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 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
73static 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 */
143struct 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".
150struct xcede_latency_payload {
151	u8     record_size;
152	struct xcede_latency_record records[16];
153} __packed;
154
155struct xcede_latency_parameter {
156	__be16  payload_size;
157	struct xcede_latency_payload payload;
158	u8 null_char;
159} __packed;
160
161static unsigned int nr_xcede_records;
162static struct xcede_latency_parameter xcede_latency_parameter __initdata;
163
164static 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 */
215static u8 cede_latency_hint[NR_DEDICATED_STATES];
216
217static 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
240static 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 */
265static 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 */
283static 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
298static 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
310static 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 */
325static 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
346static void __init fixup_cede0_latency(void)
347{
348	struct xcede_latency_payload *payload;
349	u64 min_latency_us;
350	int i;
351
352	min_latency_us = dedicated_states[1].exit_latency; // CEDE latency
353
354	if (parse_cede_parameters())
355		return;
356
357	pr_info("cpuidle: Skipping the %d Extended CEDE idle states\n",
358		nr_xcede_records);
359
360	payload = &xcede_latency_parameter.payload;
361	for (i = 0; i < nr_xcede_records; i++) {
362		struct xcede_latency_record *record = &payload->records[i];
363		u64 latency_tb = be64_to_cpu(record->latency_ticks);
364		u64 latency_us = DIV_ROUND_UP_ULL(tb_to_ns(latency_tb), NSEC_PER_USEC);
365
366		if (latency_us == 0)
367			pr_warn("cpuidle: xcede record %d has an unrealistic latency of 0us.\n", i);
368
369		if (latency_us < min_latency_us)
370			min_latency_us = latency_us;
371	}
372
373	/*
374	 * By default, we assume that CEDE(0) has exit latency 10us,
375	 * since there is no way for us to query from the platform.
376	 *
377	 * However, if the wakeup latency of an Extended CEDE state is
378	 * smaller than 10us, then we can be sure that CEDE(0)
379	 * requires no more than that.
380	 *
381	 * Perform the fix-up.
382	 */
383	if (min_latency_us < dedicated_states[1].exit_latency) {
384		/*
385		 * We set a minimum of 1us wakeup latency for cede0 to
386		 * distinguish it from snooze
387		 */
388		u64 cede0_latency = 1;
389
390		if (min_latency_us > cede0_latency)
391			cede0_latency = min_latency_us - 1;
392
393		dedicated_states[1].exit_latency = cede0_latency;
394		dedicated_states[1].target_residency = 10 * (cede0_latency);
395		pr_info("cpuidle: Fixed up CEDE exit latency to %llu us\n",
396			cede0_latency);
397	}
398
399}
400
401/*
402 * pseries_idle_probe()
403 * Choose state table for shared versus dedicated partition
404 */
405static int __init pseries_idle_probe(void)
406{
407
408	if (cpuidle_disable != IDLE_NO_OVERRIDE)
409		return -ENODEV;
410
411	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
412		if (lppaca_shared_proc()) {
413			cpuidle_state_table = shared_states;
414			max_idle_state = ARRAY_SIZE(shared_states);
415		} else {
416			/*
417			 * Use firmware provided latency values
418			 * starting with POWER10 platforms. In the
419			 * case that we are running on a POWER10
420			 * platform but in an earlier compat mode, we
421			 * can still use the firmware provided values.
422			 *
423			 * However, on platforms prior to POWER10, we
424			 * cannot rely on the accuracy of the firmware
425			 * provided latency values. On such platforms,
426			 * go with the conservative default estimate
427			 * of 10us.
428			 */
429			if (cpu_has_feature(CPU_FTR_ARCH_31) || pvr_version_is(PVR_POWER10))
430				fixup_cede0_latency();
431			cpuidle_state_table = dedicated_states;
432			max_idle_state = NR_DEDICATED_STATES;
433		}
434	} else
435		return -ENODEV;
436
437	if (max_idle_state > 1) {
438		snooze_timeout_en = true;
439		snooze_timeout = cpuidle_state_table[1].target_residency *
440				 tb_ticks_per_usec;
441	}
442	return 0;
443}
444
445static int __init pseries_processor_idle_init(void)
446{
447	int retval;
448
449	retval = pseries_idle_probe();
450	if (retval)
451		return retval;
452
453	pseries_cpuidle_driver_init();
454	retval = cpuidle_register(&pseries_idle_driver, NULL);
455	if (retval) {
456		printk(KERN_DEBUG "Registration of pseries driver failed.\n");
457		return retval;
458	}
459
460	retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
461					   "cpuidle/pseries:online",
462					   pseries_cpuidle_cpu_online, NULL);
463	WARN_ON(retval < 0);
464	retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
465					   "cpuidle/pseries:DEAD", NULL,
466					   pseries_cpuidle_cpu_dead);
467	WARN_ON(retval < 0);
468	printk(KERN_DEBUG "pseries_idle_driver registered\n");
469	return 0;
470}
471
472device_initcall(pseries_processor_idle_init);
473