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         local_irq_enable();
  21         if (!current_set_polling_and_test()) {
  22                 unsigned int loop_count = 0;
  23
  24                 while (!need_resched()) {
  25                         cpu_relax();
  26                         if (loop_count++ < POLL_IDLE_RELAX_COUNT)
  27                                 continue;
  28
  29                         loop_count = 0;
  30                         if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT)
  31                                 break;
  32                 }
  33         }
  34         current_clr_polling();
  35
  36         return index;
  37 }
  38
  39 void cpuidle_poll_state_init(struct cpuidle_driver *drv)
  40 {
  41         struct cpuidle_state *state = &drv->states[0];
  42
  43         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
  44         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
  45         state->exit_latency = 0;
  46         state->target_residency = 0;
  47         state->power_usage = -1;
  48         state->enter = poll_idle;
  49         state->disabled = false;
  50         state->flags = CPUIDLE_FLAG_POLLING;
  51 }
  52 EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);