// SPDX-License-Identifier: GPL-2.0
  /*
   * cpuidle driver for haltpoll governor.
   *
   * Copyright 2019 Red Hat, Inc. and/or its affiliates.
   *
   * This work is licensed under the terms of the GNU GPL, version 2.  See
   * the COPYING file in the top-level directory.
   *
   * Authors: Marcelo Tosatti <mtosatti@redhat.com>
   */
  
  #include <linux/init.h>

  #include <linux/cpu.h>

  #include <linux/cpuidle.h>
  #include <linux/module.h>
  #include <linux/sched/idle.h>
  #include <linux/kvm_para.h>

  #include <linux/cpuidle_haltpoll.h>

  static bool force __read_mostly;
  module_param(force, bool, 0444);
  MODULE_PARM_DESC(force, "Load unconditionally");

  static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
  static enum cpuhp_state haltpoll_hp_state;

  static int default_enter_idle(struct cpuidle_device *dev,
  			      struct cpuidle_driver *drv, int index)
  {
  	if (current_clr_polling_and_test()) {
  		local_irq_enable();
  		return index;
  	}
  	default_idle();
  	return index;
  }
  
  static struct cpuidle_driver haltpoll_driver = {
  	.name = "haltpoll",

  	.governor = "haltpoll",

  	.states = {
  		{ /* entry 0 is for polling */ },
  		{
  			.enter			= default_enter_idle,
  			.exit_latency		= 1,
  			.target_residency	= 1,
  			.power_usage		= -1,
  			.name			= "haltpoll idle",
  			.desc			= "default architecture idle",
  		},
  	},
  	.safe_state_index = 0,
  	.state_count = 2,
  };

  static int haltpoll_cpu_online(unsigned int cpu)
  {
  	struct cpuidle_device *dev;
  
  	dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
  	if (!dev->registered) {
  		dev->cpu = cpu;
  		if (cpuidle_register_device(dev)) {
  			pr_notice("cpuidle_register_device %d failed!
  ", cpu);
  			return -EIO;
  		}
  		arch_haltpoll_enable(cpu);
  	}
  
  	return 0;
  }
  
  static int haltpoll_cpu_offline(unsigned int cpu)
  {
  	struct cpuidle_device *dev;
  
  	dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
  	if (dev->registered) {
  		arch_haltpoll_disable(cpu);
  		cpuidle_unregister_device(dev);
  	}
  
  	return 0;
  }
  
  static void haltpoll_uninit(void)
  {
  	if (haltpoll_hp_state)
  		cpuhp_remove_state(haltpoll_hp_state);
  	cpuidle_unregister_driver(&haltpoll_driver);
  
  	free_percpu(haltpoll_cpuidle_devices);
  	haltpoll_cpuidle_devices = NULL;
  }

  static bool haltpoll_want(void)

  {
  	return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
  }

  static int __init haltpoll_init(void)
  {

  	int ret;

  	struct cpuidle_driver *drv = &haltpoll_driver;

  	/* Do not load haltpoll if idle= is passed */
  	if (boot_option_idle_override != IDLE_NO_OVERRIDE)
  		return -ENODEV;

  	cpuidle_poll_state_init(drv);

  	if (!kvm_para_available() || !haltpoll_want())

  		return -ENODEV;

  	ret = cpuidle_register_driver(drv);
  	if (ret < 0)
  		return ret;
  
  	haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
  	if (haltpoll_cpuidle_devices == NULL) {
  		cpuidle_unregister_driver(drv);
  		return -ENOMEM;
  	}
  
  	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "cpuidle/haltpoll:online",
  				haltpoll_cpu_online, haltpoll_cpu_offline);
  	if (ret < 0) {
  		haltpoll_uninit();
  	} else {
  		haltpoll_hp_state = ret;
  		ret = 0;
  	}

  
  	return ret;

  }
  
  static void __exit haltpoll_exit(void)
  {

  	haltpoll_uninit();

  }
  
  module_init(haltpoll_init);
  module_exit(haltpoll_exit);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");