cpuidle: Single/Global registration of idle states
[linux-2.6.git] / drivers / cpuidle / governors / ladder.c
1 /*
2  * ladder.c - the residency ladder algorithm
3  *
4  *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
5  *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
6  *  Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
7  *
8  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
9  *               Shaohua Li <shaohua.li@intel.com>
10  *               Adam Belay <abelay@novell.com>
11  *
12  * This code is licenced under the GPL.
13  */
14
15 #include <linux/kernel.h>
16 #include <linux/cpuidle.h>
17 #include <linux/pm_qos_params.h>
18 #include <linux/moduleparam.h>
19 #include <linux/jiffies.h>
20
21 #include <asm/io.h>
22 #include <asm/uaccess.h>
23
24 #define PROMOTION_COUNT 4
25 #define DEMOTION_COUNT 1
26
27 struct ladder_device_state {
28         struct {
29                 u32 promotion_count;
30                 u32 demotion_count;
31                 u32 promotion_time;
32                 u32 demotion_time;
33         } threshold;
34         struct {
35                 int promotion_count;
36                 int demotion_count;
37         } stats;
38 };
39
40 struct ladder_device {
41         struct ladder_device_state states[CPUIDLE_STATE_MAX];
42         int last_state_idx;
43 };
44
45 static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
46
47 /**
48  * ladder_do_selection - prepares private data for a state change
49  * @ldev: the ladder device
50  * @old_idx: the current state index
51  * @new_idx: the new target state index
52  */
53 static inline void ladder_do_selection(struct ladder_device *ldev,
54                                        int old_idx, int new_idx)
55 {
56         ldev->states[old_idx].stats.promotion_count = 0;
57         ldev->states[old_idx].stats.demotion_count = 0;
58         ldev->last_state_idx = new_idx;
59 }
60
61 /**
62  * ladder_select_state - selects the next state to enter
63  * @drv: cpuidle driver
64  * @dev: the CPU
65  */
66 static int ladder_select_state(struct cpuidle_driver *drv,
67                                 struct cpuidle_device *dev)
68 {
69         struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
70         struct ladder_device_state *last_state;
71         int last_residency, last_idx = ldev->last_state_idx;
72         int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
73
74         /* Special case when user has set very strict latency requirement */
75         if (unlikely(latency_req == 0)) {
76                 ladder_do_selection(ldev, last_idx, 0);
77                 return 0;
78         }
79
80         last_state = &ldev->states[last_idx];
81
82         if (drv->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID) {
83                 last_residency = cpuidle_get_last_residency(dev) - \
84                                          drv->states[last_idx].exit_latency;
85         }
86         else
87                 last_residency = last_state->threshold.promotion_time + 1;
88
89         /* consider promotion */
90         if (last_idx < drv->state_count - 1 &&
91             last_residency > last_state->threshold.promotion_time &&
92             drv->states[last_idx + 1].exit_latency <= latency_req) {
93                 last_state->stats.promotion_count++;
94                 last_state->stats.demotion_count = 0;
95                 if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
96                         ladder_do_selection(ldev, last_idx, last_idx + 1);
97                         return last_idx + 1;
98                 }
99         }
100
101         /* consider demotion */
102         if (last_idx > CPUIDLE_DRIVER_STATE_START &&
103             drv->states[last_idx].exit_latency > latency_req) {
104                 int i;
105
106                 for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
107                         if (drv->states[i].exit_latency <= latency_req)
108                                 break;
109                 }
110                 ladder_do_selection(ldev, last_idx, i);
111                 return i;
112         }
113
114         if (last_idx > CPUIDLE_DRIVER_STATE_START &&
115             last_residency < last_state->threshold.demotion_time) {
116                 last_state->stats.demotion_count++;
117                 last_state->stats.promotion_count = 0;
118                 if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
119                         ladder_do_selection(ldev, last_idx, last_idx - 1);
120                         return last_idx - 1;
121                 }
122         }
123
124         /* otherwise remain at the current state */
125         return last_idx;
126 }
127
128 /**
129  * ladder_enable_device - setup for the governor
130  * @drv: cpuidle driver
131  * @dev: the CPU
132  */
133 static int ladder_enable_device(struct cpuidle_driver *drv,
134                                 struct cpuidle_device *dev)
135 {
136         int i;
137         struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
138         struct ladder_device_state *lstate;
139         struct cpuidle_state *state;
140
141         ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
142
143         for (i = 0; i < drv->state_count; i++) {
144                 state = &drv->states[i];
145                 lstate = &ldev->states[i];
146
147                 lstate->stats.promotion_count = 0;
148                 lstate->stats.demotion_count = 0;
149
150                 lstate->threshold.promotion_count = PROMOTION_COUNT;
151                 lstate->threshold.demotion_count = DEMOTION_COUNT;
152
153                 if (i < drv->state_count - 1)
154                         lstate->threshold.promotion_time = state->exit_latency;
155                 if (i > 0)
156                         lstate->threshold.demotion_time = state->exit_latency;
157         }
158
159         return 0;
160 }
161
162 /**
163  * ladder_reflect - update the correct last_state_idx
164  * @dev: the CPU
165  * @index: the index of actual state entered
166  */
167 static void ladder_reflect(struct cpuidle_device *dev, int index)
168 {
169         struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
170         if (index > 0)
171                 ldev->last_state_idx = index;
172 }
173
174 static struct cpuidle_governor ladder_governor = {
175         .name =         "ladder",
176         .rating =       10,
177         .enable =       ladder_enable_device,
178         .select =       ladder_select_state,
179         .reflect =      ladder_reflect,
180         .owner =        THIS_MODULE,
181 };
182
183 /**
184  * init_ladder - initializes the governor
185  */
186 static int __init init_ladder(void)
187 {
188         return cpuidle_register_governor(&ladder_governor);
189 }
190
191 /**
192  * exit_ladder - exits the governor
193  */
194 static void __exit exit_ladder(void)
195 {
196         cpuidle_unregister_governor(&ladder_governor);
197 }
198
199 MODULE_LICENSE("GPL");
200 module_init(init_ladder);
201 module_exit(exit_ladder);