drivers/cpuidle/poll_state.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * poll_state.c - Polling idle state
   4  */
   5
   6 #include <linux/cpuidle.h>
   7 #include <linux/sched.h>
   8 #include <linux/sched/clock.h>
   9 #include <linux/sched/idle.h>
  10
  11 #define POLL_IDLE_RELAX_COUNT   200
  12
  13 static int __cpuidle poll_idle(struct cpuidle_device *dev,
  14                                struct cpuidle_driver *drv, int index)
  15 {
  16         u64 time_start = local_clock();
  17
  18         dev->poll_time_limit = false;
  19
  20         local_irq_enable();
  21         if (!current_set_polling_and_test()) {
  22                 unsigned int loop_count = 0;
  23                 u64 limit = TICK_NSEC;
  24                 int i;
  25
  26                 for (i = 1; i < drv->state_count; i++) {
  27                         if (drv->states[i].disabled || dev->states_usage[i].disable)
  28                                 continue;
  29
  30                         limit = (u64)drv->states[i].target_residency * NSEC_PER_USEC;
  31                         break;
  32                 }
  33
  34                 while (!need_resched()) {
  35                         cpu_relax();
  36                         if (loop_count++ < POLL_IDLE_RELAX_COUNT)
  37                                 continue;
  38
  39                         loop_count = 0;
  40                         if (local_clock() - time_start > limit) {
  41                                 dev->poll_time_limit = true;
  42                                 break;
  43                         }
  44                 }
  45         }
  46         current_clr_polling();
  47
  48         return index;
  49 }
  50
  51 void cpuidle_poll_state_init(struct cpuidle_driver *drv)
  52 {
  53         struct cpuidle_state *state = &drv->states[0];
  54
  55         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
  56         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
  57         state->exit_latency = 0;
  58         state->target_residency = 0;
  59         state->power_usage = -1;
  60         state->enter = poll_idle;
  61         state->disabled = false;
  62         state->flags = CPUIDLE_FLAG_POLLING;
  63 }
  64 EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);