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/idle.h>
23 #include <asm/plpar_wrappers.h>
24 #include <asm/rtas.h>
25
26 static struct cpuidle_driver pseries_idle_driver = {
27 .name = "pseries_idle",
28 .owner = THIS_MODULE,
29 };
30
31 static int max_idle_state __read_mostly;
32 static struct cpuidle_state *cpuidle_state_table __read_mostly;
33 static u64 snooze_timeout __read_mostly;
34 static bool snooze_timeout_en __read_mostly;
35
snooze_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)36 static int snooze_loop(struct cpuidle_device *dev,
37 struct cpuidle_driver *drv,
38 int index)
39 {
40 u64 snooze_exit_time;
41
42 set_thread_flag(TIF_POLLING_NRFLAG);
43
44 pseries_idle_prolog();
45 local_irq_enable();
46 snooze_exit_time = get_tb() + snooze_timeout;
47
48 while (!need_resched()) {
49 HMT_low();
50 HMT_very_low();
51 if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
52 /*
53 * Task has not woken up but we are exiting the polling
54 * loop anyway. Require a barrier after polling is
55 * cleared to order subsequent test of need_resched().
56 */
57 clear_thread_flag(TIF_POLLING_NRFLAG);
58 smp_mb();
59 break;
60 }
61 }
62
63 HMT_medium();
64 clear_thread_flag(TIF_POLLING_NRFLAG);
65
66 local_irq_disable();
67
68 pseries_idle_epilog();
69
70 return index;
71 }
72
check_and_cede_processor(void)73 static void check_and_cede_processor(void)
74 {
75 /*
76 * Ensure our interrupt state is properly tracked,
77 * also checks if no interrupt has occurred while we
78 * were soft-disabled
79 */
80 if (prep_irq_for_idle()) {
81 cede_processor();
82 #ifdef CONFIG_TRACE_IRQFLAGS
83 /* Ensure that H_CEDE returns with IRQs on */
84 if (WARN_ON(!(mfmsr() & MSR_EE)))
85 __hard_irq_enable();
86 #endif
87 }
88 }
89
90 /*
91 * XCEDE: Extended CEDE states discovered through the
92 * "ibm,get-systems-parameter" RTAS call with the token
93 * CEDE_LATENCY_TOKEN
94 */
95
96 /*
97 * Section 7.3.16 System Parameters Option of PAPR version 2.8.1 has a
98 * table with all the parameters to ibm,get-system-parameters.
99 * CEDE_LATENCY_TOKEN corresponds to the token value for Cede Latency
100 * Settings Information.
101 */
102 #define CEDE_LATENCY_TOKEN 45
103
104 /*
105 * If the platform supports the cede latency settings information system
106 * parameter it must provide the following information in the NULL terminated
107 * parameter string:
108 *
109 * a. The first byte is the length “N” of each cede latency setting record minus
110 * one (zero indicates a length of 1 byte).
111 *
112 * b. For each supported cede latency setting a cede latency setting record
113 * consisting of the first “N” bytes as per the following table.
114 *
115 * -----------------------------
116 * | Field | Field |
117 * | Name | Length |
118 * -----------------------------
119 * | Cede Latency | 1 Byte |
120 * | Specifier Value | |
121 * -----------------------------
122 * | Maximum wakeup | |
123 * | latency in | 8 Bytes |
124 * | tb-ticks | |
125 * -----------------------------
126 * | Responsive to | |
127 * | external | 1 Byte |
128 * | interrupts | |
129 * -----------------------------
130 *
131 * This version has cede latency record size = 10.
132 *
133 * The structure xcede_latency_payload represents a) and b) with
134 * xcede_latency_record representing the table in b).
135 *
136 * xcede_latency_parameter is what gets returned by
137 * ibm,get-systems-parameter RTAS call when made with
138 * CEDE_LATENCY_TOKEN.
139 *
140 * These structures are only used to represent the data obtained by the RTAS
141 * call. The data is in big-endian.
142 */
143 struct xcede_latency_record {
144 u8 hint;
145 __be64 latency_ticks;
146 u8 wake_on_irqs;
147 } __packed;
148
149 // Make space for 16 records, which "should be enough".
150 struct xcede_latency_payload {
151 u8 record_size;
152 struct xcede_latency_record records[16];
153 } __packed;
154
155 struct xcede_latency_parameter {
156 __be16 payload_size;
157 struct xcede_latency_payload payload;
158 u8 null_char;
159 } __packed;
160
161 static unsigned int nr_xcede_records;
162 static struct xcede_latency_parameter xcede_latency_parameter __initdata;
163
parse_cede_parameters(void)164 static int __init parse_cede_parameters(void)
165 {
166 struct xcede_latency_payload *payload;
167 u32 total_xcede_records_size;
168 u8 xcede_record_size;
169 u16 payload_size;
170 int ret, i;
171
172 ret = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
173 NULL, CEDE_LATENCY_TOKEN, __pa(&xcede_latency_parameter),
174 sizeof(xcede_latency_parameter));
175 if (ret) {
176 pr_err("xcede: Error parsing CEDE_LATENCY_TOKEN\n");
177 return ret;
178 }
179
180 payload_size = be16_to_cpu(xcede_latency_parameter.payload_size);
181 payload = &xcede_latency_parameter.payload;
182
183 xcede_record_size = payload->record_size + 1;
184
185 if (xcede_record_size != sizeof(struct xcede_latency_record)) {
186 pr_err("xcede: Expected record-size %lu. Observed size %u.\n",
187 sizeof(struct xcede_latency_record), xcede_record_size);
188 return -EINVAL;
189 }
190
191 pr_info("xcede: xcede_record_size = %d\n", xcede_record_size);
192
193 /*
194 * Since the payload_size includes the last NULL byte and the
195 * xcede_record_size, the remaining bytes correspond to array of all
196 * cede_latency settings.
197 */
198 total_xcede_records_size = payload_size - 2;
199 nr_xcede_records = total_xcede_records_size / xcede_record_size;
200
201 for (i = 0; i < nr_xcede_records; i++) {
202 struct xcede_latency_record *record = &payload->records[i];
203 u64 latency_ticks = be64_to_cpu(record->latency_ticks);
204 u8 wake_on_irqs = record->wake_on_irqs;
205 u8 hint = record->hint;
206
207 pr_info("xcede: Record %d : hint = %u, latency = 0x%llx tb ticks, Wake-on-irq = %u\n",
208 i, hint, latency_ticks, wake_on_irqs);
209 }
210
211 return 0;
212 }
213
214 #define NR_DEDICATED_STATES 2 /* snooze, CEDE */
215 static u8 cede_latency_hint[NR_DEDICATED_STATES];
216
dedicated_cede_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)217 static int dedicated_cede_loop(struct cpuidle_device *dev,
218 struct cpuidle_driver *drv,
219 int index)
220 {
221 u8 old_latency_hint;
222
223 pseries_idle_prolog();
224 get_lppaca()->donate_dedicated_cpu = 1;
225 old_latency_hint = get_lppaca()->cede_latency_hint;
226 get_lppaca()->cede_latency_hint = cede_latency_hint[index];
227
228 HMT_medium();
229 check_and_cede_processor();
230
231 local_irq_disable();
232 get_lppaca()->donate_dedicated_cpu = 0;
233 get_lppaca()->cede_latency_hint = old_latency_hint;
234
235 pseries_idle_epilog();
236
237 return index;
238 }
239
shared_cede_loop(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)240 static int shared_cede_loop(struct cpuidle_device *dev,
241 struct cpuidle_driver *drv,
242 int index)
243 {
244
245 pseries_idle_prolog();
246
247 /*
248 * Yield the processor to the hypervisor. We return if
249 * an external interrupt occurs (which are driven prior
250 * to returning here) or if a prod occurs from another
251 * processor. When returning here, external interrupts
252 * are enabled.
253 */
254 check_and_cede_processor();
255
256 local_irq_disable();
257 pseries_idle_epilog();
258
259 return index;
260 }
261
262 /*
263 * States for dedicated partition case.
264 */
265 static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = {
266 { /* Snooze */
267 .name = "snooze",
268 .desc = "snooze",
269 .exit_latency = 0,
270 .target_residency = 0,
271 .enter = &snooze_loop },
272 { /* CEDE */
273 .name = "CEDE",
274 .desc = "CEDE",
275 .exit_latency = 10,
276 .target_residency = 100,
277 .enter = &dedicated_cede_loop },
278 };
279
280 /*
281 * States for shared partition case.
282 */
283 static struct cpuidle_state shared_states[] = {
284 { /* Snooze */
285 .name = "snooze",
286 .desc = "snooze",
287 .exit_latency = 0,
288 .target_residency = 0,
289 .enter = &snooze_loop },
290 { /* Shared Cede */
291 .name = "Shared Cede",
292 .desc = "Shared Cede",
293 .exit_latency = 10,
294 .target_residency = 100,
295 .enter = &shared_cede_loop },
296 };
297
pseries_cpuidle_cpu_online(unsigned int cpu)298 static int pseries_cpuidle_cpu_online(unsigned int cpu)
299 {
300 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
301
302 if (dev && cpuidle_get_driver()) {
303 cpuidle_pause_and_lock();
304 cpuidle_enable_device(dev);
305 cpuidle_resume_and_unlock();
306 }
307 return 0;
308 }
309
pseries_cpuidle_cpu_dead(unsigned int cpu)310 static int pseries_cpuidle_cpu_dead(unsigned int cpu)
311 {
312 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
313
314 if (dev && cpuidle_get_driver()) {
315 cpuidle_pause_and_lock();
316 cpuidle_disable_device(dev);
317 cpuidle_resume_and_unlock();
318 }
319 return 0;
320 }
321
322 /*
323 * pseries_cpuidle_driver_init()
324 */
pseries_cpuidle_driver_init(void)325 static int pseries_cpuidle_driver_init(void)
326 {
327 int idle_state;
328 struct cpuidle_driver *drv = &pseries_idle_driver;
329
330 drv->state_count = 0;
331
332 for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
333 /* Is the state not enabled? */
334 if (cpuidle_state_table[idle_state].enter == NULL)
335 continue;
336
337 drv->states[drv->state_count] = /* structure copy */
338 cpuidle_state_table[idle_state];
339
340 drv->state_count += 1;
341 }
342
343 return 0;
344 }
345
fixup_cede0_latency(void)346 static void __init fixup_cede0_latency(void)
347 {
348 struct xcede_latency_payload *payload;
349 u64 min_xcede_latency_us = UINT_MAX;
350 int i;
351
352 if (parse_cede_parameters())
353 return;
354
355 pr_info("cpuidle: Skipping the %d Extended CEDE idle states\n",
356 nr_xcede_records);
357
358 payload = &xcede_latency_parameter.payload;
359
360 /*
361 * The CEDE idle state maps to CEDE(0). While the hypervisor
362 * does not advertise CEDE(0) exit latency values, it does
363 * advertise the latency values of the extended CEDE states.
364 * We use the lowest advertised exit latency value as a proxy
365 * for the exit latency of CEDE(0).
366 */
367 for (i = 0; i < nr_xcede_records; i++) {
368 struct xcede_latency_record *record = &payload->records[i];
369 u8 hint = record->hint;
370 u64 latency_tb = be64_to_cpu(record->latency_ticks);
371 u64 latency_us = DIV_ROUND_UP_ULL(tb_to_ns(latency_tb), NSEC_PER_USEC);
372
373 /*
374 * We expect the exit latency of an extended CEDE
375 * state to be non-zero, it to since it takes at least
376 * a few nanoseconds to wakeup the idle CPU and
377 * dispatch the virtual processor into the Linux
378 * Guest.
379 *
380 * So we consider only non-zero value for performing
381 * the fixup of CEDE(0) latency.
382 */
383 if (latency_us == 0) {
384 pr_warn("cpuidle: Skipping xcede record %d [hint=%d]. Exit latency = 0us\n",
385 i, hint);
386 continue;
387 }
388
389 if (latency_us < min_xcede_latency_us)
390 min_xcede_latency_us = latency_us;
391 }
392
393 if (min_xcede_latency_us != UINT_MAX) {
394 dedicated_states[1].exit_latency = min_xcede_latency_us;
395 dedicated_states[1].target_residency = 10 * (min_xcede_latency_us);
396 pr_info("cpuidle: Fixed up CEDE exit latency to %llu us\n",
397 min_xcede_latency_us);
398 }
399
400 }
401
402 /*
403 * pseries_idle_probe()
404 * Choose state table for shared versus dedicated partition
405 */
pseries_idle_probe(void)406 static int __init pseries_idle_probe(void)
407 {
408
409 if (cpuidle_disable != IDLE_NO_OVERRIDE)
410 return -ENODEV;
411
412 if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
413 /*
414 * Use local_paca instead of get_lppaca() since
415 * preemption is not disabled, and it is not required in
416 * fact, since lppaca_ptr does not need to be the value
417 * associated to the current CPU, it can be from any CPU.
418 */
419 if (lppaca_shared_proc(local_paca->lppaca_ptr)) {
420 cpuidle_state_table = shared_states;
421 max_idle_state = ARRAY_SIZE(shared_states);
422 } else {
423 /*
424 * Use firmware provided latency values
425 * starting with POWER10 platforms. In the
426 * case that we are running on a POWER10
427 * platform but in an earlier compat mode, we
428 * can still use the firmware provided values.
429 *
430 * However, on platforms prior to POWER10, we
431 * cannot rely on the accuracy of the firmware
432 * provided latency values. On such platforms,
433 * go with the conservative default estimate
434 * of 10us.
435 */
436 if (cpu_has_feature(CPU_FTR_ARCH_31) || pvr_version_is(PVR_POWER10))
437 fixup_cede0_latency();
438 cpuidle_state_table = dedicated_states;
439 max_idle_state = NR_DEDICATED_STATES;
440 }
441 } else
442 return -ENODEV;
443
444 if (max_idle_state > 1) {
445 snooze_timeout_en = true;
446 snooze_timeout = cpuidle_state_table[1].target_residency *
447 tb_ticks_per_usec;
448 }
449 return 0;
450 }
451
pseries_processor_idle_init(void)452 static int __init pseries_processor_idle_init(void)
453 {
454 int retval;
455
456 retval = pseries_idle_probe();
457 if (retval)
458 return retval;
459
460 pseries_cpuidle_driver_init();
461 retval = cpuidle_register(&pseries_idle_driver, NULL);
462 if (retval) {
463 printk(KERN_DEBUG "Registration of pseries driver failed.\n");
464 return retval;
465 }
466
467 retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
468 "cpuidle/pseries:online",
469 pseries_cpuidle_cpu_online, NULL);
470 WARN_ON(retval < 0);
471 retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
472 "cpuidle/pseries:DEAD", NULL,
473 pseries_cpuidle_cpu_dead);
474 WARN_ON(retval < 0);
475 printk(KERN_DEBUG "pseries_idle_driver registered\n");
476 return 0;
477 }
478
479 device_initcall(pseries_processor_idle_init);
480