1 // SPDX-License-Identifier: GPL-2.0
3 * cpuidle-pseries - idle state cpuidle driver.
4 * Adapted from drivers/idle/intel_idle.c and
5 * drivers/acpi/processor_idle.c
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/moduleparam.h>
13 #include <linux/cpuidle.h>
14 #include <linux/cpu.h>
15 #include <linux/notifier.h>
19 #include <asm/machdep.h>
20 #include <asm/firmware.h>
21 #include <asm/runlatch.h>
23 #include <asm/plpar_wrappers.h>
25 struct cpuidle_driver pseries_idle_driver = {
26 .name = "pseries_idle",
30 static int max_idle_state __read_mostly;
31 static struct cpuidle_state *cpuidle_state_table __read_mostly;
32 static u64 snooze_timeout __read_mostly;
33 static bool snooze_timeout_en __read_mostly;
35 static int snooze_loop(struct cpuidle_device *dev,
36 struct cpuidle_driver *drv,
41 set_thread_flag(TIF_POLLING_NRFLAG);
43 pseries_idle_prolog();
45 snooze_exit_time = get_tb() + snooze_timeout;
47 while (!need_resched()) {
50 if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
52 * Task has not woken up but we are exiting the polling
53 * loop anyway. Require a barrier after polling is
54 * cleared to order subsequent test of need_resched().
56 clear_thread_flag(TIF_POLLING_NRFLAG);
63 clear_thread_flag(TIF_POLLING_NRFLAG);
67 pseries_idle_epilog();
72 static void check_and_cede_processor(void)
75 * Ensure our interrupt state is properly tracked,
76 * also checks if no interrupt has occurred while we
79 if (prep_irq_for_idle()) {
81 #ifdef CONFIG_TRACE_IRQFLAGS
82 /* Ensure that H_CEDE returns with IRQs on */
83 if (WARN_ON(!(mfmsr() & MSR_EE)))
89 static int dedicated_cede_loop(struct cpuidle_device *dev,
90 struct cpuidle_driver *drv,
94 pseries_idle_prolog();
95 get_lppaca()->donate_dedicated_cpu = 1;
98 check_and_cede_processor();
101 get_lppaca()->donate_dedicated_cpu = 0;
103 pseries_idle_epilog();
108 static int shared_cede_loop(struct cpuidle_device *dev,
109 struct cpuidle_driver *drv,
113 pseries_idle_prolog();
116 * Yield the processor to the hypervisor. We return if
117 * an external interrupt occurs (which are driven prior
118 * to returning here) or if a prod occurs from another
119 * processor. When returning here, external interrupts
122 check_and_cede_processor();
125 pseries_idle_epilog();
131 * States for dedicated partition case.
133 static struct cpuidle_state dedicated_states[] = {
138 .target_residency = 0,
139 .enter = &snooze_loop },
144 .target_residency = 100,
145 .enter = &dedicated_cede_loop },
149 * States for shared partition case.
151 static struct cpuidle_state shared_states[] = {
156 .target_residency = 0,
157 .enter = &snooze_loop },
159 .name = "Shared Cede",
160 .desc = "Shared Cede",
162 .target_residency = 100,
163 .enter = &shared_cede_loop },
166 static int pseries_cpuidle_cpu_online(unsigned int cpu)
168 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
170 if (dev && cpuidle_get_driver()) {
171 cpuidle_pause_and_lock();
172 cpuidle_enable_device(dev);
173 cpuidle_resume_and_unlock();
178 static int pseries_cpuidle_cpu_dead(unsigned int cpu)
180 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
182 if (dev && cpuidle_get_driver()) {
183 cpuidle_pause_and_lock();
184 cpuidle_disable_device(dev);
185 cpuidle_resume_and_unlock();
191 * pseries_cpuidle_driver_init()
193 static int pseries_cpuidle_driver_init(void)
196 struct cpuidle_driver *drv = &pseries_idle_driver;
198 drv->state_count = 0;
200 for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
201 /* Is the state not enabled? */
202 if (cpuidle_state_table[idle_state].enter == NULL)
205 drv->states[drv->state_count] = /* structure copy */
206 cpuidle_state_table[idle_state];
208 drv->state_count += 1;
215 * pseries_idle_probe()
216 * Choose state table for shared versus dedicated partition
218 static int pseries_idle_probe(void)
221 if (cpuidle_disable != IDLE_NO_OVERRIDE)
224 if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
226 * Use local_paca instead of get_lppaca() since
227 * preemption is not disabled, and it is not required in
228 * fact, since lppaca_ptr does not need to be the value
229 * associated to the current CPU, it can be from any CPU.
231 if (lppaca_shared_proc(local_paca->lppaca_ptr)) {
232 cpuidle_state_table = shared_states;
233 max_idle_state = ARRAY_SIZE(shared_states);
235 cpuidle_state_table = dedicated_states;
236 max_idle_state = ARRAY_SIZE(dedicated_states);
241 if (max_idle_state > 1) {
242 snooze_timeout_en = true;
243 snooze_timeout = cpuidle_state_table[1].target_residency *
249 static int __init pseries_processor_idle_init(void)
253 retval = pseries_idle_probe();
257 pseries_cpuidle_driver_init();
258 retval = cpuidle_register(&pseries_idle_driver, NULL);
260 printk(KERN_DEBUG "Registration of pseries driver failed.\n");
264 retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
265 "cpuidle/pseries:online",
266 pseries_cpuidle_cpu_online, NULL);
268 retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
269 "cpuidle/pseries:DEAD", NULL,
270 pseries_cpuidle_cpu_dead);
272 printk(KERN_DEBUG "pseries_idle_driver registered\n");
276 device_initcall(pseries_processor_idle_init);