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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
27struct 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
40struct ladder_device {
41 struct ladder_device_state states[CPUIDLE_STATE_MAX];
42 int last_state_idx;
43};
44
45static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
46
47
48
49
50
51
52
53static 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
63
64
65static int ladder_select_state(struct cpuidle_device *dev)
66{
67 struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
68 struct ladder_device_state *last_state;
69 int last_residency, last_idx = ldev->last_state_idx;
70 int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
71
72
73 if (unlikely(latency_req == 0)) {
74 ladder_do_selection(ldev, last_idx, 0);
75 return 0;
76 }
77
78 last_state = &ldev->states[last_idx];
79
80 if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID)
81 last_residency = cpuidle_get_last_residency(dev) - dev->states[last_idx].exit_latency;
82 else
83 last_residency = last_state->threshold.promotion_time + 1;
84
85
86 if (last_idx < dev->state_count - 1 &&
87 last_residency > last_state->threshold.promotion_time &&
88 dev->states[last_idx + 1].exit_latency <= latency_req) {
89 last_state->stats.promotion_count++;
90 last_state->stats.demotion_count = 0;
91 if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
92 ladder_do_selection(ldev, last_idx, last_idx + 1);
93 return last_idx + 1;
94 }
95 }
96
97
98 if (last_idx > CPUIDLE_DRIVER_STATE_START &&
99 dev->states[last_idx].exit_latency > latency_req) {
100 int i;
101
102 for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
103 if (dev->states[i].exit_latency <= latency_req)
104 break;
105 }
106 ladder_do_selection(ldev, last_idx, i);
107 return i;
108 }
109
110 if (last_idx > CPUIDLE_DRIVER_STATE_START &&
111 last_residency < last_state->threshold.demotion_time) {
112 last_state->stats.demotion_count++;
113 last_state->stats.promotion_count = 0;
114 if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
115 ladder_do_selection(ldev, last_idx, last_idx - 1);
116 return last_idx - 1;
117 }
118 }
119
120
121 return last_idx;
122}
123
124
125
126
127
128static int ladder_enable_device(struct cpuidle_device *dev)
129{
130 int i;
131 struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
132 struct ladder_device_state *lstate;
133 struct cpuidle_state *state;
134
135 ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
136
137 for (i = 0; i < dev->state_count; i++) {
138 state = &dev->states[i];
139 lstate = &ldev->states[i];
140
141 lstate->stats.promotion_count = 0;
142 lstate->stats.demotion_count = 0;
143
144 lstate->threshold.promotion_count = PROMOTION_COUNT;
145 lstate->threshold.demotion_count = DEMOTION_COUNT;
146
147 if (i < dev->state_count - 1)
148 lstate->threshold.promotion_time = state->exit_latency;
149 if (i > 0)
150 lstate->threshold.demotion_time = state->exit_latency;
151 }
152
153 return 0;
154}
155
156static struct cpuidle_governor ladder_governor = {
157 .name = "ladder",
158 .rating = 10,
159 .enable = ladder_enable_device,
160 .select = ladder_select_state,
161 .owner = THIS_MODULE,
162};
163
164
165
166
167static int __init init_ladder(void)
168{
169 return cpuidle_register_governor(&ladder_governor);
170}
171
172
173
174
175static void __exit exit_ladder(void)
176{
177 cpuidle_unregister_governor(&ladder_governor);
178}
179
180MODULE_LICENSE("GPL");
181module_init(init_ladder);
182module_exit(exit_ladder);
183
