drivers/cpuidle/poll_state.c

   1 /*
   2  * poll_state.c - Polling idle state
   3  *
   4  * This file is released under the GPLv2.
   5  */
   6
   7 #include <linux/cpuidle.h>
   8 #include <linux/sched.h>
   9 #include <linux/sched/clock.h>
  10 #include <linux/sched/idle.h>
  11
  12 #define POLL_IDLE_RELAX_COUNT   200
  13
  14 static int __cpuidle poll_idle(struct cpuidle_device *dev,
  15                                struct cpuidle_driver *drv, int index)
  16 {
  17         u64 time_start = local_clock();
  18
  19         dev->poll_time_limit = false;
  20
  21         local_irq_enable();
  22         if (!current_set_polling_and_test()) {
  23                 unsigned int loop_count = 0;
  24                 u64 limit = TICK_NSEC;
  25                 int i;
  26
  27                 for (i = 1; i < drv->state_count; i++) {
  28                         if (drv->states[i].disabled || dev->states_usage[i].disable)
  29                                 continue;
  30
  31                         limit = (u64)drv->states[i].target_residency * NSEC_PER_USEC;
  32                         break;
  33                 }
  34
  35                 while (!need_resched()) {
  36                         cpu_relax();
  37                         if (loop_count++ < POLL_IDLE_RELAX_COUNT)
  38                                 continue;
  39
  40                         loop_count = 0;
  41                         if (local_clock() - time_start > limit) {
  42                                 dev->poll_time_limit = true;
  43                                 break;
  44                         }
  45                 }
  46         }
  47         current_clr_polling();
  48
  49         return index;
  50 }
  51
  52 void cpuidle_poll_state_init(struct cpuidle_driver *drv)
  53 {
  54         struct cpuidle_state *state = &drv->states[0];
  55
  56         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
  57         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
  58         state->exit_latency = 0;
  59         state->target_residency = 0;
  60         state->power_usage = -1;
  61         state->enter = poll_idle;
  62         state->disabled = false;
  63         state->flags = CPUIDLE_FLAG_POLLING;
  64 }
  65 EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);