// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * Copyright (C) 2014 Imagination Technologies

   * Author: Paul Burton <paul.burton@mips.com>

   */
  
  #include <linux/cpu_pm.h>
  #include <linux/cpuidle.h>
  #include <linux/init.h>
  
  #include <asm/idle.h>
  #include <asm/pm-cps.h>
  
  /* Enumeration of the various idle states this driver may enter */
  enum cps_idle_state {
  	STATE_WAIT = 0,		/* MIPS wait instruction, coherent */
  	STATE_NC_WAIT,		/* MIPS wait instruction, non-coherent */
  	STATE_CLOCK_GATED,	/* Core clock gated */
  	STATE_POWER_GATED,	/* Core power gated */
  	STATE_COUNT
  };
  
  static int cps_nc_enter(struct cpuidle_device *dev,
  			struct cpuidle_driver *drv, int index)
  {
  	enum cps_pm_state pm_state;
  	int err;
  
  	/*
  	 * At least one core must remain powered up & clocked in order for the
  	 * system to have any hope of functioning.
  	 *
  	 * TODO: don't treat core 0 specially, just prevent the final core
  	 * TODO: remap interrupt affinity temporarily
  	 */

  	if (cpus_are_siblings(0, dev->cpu) && (index > STATE_NC_WAIT))

  		index = STATE_NC_WAIT;
  
  	/* Select the appropriate cps_pm_state */
  	switch (index) {
  	case STATE_NC_WAIT:
  		pm_state = CPS_PM_NC_WAIT;
  		break;
  	case STATE_CLOCK_GATED:
  		pm_state = CPS_PM_CLOCK_GATED;
  		break;
  	case STATE_POWER_GATED:
  		pm_state = CPS_PM_POWER_GATED;
  		break;
  	default:
  		BUG();
  		return -EINVAL;
  	}
  
  	/* Notify listeners the CPU is about to power down */
  	if ((pm_state == CPS_PM_POWER_GATED) && cpu_pm_enter())
  		return -EINTR;
  
  	/* Enter that state */
  	err = cps_pm_enter_state(pm_state);
  
  	/* Notify listeners the CPU is back up */
  	if (pm_state == CPS_PM_POWER_GATED)
  		cpu_pm_exit();
  
  	return err ?: index;
  }
  
  static struct cpuidle_driver cps_driver = {
  	.name			= "cpc_cpuidle",
  	.owner			= THIS_MODULE,
  	.states = {
  		[STATE_WAIT] = MIPS_CPUIDLE_WAIT_STATE,
  		[STATE_NC_WAIT] = {
  			.enter	= cps_nc_enter,
  			.exit_latency		= 200,
  			.target_residency	= 450,

  			.name	= "nc-wait",
  			.desc	= "non-coherent MIPS wait",
  		},
  		[STATE_CLOCK_GATED] = {
  			.enter	= cps_nc_enter,
  			.exit_latency		= 300,
  			.target_residency	= 700,

  			.flags	= CPUIDLE_FLAG_TIMER_STOP,

  			.name	= "clock-gated",
  			.desc	= "core clock gated",
  		},
  		[STATE_POWER_GATED] = {
  			.enter	= cps_nc_enter,
  			.exit_latency		= 600,
  			.target_residency	= 1000,

  			.flags	= CPUIDLE_FLAG_TIMER_STOP,

  			.name	= "power-gated",
  			.desc	= "core power gated",
  		},
  	},
  	.state_count		= STATE_COUNT,
  	.safe_state_index	= 0,
  };
  
  static void __init cps_cpuidle_unregister(void)
  {
  	int cpu;
  	struct cpuidle_device *device;
  
  	for_each_possible_cpu(cpu) {
  		device = &per_cpu(cpuidle_dev, cpu);
  		cpuidle_unregister_device(device);
  	}
  
  	cpuidle_unregister_driver(&cps_driver);
  }
  
  static int __init cps_cpuidle_init(void)
  {

  	int err, cpu, i;

  	struct cpuidle_device *device;
  
  	/* Detect supported states */
  	if (!cps_pm_support_state(CPS_PM_POWER_GATED))
  		cps_driver.state_count = STATE_CLOCK_GATED + 1;
  	if (!cps_pm_support_state(CPS_PM_CLOCK_GATED))
  		cps_driver.state_count = STATE_NC_WAIT + 1;
  	if (!cps_pm_support_state(CPS_PM_NC_WAIT))
  		cps_driver.state_count = STATE_WAIT + 1;
  
  	/* Inform the user if some states are unavailable */
  	if (cps_driver.state_count < STATE_COUNT) {
  		pr_info("cpuidle-cps: limited to ");
  		switch (cps_driver.state_count - 1) {
  		case STATE_WAIT:
  			pr_cont("coherent wait
  ");
  			break;
  		case STATE_NC_WAIT:
  			pr_cont("non-coherent wait
  ");
  			break;
  		case STATE_CLOCK_GATED:
  			pr_cont("clock gating
  ");
  			break;
  		}
  	}
  
  	/*
  	 * Set the coupled flag on the appropriate states if this system
  	 * requires it.
  	 */
  	if (coupled_coherence)
  		for (i = STATE_NC_WAIT; i < cps_driver.state_count; i++)
  			cps_driver.states[i].flags |= CPUIDLE_FLAG_COUPLED;
  
  	err = cpuidle_register_driver(&cps_driver);
  	if (err) {
  		pr_err("Failed to register CPS cpuidle driver
  ");
  		return err;
  	}
  
  	for_each_possible_cpu(cpu) {

  		device = &per_cpu(cpuidle_dev, cpu);
  		device->cpu = cpu;

  #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED

  		cpumask_copy(&device->coupled_cpus, &cpu_sibling_map[cpu]);
  #endif
  
  		err = cpuidle_register_device(device);
  		if (err) {
  			pr_err("Failed to register CPU%d cpuidle device
  ",
  			       cpu);
  			goto err_out;
  		}
  	}
  
  	return 0;
  err_out:
  	cps_cpuidle_unregister();
  	return err;
  }
  device_initcall(cps_cpuidle_init);