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4f86d3a8 LB |
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> | |
e8db0be1 | 17 | #include <linux/pm_qos.h> |
70e522a0 | 18 | #include <linux/module.h> |
4f86d3a8 | 19 | #include <linux/jiffies.h> |
66a5f6b6 | 20 | #include <linux/tick.h> |
4f86d3a8 LB |
21 | |
22 | #include <asm/io.h> | |
23 | #include <asm/uaccess.h> | |
24 | ||
25 | #define PROMOTION_COUNT 4 | |
26 | #define DEMOTION_COUNT 1 | |
27 | ||
28 | struct 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 | ||
41 | struct ladder_device { | |
42 | struct ladder_device_state states[CPUIDLE_STATE_MAX]; | |
43 | int last_state_idx; | |
44 | }; | |
45 | ||
46 | static DEFINE_PER_CPU(struct ladder_device, ladder_devices); | |
47 | ||
48 | /** | |
49 | * ladder_do_selection - prepares private data for a state change | |
50 | * @ldev: the ladder device | |
51 | * @old_idx: the current state index | |
52 | * @new_idx: the new target state index | |
53 | */ | |
54 | static 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 | * ladder_select_state - selects the next state to enter | |
46bcfad7 | 64 | * @drv: cpuidle driver |
4f86d3a8 LB |
65 | * @dev: the CPU |
66 | */ | |
46bcfad7 DD |
67 | static int ladder_select_state(struct cpuidle_driver *drv, |
68 | struct cpuidle_device *dev) | |
4f86d3a8 | 69 | { |
229b6863 | 70 | struct ladder_device *ldev = this_cpu_ptr(&ladder_devices); |
4f86d3a8 LB |
71 | struct ladder_device_state *last_state; |
72 | int last_residency, last_idx = ldev->last_state_idx; | |
ed77134b | 73 | int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); |
4f86d3a8 | 74 | |
a2bd9202 | 75 | /* Special case when user has set very strict latency requirement */ |
76 | if (unlikely(latency_req == 0)) { | |
77 | ladder_do_selection(ldev, last_idx, 0); | |
78 | return 0; | |
79 | } | |
80 | ||
4f86d3a8 LB |
81 | last_state = &ldev->states[last_idx]; |
82 | ||
b73026b9 | 83 | last_residency = cpuidle_get_last_residency(dev) - drv->states[last_idx].exit_latency; |
4f86d3a8 LB |
84 | |
85 | /* consider promotion */ | |
46bcfad7 | 86 | if (last_idx < drv->state_count - 1 && |
66804c13 | 87 | !drv->states[last_idx + 1].disabled && |
62d6ae88 | 88 | !dev->states_usage[last_idx + 1].disable && |
4f86d3a8 | 89 | last_residency > last_state->threshold.promotion_time && |
46bcfad7 | 90 | drv->states[last_idx + 1].exit_latency <= latency_req) { |
4f86d3a8 LB |
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 | /* consider demotion */ | |
06d9e908 | 100 | if (last_idx > CPUIDLE_DRIVER_STATE_START && |
66804c13 RW |
101 | (drv->states[last_idx].disabled || |
102 | dev->states_usage[last_idx].disable || | |
62d6ae88 | 103 | drv->states[last_idx].exit_latency > latency_req)) { |
06d9e908 | 104 | int i; |
105 | ||
106 | for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) { | |
46bcfad7 | 107 | if (drv->states[i].exit_latency <= latency_req) |
06d9e908 | 108 | break; |
109 | } | |
110 | ladder_do_selection(ldev, last_idx, i); | |
111 | return i; | |
112 | } | |
113 | ||
a2bd9202 | 114 | if (last_idx > CPUIDLE_DRIVER_STATE_START && |
4f86d3a8 LB |
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 | |
46bcfad7 | 130 | * @drv: cpuidle driver |
4f86d3a8 LB |
131 | * @dev: the CPU |
132 | */ | |
46bcfad7 DD |
133 | static int ladder_enable_device(struct cpuidle_driver *drv, |
134 | struct cpuidle_device *dev) | |
4f86d3a8 LB |
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 | ||
a2bd9202 | 141 | ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START; |
4f86d3a8 | 142 | |
14692446 | 143 | for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) { |
46bcfad7 | 144 | state = &drv->states[i]; |
4f86d3a8 LB |
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 | ||
46bcfad7 | 153 | if (i < drv->state_count - 1) |
4f86d3a8 | 154 | lstate->threshold.promotion_time = state->exit_latency; |
14692446 | 155 | if (i > CPUIDLE_DRIVER_STATE_START) |
4f86d3a8 LB |
156 | lstate->threshold.demotion_time = state->exit_latency; |
157 | } | |
158 | ||
159 | return 0; | |
160 | } | |
161 | ||
e978aa7d DD |
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 | { | |
229b6863 | 169 | struct ladder_device *ldev = this_cpu_ptr(&ladder_devices); |
e978aa7d DD |
170 | if (index > 0) |
171 | ldev->last_state_idx = index; | |
172 | } | |
173 | ||
4f86d3a8 LB |
174 | static struct cpuidle_governor ladder_governor = { |
175 | .name = "ladder", | |
176 | .rating = 10, | |
177 | .enable = ladder_enable_device, | |
178 | .select = ladder_select_state, | |
e978aa7d | 179 | .reflect = ladder_reflect, |
4f86d3a8 LB |
180 | .owner = THIS_MODULE, |
181 | }; | |
182 | ||
183 | /** | |
184 | * init_ladder - initializes the governor | |
185 | */ | |
186 | static int __init init_ladder(void) | |
187 | { | |
66a5f6b6 JD |
188 | /* |
189 | * When NO_HZ is disabled, or when booting with nohz=off, the ladder | |
190 | * governor is better so give it a higher rating than the menu | |
191 | * governor. | |
192 | */ | |
193 | if (!tick_nohz_enabled) | |
194 | ladder_governor.rating = 25; | |
195 | ||
4f86d3a8 LB |
196 | return cpuidle_register_governor(&ladder_governor); |
197 | } | |
198 | ||
137b944e | 199 | postcore_initcall(init_ladder); |