1/*
2 *  cpuidle-pseries - idle state cpuidle driver.
3 *  Adapted from drivers/idle/intel_idle.c and
4 *  drivers/acpi/processor_idle.c
5 *
6 */
7
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/moduleparam.h>
12#include <linux/cpuidle.h>
13#include <linux/cpu.h>
14#include <linux/notifier.h>
15
16#include <asm/paca.h>
17#include <asm/reg.h>
18#include <asm/machdep.h>
19#include <asm/firmware.h>
20#include <asm/runlatch.h>
21#include <asm/plpar_wrappers.h>
22
23struct cpuidle_driver pseries_idle_driver = {
24	.name             = "pseries_idle",
25	.owner            = THIS_MODULE,
26};
27
28static int max_idle_state;
29static struct cpuidle_state *cpuidle_state_table;
30
31static inline void idle_loop_prolog(unsigned long *in_purr)
32{
33	ppc64_runlatch_off();
34	*in_purr = mfspr(SPRN_PURR);
35	/*
36	 * Indicate to the HV that we are idle. Now would be
37	 * a good time to find other work to dispatch.
38	 */
39	get_lppaca()->idle = 1;
40}
41
42static inline void idle_loop_epilog(unsigned long in_purr)
43{
44	u64 wait_cycles;
45
46	wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
47	wait_cycles += mfspr(SPRN_PURR) - in_purr;
48	get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
49	get_lppaca()->idle = 0;
50
51	if (irqs_disabled())
52		local_irq_enable();
53	ppc64_runlatch_on();
54}
55
56static int snooze_loop(struct cpuidle_device *dev,
57			struct cpuidle_driver *drv,
58			int index)
59{
60	unsigned long in_purr;
61
62	idle_loop_prolog(&in_purr);
63	local_irq_enable();
64	set_thread_flag(TIF_POLLING_NRFLAG);
65
66	while (!need_resched()) {
67		HMT_low();
68		HMT_very_low();
69	}
70
71	HMT_medium();
72	clear_thread_flag(TIF_POLLING_NRFLAG);
73	smp_mb();
74
75	idle_loop_epilog(in_purr);
76
77	return index;
78}
79
80static void check_and_cede_processor(void)
81{
82	/*
83	 * Ensure our interrupt state is properly tracked,
84	 * also checks if no interrupt has occurred while we
85	 * were soft-disabled
86	 */
87	if (prep_irq_for_idle()) {
88		cede_processor();
89#ifdef CONFIG_TRACE_IRQFLAGS
90		/* Ensure that H_CEDE returns with IRQs on */
91		if (WARN_ON(!(mfmsr() & MSR_EE)))
92			__hard_irq_enable();
93#endif
94	}
95}
96
97static int dedicated_cede_loop(struct cpuidle_device *dev,
98				struct cpuidle_driver *drv,
99				int index)
100{
101	unsigned long in_purr;
102
103	idle_loop_prolog(&in_purr);
104	get_lppaca()->donate_dedicated_cpu = 1;
105
106	HMT_medium();
107	check_and_cede_processor();
108
109	get_lppaca()->donate_dedicated_cpu = 0;
110
111	idle_loop_epilog(in_purr);
112
113	return index;
114}
115
116static int shared_cede_loop(struct cpuidle_device *dev,
117			struct cpuidle_driver *drv,
118			int index)
119{
120	unsigned long in_purr;
121
122	idle_loop_prolog(&in_purr);
123
124	/*
125	 * Yield the processor to the hypervisor.  We return if
126	 * an external interrupt occurs (which are driven prior
127	 * to returning here) or if a prod occurs from another
128	 * processor. When returning here, external interrupts
129	 * are enabled.
130	 */
131	check_and_cede_processor();
132
133	idle_loop_epilog(in_purr);
134
135	return index;
136}
137
138/*
139 * States for dedicated partition case.
140 */
141static struct cpuidle_state dedicated_states[] = {
142	{ /* Snooze */
143		.name = "snooze",
144		.desc = "snooze",
145		.exit_latency = 0,
146		.target_residency = 0,
147		.enter = &snooze_loop },
148	{ /* CEDE */
149		.name = "CEDE",
150		.desc = "CEDE",
151		.exit_latency = 10,
152		.target_residency = 100,
153		.enter = &dedicated_cede_loop },
154};
155
156/*
157 * States for shared partition case.
158 */
159static struct cpuidle_state shared_states[] = {
160	{ /* Shared Cede */
161		.name = "Shared Cede",
162		.desc = "Shared Cede",
163		.exit_latency = 0,
164		.target_residency = 0,
165		.enter = &shared_cede_loop },
166};
167
168static int pseries_cpuidle_add_cpu_notifier(struct notifier_block *n,
169			unsigned long action, void *hcpu)
170{
171	int hotcpu = (unsigned long)hcpu;
172	struct cpuidle_device *dev =
173				per_cpu(cpuidle_devices, hotcpu);
174
175	if (dev && cpuidle_get_driver()) {
176		switch (action) {
177		case CPU_ONLINE:
178		case CPU_ONLINE_FROZEN:
179			cpuidle_pause_and_lock();
180			cpuidle_enable_device(dev);
181			cpuidle_resume_and_unlock();
182			break;
183
184		case CPU_DEAD:
185		case CPU_DEAD_FROZEN:
186			cpuidle_pause_and_lock();
187			cpuidle_disable_device(dev);
188			cpuidle_resume_and_unlock();
189			break;
190
191		default:
192			return NOTIFY_DONE;
193		}
194	}
195	return NOTIFY_OK;
196}
197
198static struct notifier_block setup_hotplug_notifier = {
199	.notifier_call = pseries_cpuidle_add_cpu_notifier,
200};
201
202/*
203 * pseries_cpuidle_driver_init()
204 */
205static int pseries_cpuidle_driver_init(void)
206{
207	int idle_state;
208	struct cpuidle_driver *drv = &pseries_idle_driver;
209
210	drv->state_count = 0;
211
212	for (idle_state = 0; idle_state < max_idle_state; ++idle_state) {
213		/* Is the state not enabled? */
214		if (cpuidle_state_table[idle_state].enter == NULL)
215			continue;
216
217		drv->states[drv->state_count] =	/* structure copy */
218			cpuidle_state_table[idle_state];
219
220		drv->state_count += 1;
221	}
222
223	return 0;
224}
225
226/*
227 * pseries_idle_probe()
228 * Choose state table for shared versus dedicated partition
229 */
230static int pseries_idle_probe(void)
231{
232
233	if (cpuidle_disable != IDLE_NO_OVERRIDE)
234		return -ENODEV;
235
236	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
237		if (lppaca_shared_proc(get_lppaca())) {
238			cpuidle_state_table = shared_states;
239			max_idle_state = ARRAY_SIZE(shared_states);
240		} else {
241			cpuidle_state_table = dedicated_states;
242			max_idle_state = ARRAY_SIZE(dedicated_states);
243		}
244	} else
245		return -ENODEV;
246
247	return 0;
248}
249
250static int __init pseries_processor_idle_init(void)
251{
252	int retval;
253
254	retval = pseries_idle_probe();
255	if (retval)
256		return retval;
257
258	pseries_cpuidle_driver_init();
259	retval = cpuidle_register(&pseries_idle_driver, NULL);
260	if (retval) {
261		printk(KERN_DEBUG "Registration of pseries driver failed.\n");
262		return retval;
263	}
264
265	register_cpu_notifier(&setup_hotplug_notifier);
266	printk(KERN_DEBUG "pseries_idle_driver registered\n");
267	return 0;
268}
269
270device_initcall(pseries_processor_idle_init);
271