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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> | |
d82b3518 | 17 | #include <linux/pm_qos_params.h> |
4f86d3a8 LB |
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 | * @dev: the CPU | |
64 | */ | |
65 | static 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; | |
ed77134b | 70 | int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); |
4f86d3a8 | 71 | |
a2bd9202 | 72 | /* Special case when user has set very strict latency requirement */ |
73 | if (unlikely(latency_req == 0)) { | |
74 | ladder_do_selection(ldev, last_idx, 0); | |
75 | return 0; | |
76 | } | |
77 | ||
4f86d3a8 LB |
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 | /* consider promotion */ | |
86 | if (last_idx < dev->state_count - 1 && | |
87 | last_residency > last_state->threshold.promotion_time && | |
a2bd9202 | 88 | dev->states[last_idx + 1].exit_latency <= latency_req) { |
4f86d3a8 LB |
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 | /* consider demotion */ | |
06d9e908 | 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 | ||
a2bd9202 | 110 | if (last_idx > CPUIDLE_DRIVER_STATE_START && |
4f86d3a8 LB |
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 | /* otherwise remain at the current state */ | |
121 | return last_idx; | |
122 | } | |
123 | ||
124 | /** | |
125 | * ladder_enable_device - setup for the governor | |
126 | * @dev: the CPU | |
127 | */ | |
128 | static 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 | ||
a2bd9202 | 135 | ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START; |
4f86d3a8 LB |
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 | ||
156 | static 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 | * init_ladder - initializes the governor | |
166 | */ | |
167 | static int __init init_ladder(void) | |
168 | { | |
169 | return cpuidle_register_governor(&ladder_governor); | |
170 | } | |
171 | ||
172 | /** | |
173 | * exit_ladder - exits the governor | |
174 | */ | |
175 | static void __exit exit_ladder(void) | |
176 | { | |
177 | cpuidle_unregister_governor(&ladder_governor); | |
178 | } | |
179 | ||
180 | MODULE_LICENSE("GPL"); | |
181 | module_init(init_ladder); | |
182 | module_exit(exit_ladder); |