Merge tag 'acpi-6.18-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull ACPI fix from Rafael Wysocki:
 "Revert a commit that attempted to make the code in the ACPI processor
  driver more straightforward, but it turned out to cause the kernel to
  crash on at least one system, along with some further cleanups on top
  of it"

* tag 'acpi-6.18-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  Revert "ACPI: processor: idle: Optimize ACPI idle driver registration"
  Revert "ACPI: processor: Remove unused empty stubs of some functions"
  Revert "ACPI: processor: idle: Rearrange declarations in header file"
  Revert "ACPI: processor: idle: Redefine two functions as void"
  Revert "ACPI: processor: Do not expose global variable acpi_idle_driver"

Author: torvalds

drivers/acpi/processor_driver.c

@@ -166,7 +166,8 @@ static int __acpi_processor_start(struct acpi_device *device)
 	if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
 		dev_dbg(&device->dev, "CPPC data invalid or not present\n");
 
-	acpi_processor_power_init(pr);
+	if (cpuidle_get_driver() == &acpi_idle_driver)
+		acpi_processor_power_init(pr);
 
 	acpi_pss_perf_init(pr);
 
@@ -262,8 +263,6 @@ static int __init acpi_processor_driver_init(void)
 	if (result < 0)
 		return result;
 
-	acpi_processor_register_idle_driver();
-
 	result = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 				   "acpi/cpu-drv:online",
 				   acpi_soft_cpu_online, NULL);
@@ -302,7 +301,6 @@ static void __exit acpi_processor_driver_exit(void)
 
 	cpuhp_remove_state_nocalls(hp_online);
 	cpuhp_remove_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD);
-	acpi_processor_unregister_idle_driver();
 	driver_unregister(&acpi_processor_driver);
 }
 

drivers/acpi/processor_idle.c

@@ -51,7 +51,7 @@ module_param(latency_factor, uint, 0644);
 
 static DEFINE_PER_CPU(struct cpuidle_device *, acpi_cpuidle_device);
 
-static struct cpuidle_driver acpi_idle_driver = {
+struct cpuidle_driver acpi_idle_driver = {
 	.name =		"acpi_idle",
 	.owner =	THIS_MODULE,
 };
@@ -1357,102 +1357,79 @@ int acpi_processor_power_state_has_changed(struct acpi_processor *pr)
 	return 0;
 }
 
-void acpi_processor_register_idle_driver(void)
-{
-	struct acpi_processor *pr;
-	int ret = -ENODEV;
-	int cpu;
-
-	/*
-	 * Acpi idle driver is used by all possible CPUs.
-	 * Install the idle handler by the processor power info of one in them.
-	 * Note that we use previously set idle handler will be used on
-	 * platforms that only support C1.
-	 */
-	for_each_cpu(cpu, (struct cpumask *)cpu_possible_mask) {
-		pr = per_cpu(processors, cpu);
-		if (!pr)
-			continue;
-
-		ret = acpi_processor_get_power_info(pr);
-		if (!ret) {
-			pr->flags.power_setup_done = 1;
-			acpi_processor_setup_cpuidle_states(pr);
-			break;
-		}
-	}
-
-	if (ret) {
-		pr_debug("No ACPI power information from any CPUs.\n");
-		return;
-	}
+static int acpi_processor_registered;
 
-	ret = cpuidle_register_driver(&acpi_idle_driver);
-	if (ret) {
-		pr_debug("register %s failed.\n", acpi_idle_driver.name);
-		return;
-	}
-	pr_debug("%s registered with cpuidle.\n", acpi_idle_driver.name);
-}
-
-void acpi_processor_unregister_idle_driver(void)
-{
-	cpuidle_unregister_driver(&acpi_idle_driver);
-}
-
-void acpi_processor_power_init(struct acpi_processor *pr)
+int acpi_processor_power_init(struct acpi_processor *pr)
 {
+	int retval;
 	struct cpuidle_device *dev;
 
-	/*
-	 * The code below only works if the current cpuidle driver is the ACPI
-	 * idle driver.
-	 */
-	if (cpuidle_get_driver() != &acpi_idle_driver)
-		return;
-
 	if (disabled_by_idle_boot_param())
-		return;
+		return 0;
 
 	acpi_processor_cstate_first_run_checks();
 
 	if (!acpi_processor_get_power_info(pr))
 		pr->flags.power_setup_done = 1;
 
-	if (!pr->flags.power)
-		return;
-
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-	if (!dev)
-		return;
+	/*
+	 * Install the idle handler if processor power management is supported.
+	 * Note that we use previously set idle handler will be used on
+	 * platforms that only support C1.
+	 */
+	if (pr->flags.power) {
+		/* Register acpi_idle_driver if not already registered */
+		if (!acpi_processor_registered) {
+			acpi_processor_setup_cpuidle_states(pr);
+			retval = cpuidle_register_driver(&acpi_idle_driver);
+			if (retval)
+				return retval;
+			pr_debug("%s registered with cpuidle\n",
+				 acpi_idle_driver.name);
+		}
 
-	per_cpu(acpi_cpuidle_device, pr->id) = dev;
+		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+		if (!dev)
+			return -ENOMEM;
+		per_cpu(acpi_cpuidle_device, pr->id) = dev;
 
-	acpi_processor_setup_cpuidle_dev(pr, dev);
+		acpi_processor_setup_cpuidle_dev(pr, dev);
 
-	/*
-	 * Register a cpuidle device for this CPU.  The cpuidle driver using
-	 * this device is expected to be registered.
-	 */
-	if (cpuidle_register_device(dev)) {
-		per_cpu(acpi_cpuidle_device, pr->id) = NULL;
-		kfree(dev);
+		/* Register per-cpu cpuidle_device. Cpuidle driver
+		 * must already be registered before registering device
+		 */
+		retval = cpuidle_register_device(dev);
+		if (retval) {
+			if (acpi_processor_registered == 0)
+				cpuidle_unregister_driver(&acpi_idle_driver);
+
+			per_cpu(acpi_cpuidle_device, pr->id) = NULL;
+			kfree(dev);
+			return retval;
+		}
+		acpi_processor_registered++;
 	}
+	return 0;
 }
 
-void acpi_processor_power_exit(struct acpi_processor *pr)
+int acpi_processor_power_exit(struct acpi_processor *pr)
 {
 	struct cpuidle_device *dev = per_cpu(acpi_cpuidle_device, pr->id);
 
 	if (disabled_by_idle_boot_param())
-		return;
+		return 0;
 
 	if (pr->flags.power) {
 		cpuidle_unregister_device(dev);
+		acpi_processor_registered--;
+		if (acpi_processor_registered == 0)
+			cpuidle_unregister_driver(&acpi_idle_driver);
+
 		kfree(dev);
 	}
 
 	pr->flags.power_setup_done = 0;
+	return 0;
 }
 
 MODULE_IMPORT_NS("ACPI_PROCESSOR_IDLE");

include/acpi/processor.h

@@ -417,15 +417,32 @@ static inline void acpi_processor_throttling_init(void) {}
 #endif	/* CONFIG_ACPI_CPU_FREQ_PSS */
 
 /* in processor_idle.c */
+extern struct cpuidle_driver acpi_idle_driver;
 #ifdef CONFIG_ACPI_PROCESSOR_IDLE
-void acpi_processor_power_init(struct acpi_processor *pr);
-void acpi_processor_power_exit(struct acpi_processor *pr);
+int acpi_processor_power_init(struct acpi_processor *pr);
+int acpi_processor_power_exit(struct acpi_processor *pr);
 int acpi_processor_power_state_has_changed(struct acpi_processor *pr);
 int acpi_processor_hotplug(struct acpi_processor *pr);
-void acpi_processor_register_idle_driver(void);
-void acpi_processor_unregister_idle_driver(void);
-int acpi_processor_ffh_lpi_probe(unsigned int cpu);
-int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi);
+#else
+static inline int acpi_processor_power_init(struct acpi_processor *pr)
+{
+	return -ENODEV;
+}
+
+static inline int acpi_processor_power_exit(struct acpi_processor *pr)
+{
+	return -ENODEV;
+}
+
+static inline int acpi_processor_power_state_has_changed(struct acpi_processor *pr)
+{
+	return -ENODEV;
+}
+
+static inline int acpi_processor_hotplug(struct acpi_processor *pr)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_ACPI_PROCESSOR_IDLE */
 
 /* in processor_thermal.c */
@@ -448,6 +465,11 @@ static inline void acpi_thermal_cpufreq_exit(struct cpufreq_policy *policy)
 }
 #endif	/* CONFIG_CPU_FREQ */
 
+#ifdef CONFIG_ACPI_PROCESSOR_IDLE
+extern int acpi_processor_ffh_lpi_probe(unsigned int cpu);
+extern int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi);
+#endif
+
 void acpi_processor_init_invariance_cppc(void);
 
 #endif