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 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 
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 
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 
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 
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 
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 
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  */
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 
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  */
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 
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