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_TIME_LIMIT    (TICK_NSEC / 16)
  13 #define POLL_IDLE_RELAX_COUNT   200
  14
  15 static int __cpuidle poll_idle(struct cpuidle_device *dev,
  16                                struct cpuidle_driver *drv, int index)
  17 {
  18         u64 time_start = local_clock();
  19
  20         dev->poll_time_limit = false;
  21
  22         local_irq_enable();
  23         if (!current_set_polling_and_test()) {
  24                 unsigned int loop_count = 0;
  25
  26                 while (!need_resched()) {
  27                         cpu_relax();
  28                         if (loop_count++ < POLL_IDLE_RELAX_COUNT)
  29                                 continue;
  30
  31                         loop_count = 0;
  32                         if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) {
  33                                 dev->poll_time_limit = true;
  34                                 break;
  35                         }
  36                 }
  37         }
  38         current_clr_polling();
  39
  40         return index;
  41 }
  42
  43 void cpuidle_poll_state_init(struct cpuidle_driver *drv)
  44 {
  45         struct cpuidle_state *state = &drv->states[0];
  46
  47         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
  48         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
  49         state->exit_latency = 0;
  50         state->target_residency = 0;
  51         state->power_usage = -1;
  52         state->enter = poll_idle;
  53         state->disabled = false;
  54         state->flags = CPUIDLE_FLAG_POLLING;
  55 }
  56 EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);