static int __init intel_idle_init()

in intel_idle.c [1699:1783]

• 67 lines of code
• 19 McCabe index (conditional complexity)

static int __init intel_idle_init(void)
{
	const struct x86_cpu_id *id;
	unsigned int eax, ebx, ecx;
	int retval;

	/* Do not load intel_idle at all for now if idle= is passed */
	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
		return -ENODEV;

	if (max_cstate == 0) {
		pr_debug("disabled\n");
		return -EPERM;
	}

	id = x86_match_cpu(intel_idle_ids);
	if (id) {
		if (!boot_cpu_has(X86_FEATURE_MWAIT)) {
			pr_debug("Please enable MWAIT in BIOS SETUP\n");
			return -ENODEV;
		}
	} else {
		id = x86_match_cpu(intel_mwait_ids);
		if (!id)
			return -ENODEV;
	}

	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
		return -ENODEV;

	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);

	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
	    !(ecx & CPUID5_ECX_INTERRUPT_BREAK) ||
	    !mwait_substates)
			return -ENODEV;

	pr_debug("MWAIT substates: 0x%x\n", mwait_substates);

	icpu = (const struct idle_cpu *)id->driver_data;
	if (icpu) {
		cpuidle_state_table = icpu->state_table;
		auto_demotion_disable_flags = icpu->auto_demotion_disable_flags;
		disable_promotion_to_c1e = icpu->disable_promotion_to_c1e;
		if (icpu->use_acpi || force_use_acpi)
			intel_idle_acpi_cst_extract();
	} else if (!intel_idle_acpi_cst_extract()) {
		return -ENODEV;
	}

	pr_debug("v" INTEL_IDLE_VERSION " model 0x%X\n",
		 boot_cpu_data.x86_model);

	intel_idle_cpuidle_devices = alloc_percpu(struct cpuidle_device);
	if (!intel_idle_cpuidle_devices)
		return -ENOMEM;

	intel_idle_cpuidle_driver_init(&intel_idle_driver);

	retval = cpuidle_register_driver(&intel_idle_driver);
	if (retval) {
		struct cpuidle_driver *drv = cpuidle_get_driver();
		printk(KERN_DEBUG pr_fmt("intel_idle yielding to %s\n"),
		       drv ? drv->name : "none");
		goto init_driver_fail;
	}

	retval = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "idle/intel:online",
				   intel_idle_cpu_online, NULL);
	if (retval < 0)
		goto hp_setup_fail;

	pr_debug("Local APIC timer is reliable in %s\n",
		 boot_cpu_has(X86_FEATURE_ARAT) ? "all C-states" : "C1");

	return 0;

hp_setup_fail:
	intel_idle_cpuidle_devices_uninit();
	cpuidle_unregister_driver(&intel_idle_driver);
init_driver_fail:
	free_percpu(intel_idle_cpuidle_devices);
	return retval;

}