected CPUs */
 static int cpufreq_add_dev_symlink(unsigned int cpu,
 				   struct cpufreq_policy *policy)
@@ -899,6 +811,42 @@ err_out_kobj_put:
 	return ret;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
+				  struct device *dev)
+{
+	struct cpufreq_policy *policy;
+	int ret = 0;
+	unsigned long flags;
+
+	policy = cpufreq_cpu_get(sibling);
+	WARN_ON(!policy);
+
+	per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
+
+	lock_policy_rwsem_write(cpu);
+
+	__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+
+	spin_lock_irqsave(&cpufreq_driver_lock, flags);
+	cpumask_set_cpu(cpu, policy->cpus);
+	per_cpu(cpufreq_cpu_data, cpu) = policy;
+	spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+	__cpufreq_governor(policy, CPUFREQ_GOV_START);
+	__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+
+	unlock_policy_rwsem_write(cpu);
+
+	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
+	if (ret) {
+		cpufreq_cpu_put(policy);
+		return ret;
+	}
+
+	return 0;
+}
+#endif
 
 /**
  * cpufreq_add_dev - add a CPU device
@@ -911,12 +859,12 @@ err_out_kobj_put:
  */
 static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 {
-	unsigned int cpu = dev->id;
+	unsigned int j, cpu = dev->id;
-	int ret = 0, found = 0;
+	int ret = -ENOMEM, found = 0;
 	struct cpufreq_policy *policy;
 	unsigned long flags;
-	unsigned int j;
 #ifdef CONFIG_HOTPLUG_CPU
+	struct cpufreq_governor *gov;
 	int sibling;
 #endif
 
@@ -933,6 +881,15 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 		cpufreq_cpu_put(policy);
 		return 0;
 	}
+
+#ifdef CONFIG_HOTPLUG_CPU
+	/* Check if this cpu was hot-unplugged earlier and has siblings */
+	for_each_online_cpu(sibling) {
+		struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
+		if (cp && cpumask_test_cpu(cpu, cp->related_cpus))
+			return cpufreq_add_policy_cpu(cpu, sibling, dev);
+	}
+#endif
 #endif
 
 	if (!try_module_get(cpufreq_driver->owner)) {
@@ -940,7 +897,6 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 		goto module_out;
 	}
 
-	ret = -ENOMEM;
 	policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
 	if (!policy)
 		goto nomem_out;
@@ -985,6 +941,9 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 		goto err_unlock_policy;
 	}
 
+	/* related cpus should atleast have policy->cpus */
+	cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);
+
 	/*
 	 * affected cpus must always be the one, which are online. We aren't
 	 * managing offline cpus here.
@@ -997,14 +956,14 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
 				     CPUFREQ_START, policy);
 
-	ret = cpufreq_add_dev_policy(cpu, policy, dev);
+#ifdef CONFIG_HOTPLUG_CPU
-	if (ret) {
+	gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
-		if (ret > 0)
+	if (gov) {
-			/* This is a managed cpu, symlink created,
+		policy->governor = gov;
-			   exit with 0 */
+		pr_debug("Restoring governor %s for cpu %d\n",
-			ret = 0;
+		       policy->governor->name, cpu);
-		goto err_unlock_policy;
 	}
+#endif
 
 	ret = cpufreq_add_dev_interface(cpu, policy, dev);
 	if (ret)
@@ -1018,7 +977,6 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 
 	return 0;
 
-
 err_out_unregister:
 	spin_lock_irqsave(&cpufreq_driver_lock, flags);
 	for_each_cpu(j, policy->cpus)

drivers/cpufreq/spear-cpufreq.c

@@ -189,7 +189,6 @@ static int spear_cpufreq_init(struct cpufreq_policy *policy)
 	policy->cur = spear_cpufreq_get(0);
 
 	cpumask_copy(policy->cpus, topology_core_cpumask(policy->cpu));
-	cpumask_copy(policy->related_cpus, policy->cpus);
 
 	return 0;
 }