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01bad1c689
If need_resched() returns "false", breaking out of the loop in poll_idle() will cause a new idle state to be selected, so in fact it usually doesn't make sense to spin in it longer than the target residency of the second state. [Note that the "polling" state is used only if there is at least one "real" state defined in addition to it, so the second state is always there.] On the other hand, breaking out of it early (say in case the next state is disabled) shouldn't hurt as it is polling anyway. For this reason, make the loop in poll_idle() break if the CPU has been spinning longer than the target residency of the second state (the "polling" state can only be state[0]). Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
56 lines
1.3 KiB
C
56 lines
1.3 KiB
C
/*
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* poll_state.c - Polling idle state
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/cpuidle.h>
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#include <linux/sched.h>
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#include <linux/sched/clock.h>
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#include <linux/sched/idle.h>
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#define POLL_IDLE_RELAX_COUNT 200
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static int __cpuidle poll_idle(struct cpuidle_device *dev,
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struct cpuidle_driver *drv, int index)
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{
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u64 time_start = local_clock();
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dev->poll_time_limit = false;
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local_irq_enable();
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if (!current_set_polling_and_test()) {
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u64 limit = (u64)drv->states[1].target_residency * NSEC_PER_USEC;
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unsigned int loop_count = 0;
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while (!need_resched()) {
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cpu_relax();
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if (loop_count++ < POLL_IDLE_RELAX_COUNT)
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continue;
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loop_count = 0;
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if (local_clock() - time_start > limit) {
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dev->poll_time_limit = true;
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break;
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}
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}
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}
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current_clr_polling();
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return index;
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}
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void cpuidle_poll_state_init(struct cpuidle_driver *drv)
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{
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struct cpuidle_state *state = &drv->states[0];
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snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
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snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
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state->exit_latency = 0;
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state->target_residency = 0;
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state->power_usage = -1;
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state->enter = poll_idle;
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state->disabled = false;
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state->flags = CPUIDLE_FLAG_POLLING;
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}
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EXPORT_SYMBOL_GPL(cpuidle_poll_state_init);
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