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15#include <linux/kernel.h>
16#include <linux/cpuidle.h>
17#include <linux/pm_qos.h>
18#include <linux/module.h>
19#include <linux/jiffies.h>
20#include <linux/tick.h>
21
22#include <asm/io.h>
23#include <asm/uaccess.h>
24
25#define PROMOTION_COUNT 4
26#define DEMOTION_COUNT 1
27
28struct ladder_device_state {
29 struct {
30 u32 promotion_count;
31 u32 demotion_count;
32 u32 promotion_time;
33 u32 demotion_time;
34 } threshold;
35 struct {
36 int promotion_count;
37 int demotion_count;
38 } stats;
39};
40
41struct ladder_device {
42 struct ladder_device_state states[CPUIDLE_STATE_MAX];
43 int last_state_idx;
44};
45
46static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
47
48
49
50
51
52
53
54static inline void ladder_do_selection(struct ladder_device *ldev,
55 int old_idx, int new_idx)
56{
57 ldev->states[old_idx].stats.promotion_count = 0;
58 ldev->states[old_idx].stats.demotion_count = 0;
59 ldev->last_state_idx = new_idx;
60}
61
62
63
64
65
66
67static int ladder_select_state(struct cpuidle_driver *drv,
68 struct cpuidle_device *dev)
69{
70 struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
71 struct ladder_device_state *last_state;
72 int last_residency, last_idx = ldev->last_state_idx;
73 int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
74
75
76 if (unlikely(latency_req == 0)) {
77 ladder_do_selection(ldev, last_idx, 0);
78 return 0;
79 }
80
81 last_state = &ldev->states[last_idx];
82
83 last_residency = cpuidle_get_last_residency(dev) - drv->states[last_idx].exit_latency;
84
85
86 if (last_idx < drv->state_count - 1 &&
87 !drv->states[last_idx + 1].disabled &&
88 !dev->states_usage[last_idx + 1].disable &&
89 last_residency > last_state->threshold.promotion_time &&
90 drv->states[last_idx + 1].exit_latency <= latency_req) {
91 last_state->stats.promotion_count++;
92 last_state->stats.demotion_count = 0;
93 if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
94 ladder_do_selection(ldev, last_idx, last_idx + 1);
95 return last_idx + 1;
96 }
97 }
98
99
100 if (last_idx > CPUIDLE_DRIVER_STATE_START &&
101 (drv->states[last_idx].disabled ||
102 dev->states_usage[last_idx].disable ||
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
125 return last_idx;
126}
127
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130
131
132
133static 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 = CPUIDLE_DRIVER_STATE_START; 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 > CPUIDLE_DRIVER_STATE_START)
156 lstate->threshold.demotion_time = state->exit_latency;
157 }
158
159 return 0;
160}
161
162
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164
165
166
167static void ladder_reflect(struct cpuidle_device *dev, int index)
168{
169 struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
170 if (index > 0)
171 ldev->last_state_idx = index;
172}
173
174static 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
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185
186static int __init init_ladder(void)
187{
188
189
190
191
192
193 if (!tick_nohz_enabled)
194 ladder_governor.rating = 25;
195
196 return cpuidle_register_governor(&ladder_governor);
197}
198
199postcore_initcall(init_ladder);
200
