summaryrefslogtreecommitdiffstats
path: root/drivers/cpuidle/cpuidle-pseries.c
blob: 74c247972bb363e6cf952773ad86b9a48b26b19d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
// SPDX-License-Identifier: GPL-2.0
/*
 *  cpuidle-pseries - idle state cpuidle driver.
 *  Adapted from drivers/idle/intel_idle.c and
 *  drivers/acpi/processor_idle.c
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
#include <linux/notifier.h>

#include <asm/paca.h>
#include <asm/reg.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/runlatch.h>
#include <asm/plpar_wrappers.h>

struct cpuidle_driver pseries_idle_driver = {
	.name             = "pseries_idle",
	.owner            = THIS_MODULE,
};

static int max_idle_state __read_mostly;
static struct cpuidle_state *cpuidle_state_table __read_mostly;
static u64 snooze_timeout __read_mostly;
static bool snooze_timeout_en __read_mostly;

static inline void idle_loop_prolog(unsigned long *in_purr)
{
	ppc64_runlatch_off();
	*in_purr = mfspr(SPRN_PURR);
	/*
	 * Indicate to the HV that we are idle. Now would be
	 * a good time to find other work to dispatch.
	 */
	get_lppaca()->idle = 1;
}

static inline void idle_loop_epilog(unsigned long in_purr)
{
	u64 wait_cycles;

	wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
	wait_cycles += mfspr(SPRN_PURR) - in_purr;
	get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
	get_lppaca()->idle = 0;

	ppc64_runlatch_on();
}

static int snooze_loop(struct cpuidle_device *dev,
			struct cpuidle_driver *drv,
			int index)
{
	unsigned long in_purr;
	u64 snooze_exit_time;

	set_thread_flag(TIF_POLLING_NRFLAG);

	idle_loop_prolog(&in_purr);
	local_irq_enable();
	snooze_exit_time = get_tb() + snooze_timeout;

	while (!need_resched()) {
		HMT_low();
		HMT_very_low();
		if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) {
			/*
			 * Task has not woken up but we are exiting the polling
			 * loop anyway. Require a barrier after polling is
			 * cleared to order subsequent test of need_resched().
			 */
			clear_thread_flag(TIF_POLLING_NRFLAG);
			smp_mb();
			break;
		}
	}

	HMT_medium();
	clear_thread_flag(TIF_POLLING_NRFLAG);

	local_irq_disable();

	idle_loop_epilog(in_purr);

	return index;
}

static void check_and_cede_processor(void)
{
	/*
	 * Ensure our interrupt state is properly tracked,
	 * also checks if no interrupt has occurred while we
	 * were soft-disabled
	 */
	if (prep_irq_for_idle()) {
		cede_processor();
#ifdef CONFIG_TRACE_IRQFLAGS
		/* Ensure that H_CEDE returns with IRQs on */
		if (WARN_ON(!(mfmsr() & MSR_EE)))
			__hard_irq_enable();
#endif
	}
}

static int dedicated_cede_loop(struct cpuidle_device *dev,
				struct cpuidle_driver *drv,
				int index)
{
	unsigned long in_purr;

	idle_loop_prolog(&in_purr);
	get_lppaca()->donate_dedicated_cpu = 1;

	HMT_medium();
	check_and_cede_processor();

	local_irq_disable();
	get_lppaca()->donate_dedicated_cpu = 0;

	idle_loop_epilog(in_purr);

	return index;
}

static int shared_cede_loop(struct cpuidle_device *dev,
			struct cpuidle_driver *drv,
			int index)
{
	unsigned long in_purr;

	idle_loop_prolog(&in_purr);

	/*
	 * Yield the processor to the hypervisor.  We return if
	 * an external interrupt occurs (which are driven prior
	 * to returning here) or if a prod occurs from another
	 * processor. When returning here, external interrupts
	 * are enabled.
	 */
	check_and_cede_processor();

	local_irq_disable();
	idle_loop_epilog(in_purr);

	return index;
}

/*
 * States for dedicated partition case.
 */
static struct cpuidle_state dedicated_states[] = {
	{ /* Snooze */
		.name = "snooze",
		.desc = "snooze",
		.exit_latency = 0,
		.target_residency = 0,
		.enter = &snooze_loop },
	{ /* CEDE */
		.name = "CEDE",
		.desc = "CEDE",
		.exit_latency = 10,
		.target_residency = 100,
		.enter = &dedicated_cede_loop },
};

/*
 * States for shared partition case.
 */
static struct cpuidle_state shared_states[] = {
	{ /* Snooze */
		.name = "snooze",
		.desc = "snooze",
		.exit_latency = 0,
		.target_residency = 0,
		.enter = &snooze_loop },
	{ /* Shared Cede */
		.name = "Shared Cede",
		.desc = "Shared Cede",
		.exit_latency = 10,
		.target_residency = 100,
		.enter = &shared_cede_loop },
};

static int pseries_cpuidle_cpu_online(unsigned int cpu)
{
	struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);

	if (dev && cpuidle_get_driver()) {
		cpuidle_pause_and_lock();
		cpuidle_enable_device(dev);
		cpuidle_resume_and_unlock();
	}
	return 0;
}

static int pseries_cpuidle_cpu_dead(unsigned int cpu)
{
	struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);

	if (dev && cpuidle_get_driver()) {
		cpuidle_pause_and_lock();
		cpuidle_disable_device(dev);
		cpuidle_resume_and_unlock();
	}
	return 0;
}

/*
 * pseries_cpuidle_driver_init()
 */
static int pseries_cpuidle_driver_init(void)
{
	int idle_state;
	struct cpuidle_driver *drv = &pseries_idle_driver;

	drv->state_count = 0;

	for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
		/* Is the state not enabled? */
		if (cpuidle_state_table[idle_state].enter == NULL)
			continue;

		drv->states[drv->state_count] =	/* structure copy */
			cpuidle_state_table[idle_state];

		drv->state_count += 1;
	}

	return 0;
}

/*
 * pseries_idle_probe()
 * Choose state table for shared versus dedicated partition
 */
static int pseries_idle_probe(void)
{

	if (cpuidle_disable != IDLE_NO_OVERRIDE)
		return -ENODEV;

	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
		/*
		 * Use local_paca instead of get_lppaca() since
		 * preemption is not disabled, and it is not required in
		 * fact, since lppaca_ptr does not need to be the value
		 * associated to the current CPU, it can be from any CPU.
		 */
		if (lppaca_shared_proc(local_paca->lppaca_ptr)) {
			cpuidle_state_table = shared_states;
			max_idle_state = ARRAY_SIZE(shared_states);
		} else {
			cpuidle_state_table = dedicated_states;
			max_idle_state = ARRAY_SIZE(dedicated_states);
		}
	} else
		return -ENODEV;

	if (max_idle_state > 1) {
		snooze_timeout_en = true;
		snooze_timeout = cpuidle_state_table[1].target_residency *
				 tb_ticks_per_usec;
	}
	return 0;
}

static int __init pseries_processor_idle_init(void)
{
	int retval;

	retval = pseries_idle_probe();
	if (retval)
		return retval;

	pseries_cpuidle_driver_init();
	retval = cpuidle_register(&pseries_idle_driver, NULL);
	if (retval) {
		printk(KERN_DEBUG "Registration of pseries driver failed.\n");
		return retval;
	}

	retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
					   "cpuidle/pseries:online",
					   pseries_cpuidle_cpu_online, NULL);
	WARN_ON(retval < 0);
	retval = cpuhp_setup_state_nocalls(CPUHP_CPUIDLE_DEAD,
					   "cpuidle/pseries:DEAD", NULL,
					   pseries_cpuidle_cpu_dead);
	WARN_ON(retval < 0);
	printk(KERN_DEBUG "pseries_idle_driver registered\n");
	return 0;
}

device_initcall(pseries_processor_idle_init);