1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * cpuidle-pseries - idle state cpuidle driver.
4 * Adapted from drivers/idle/intel_idle.c and
5 * drivers/acpi/processor_idle.c
6 *
7 */
8
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>
16
17 #include <asm/paca.h>
18 #include <asm/reg.h>
19 #include <asm/machdep.h>
20 #include <asm/firmware.h>
21 #include <asm/runlatch.h>
22 #include <asm/plpar_wrappers.h>
23
24 struct cpuidle_driver pseries_idle_driver = {
25 .name = "pseries_idle",
26 .owner = THIS_MODULE,
27 };
28
29 static int max_idle_state __read_mostly;
30 static struct cpuidle_state *cpuidle_state_table __read_mostly;
31 static u64 snooze_timeout __read_mostly;
32 static bool snooze_timeout_en __read_mostly;
33
idle_loop_prolog(unsigned long * in_purr)34 static inline void idle_loop_prolog(unsigned long *in_purr)
35 {
36 ppc64_runlatch_off();
37 *in_purr = mfspr(SPRN_PURR);
38 /*
39 * Indicate to the HV that we are idle. Now would be
40 * a good time to find other work to dispatch.
41 */
42 get_lppaca()->idle = 1;
43 }
44
idle_loop_epilog(unsigned long in_purr)45 static inline void idle_loop_epilog(unsigned long in_purr)
46 {
47 u64 wait_cycles;
48
49 wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
50 wait_cycles += mfspr(SPRN_PURR) - in_purr;
51 get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
52 get_lppaca()->idle = 0;
53
54 ppc64_runlatch_on();
55 }
56
snooze_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)57 static int snooze_loop(struct cpuidle_device *dev,
58 struct cpuidle_driver *drv,
59 int index)
60 {
61 unsigned long in_purr;
62 u64 snooze_exit_time;
63
64 set_thread_flag(TIF_POLLING_NRFLAG);
65
66 idle_loop_prolog(&in_purr);
67 local_irq_enable();
68 snooze_exit_time = get_tb() + snooze_timeout;
69
70 while (!need_resched()) {
71 HMT_low();
72 HMT_very_low();
73 if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
74 /*
75 * Task has not woken up but we are exiting the polling
76 * loop anyway. Require a barrier after polling is
77 * cleared to order subsequent test of need_resched().
78 */
79 clear_thread_flag(TIF_POLLING_NRFLAG);
80 smp_mb();
81 break;
82 }
83 }
84
85 HMT_medium();
86 clear_thread_flag(TIF_POLLING_NRFLAG);
87
88 local_irq_disable();
89
90 idle_loop_epilog(in_purr);
91
92 return index;
93 }
94
check_and_cede_processor(void)95 static void check_and_cede_processor(void)
96 {
97 /*
98 * Ensure our interrupt state is properly tracked,
99 * also checks if no interrupt has occurred while we
100 * were soft-disabled
101 */
102 if (prep_irq_for_idle()) {
103 cede_processor();
104 #ifdef CONFIG_TRACE_IRQFLAGS
105 /* Ensure that H_CEDE returns with IRQs on */
106 if (WARN_ON(!(mfmsr() & MSR_EE)))
107 __hard_irq_enable();
108 #endif
109 }
110 }
111
dedicated_cede_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)112 static int dedicated_cede_loop(struct cpuidle_device *dev,
113 struct cpuidle_driver *drv,
114 int index)
115 {
116 unsigned long in_purr;
117
118 idle_loop_prolog(&in_purr);
119 get_lppaca()->donate_dedicated_cpu = 1;
120
121 HMT_medium();
122 check_and_cede_processor();
123
124 local_irq_disable();
125 get_lppaca()->donate_dedicated_cpu = 0;
126
127 idle_loop_epilog(in_purr);
128
129 return index;
130 }
131
shared_cede_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)132 static int shared_cede_loop(struct cpuidle_device *dev,
133 struct cpuidle_driver *drv,
134 int index)
135 {
136 unsigned long in_purr;
137
138 idle_loop_prolog(&in_purr);
139
140 /*
141 * Yield the processor to the hypervisor. We return if
142 * an external interrupt occurs (which are driven prior
143 * to returning here) or if a prod occurs from another
144 * processor. When returning here, external interrupts
145 * are enabled.
146 */
147 check_and_cede_processor();
148
149 local_irq_disable();
150 idle_loop_epilog(in_purr);
151
152 return index;
153 }
154
155 /*
156 * States for dedicated partition case.
157 */
158 static struct cpuidle_state dedicated_states[] = {
159 { /* Snooze */
160 .name = "snooze",
161 .desc = "snooze",
162 .exit_latency = 0,
163 .target_residency = 0,
164 .enter = &snooze_loop },
165 { /* CEDE */
166 .name = "CEDE",
167 .desc = "CEDE",
168 .exit_latency = 10,
169 .target_residency = 100,
170 .enter = &dedicated_cede_loop },
171 };
172
173 /*
174 * States for shared partition case.
175 */
176 static struct cpuidle_state shared_states[] = {
177 { /* Snooze */
178 .name = "snooze",
179 .desc = "snooze",
180 .exit_latency = 0,
181 .target_residency = 0,
182 .enter = &snooze_loop },
183 { /* Shared Cede */
184 .name = "Shared Cede",
185 .desc = "Shared Cede",
186 .exit_latency = 10,
187 .target_residency = 100,
188 .enter = &shared_cede_loop },
189 };
190
pseries_cpuidle_cpu_online(unsigned int cpu)191 static int pseries_cpuidle_cpu_online(unsigned int cpu)
192 {
193 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
194
195 if (dev && cpuidle_get_driver()) {
196 cpuidle_pause_and_lock();
197 cpuidle_enable_device(dev);
198 cpuidle_resume_and_unlock();
199 }
200 return 0;
201 }
202
pseries_cpuidle_cpu_dead(unsigned int cpu)203 static int pseries_cpuidle_cpu_dead(unsigned int cpu)
204 {
205 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
206
207 if (dev && cpuidle_get_driver()) {
208 cpuidle_pause_and_lock();
209 cpuidle_disable_device(dev);
210 cpuidle_resume_and_unlock();
211 }
212 return 0;
213 }
214
215 /*
216 * pseries_cpuidle_driver_init()
217 */
pseries_cpuidle_driver_init(void)218 static int pseries_cpuidle_driver_init(void)
219 {
220 int idle_state;
221 struct cpuidle_driver *drv = &pseries_idle_driver;
222
223 drv->state_count = 0;
224
225 for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
226 /* Is the state not enabled? */
227 if (cpuidle_state_table[idle_state].enter == NULL)
228 continue;
229
230 drv->states[drv->state_count] = /* structure copy */
231 cpuidle_state_table[idle_state];
232
233 drv->state_count += 1;
234 }
235
236 return 0;
237 }
238
239 /*
240 * pseries_idle_probe()
241 * Choose state table for shared versus dedicated partition
242 */
pseries_idle_probe(void)243 static int pseries_idle_probe(void)
244 {
245
246 if (cpuidle_disable != IDLE_NO_OVERRIDE)
247 return -ENODEV;
248
249 if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
250 /*
251 * Use local_paca instead of get_lppaca() since
252 * preemption is not disabled, and it is not required in
253 * fact, since lppaca_ptr does not need to be the value
254 * associated to the current CPU, it can be from any CPU.
255 */
256 if (lppaca_shared_proc(local_paca->lppaca_ptr)) {
257 cpuidle_state_table = shared_states;
258 max_idle_state = ARRAY_SIZE(shared_states);
259 } else {
260 cpuidle_state_table = dedicated_states;
261 max_idle_state = ARRAY_SIZE(dedicated_states);
262 }
263 } else
264 return -ENODEV;
265
266 if (max_idle_state > 1) {
267 snooze_timeout_en = true;
268 snooze_timeout = cpuidle_state_table[1].target_residency *
269 tb_ticks_per_usec;
270 }
271 return 0;
272 }
273
pseries_processor_idle_init(void)274 static int __init pseries_processor_idle_init(void)
275 {
276 int retval;
277
278 retval = pseries_idle_probe();
279 if (retval)
280 return retval;
281
282 pseries_cpuidle_driver_init();
283 retval = cpuidle_register(&pseries_idle_driver, NULL);
284 if (retval) {
285 printk(KERN_DEBUG "Registration of pseries driver failed.\n");
286 return retval;
287 }
288
289 retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
290 "cpuidle/pseries:online",
291 pseries_cpuidle_cpu_online, NULL);
292 WARN_ON(retval < 0);
293 retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
294 "cpuidle/pseries:DEAD", NULL,
295 pseries_cpuidle_cpu_dead);
296 WARN_ON(retval < 0);
297 printk(KERN_DEBUG "pseries_idle_driver registered\n");
298 return 0;
299 }
300
301 device_initcall(pseries_processor_idle_init);
302