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 
36 static __cpuidle
37 int 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 
75 static __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  */
145 struct 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".
152 struct xcede_latency_payload {
153 	u8     record_size;
154 	struct xcede_latency_record records[16];
155 } __packed;
156 
157 struct xcede_latency_parameter {
158 	__be16  payload_size;
159 	struct xcede_latency_payload payload;
160 	u8 null_char;
161 } __packed;
162 
163 static unsigned int nr_xcede_records;
164 static struct xcede_latency_parameter xcede_latency_parameter __initdata;
165 
166 static 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 */
217 static u8 cede_latency_hint[NR_DEDICATED_STATES];
218 
219 static __cpuidle
220 int 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 
242 static __cpuidle
243 int 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  */
267 static 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  */
286 static 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 
302 static 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 
314 static 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  */
329 static 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 
350 static 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  */
410 static 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 
450 static 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(&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(CPUHP_AP_ONLINE_DYN,
466 					   "cpuidle/pseries:online",
467 					   pseries_cpuidle_cpu_online, NULL);
468 	WARN_ON(retval < 0);
469 	retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
470 					   "cpuidle/pseries:DEAD", NULL,
471 					   pseries_cpuidle_cpu_dead);
472 	WARN_ON(retval < 0);
473 	printk(KERN_DEBUG "pseries_idle_driver registered\n");
474 	return 0;
475 }
476 
477 device_initcall(pseries_processor_idle_init);
478