Quelle  cpuidle-cps.c   Sprache: C

// 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\n");
   break;
  case STATE_NC_WAIT:
   pr_cont("non-coherent wait\n");
   break;
  case STATE_CLOCK_GATED:
   pr_cont("clock gating\n");
   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\n");
  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\n",
          cpu);
   goto err_out;
  }
 }

 return 0;
err_out:
 cps_cpuidle_unregister();
 return err;
}
device_initcall(cps_cpuidle_init);