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01c162e27a
Introduce generic cpuidle driver on s390. Use a two stage approach to handle idle scenarios and use idle governor for idle stage selection. Two stages are, from shallow to deep, idle polling and enabled wait. Suggested-by: Christian Borntraeger <borntraeger@linux.ibm.com> Suggested-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Mete Durlu <meted@linux.ibm.com> Reviewed-by: Heiko Carstens <hca@linux.ibm.com> Reviewed-by: Christian Loehle <christian.loehle@arm.com> Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
116 lines
2.7 KiB
C
116 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* s390 generic CPU idle driver.
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*
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* Copyright IBM Corp. 2026
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*/
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#define pr_fmt(fmt) "CPUidle s390: " fmt
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#include <linux/init.h>
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#include <linux/cpuidle.h>
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#include <linux/cpu.h>
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#include <linux/sched/clock.h>
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static __cpuidle int s390_enter_idle(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index)
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{
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arch_cpu_idle();
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return index;
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}
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static struct cpuidle_driver s390_cpuidle_driver = {
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.cpumask = (struct cpumask *)cpu_present_mask,
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.name = "s390-idle",
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.states = {
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{ /* entry 0 is for polling */},
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{
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.enter = s390_enter_idle,
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.name = "IDLE",
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.desc = "ENABLED WAIT",
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},
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},
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.safe_state_index = 0,
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.state_count = 2,
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};
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static int s390_cpuidle_cpu_online(unsigned int cpu)
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{
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struct cpuidle_device *dev = &per_cpu(cpuidle_dev, cpu);
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int rc;
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if (dev->registered) {
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cpuidle_pause_and_lock();
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rc = cpuidle_enable_device(dev);
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cpuidle_resume_and_unlock();
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if (rc)
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pr_err("Failed to enable cpuidle device on cpu %u\n", cpu);
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} else {
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dev->cpu = cpu;
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rc = cpuidle_register_device(dev);
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if (rc)
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pr_err("Failed to register cpuidle driver on cpu %u\n", cpu);
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}
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return rc;
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}
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static int s390_cpuidle_cpu_dead(unsigned int cpu)
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{
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struct cpuidle_device *dev = &per_cpu(cpuidle_dev, cpu);
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if (!dev->registered)
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return 0;
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cpuidle_pause_and_lock();
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cpuidle_disable_device(dev);
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cpuidle_resume_and_unlock();
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return 0;
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}
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/*
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* The target_residency and exit_latency values are benchmark-derived estimates
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* that remain non-deterministic due to s390's virtualized architecture.
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*
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* Configuration strategy:
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* - Poll idle state: Values derived from the next enabled idle state (EW)
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* - Enabled Wait state: Values selected based on idle behavior and empirical
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* measurement data
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*
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* Goal is to improve responsiveness for workloads with frequent sleep/wakeup
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* cycles while minimizing any side effects.
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*/
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static void __init s390_cpuidle_ew_tune(void)
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{
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struct cpuidle_state *state = &s390_cpuidle_driver.states[1];
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if (machine_is_lpar()) {
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state->target_residency = 5;
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state->exit_latency = 5;
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} else {
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state->target_residency = 1;
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state->exit_latency = 1;
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}
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}
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static int __init s390_cpuidle_init(void)
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{
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int rc;
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s390_cpuidle_ew_tune();
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cpuidle_poll_state_init(&s390_cpuidle_driver);
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rc = cpuidle_register(&s390_cpuidle_driver, NULL);
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if (rc)
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return rc;
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rc = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
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"cpuidle/s390:online",
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s390_cpuidle_cpu_online,
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s390_cpuidle_cpu_dead);
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if (rc < 0) {
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cpuidle_unregister(&s390_cpuidle_driver);
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pr_err("Failed to allocate hotplug state: cpuidle/s390:online\n");
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return rc;
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}
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return 0;
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}
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device_initcall(s390_cpuidle_init);
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