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

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