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

source code of linux/drivers/cpuidle/cpuidle-pseries.c