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1 | /* |
2 | * Windfarm PowerMac thermal control. Generic PID helpers |
3 | * |
4 | * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp. |
5 | * <benh@kernel.crashing.org> |
6 | * |
7 | * Released under the term of the GNU GPL v2. |
8 | */ |
9 | |
10 | #include <linux/types.h> |
11 | #include <linux/errno.h> |
12 | #include <linux/kernel.h> |
13 | #include <linux/string.h> |
14 | #include <linux/module.h> |
15 | |
16 | #include "windfarm_pid.h" |
17 | |
18 | #undef DEBUG |
19 | |
20 | #ifdef DEBUG |
21 | #define DBG(args...) printk(args) |
22 | #else |
23 | #define DBG(args...) do { } while(0) |
24 | #endif |
25 | |
26 | void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param) |
27 | { |
28 | memset(st, 0, sizeof(struct wf_pid_state)); |
29 | st->param = *param; |
30 | st->first = 1; |
31 | } |
32 | EXPORT_SYMBOL_GPL(wf_pid_init); |
33 | |
34 | s32 wf_pid_run(struct wf_pid_state *st, s32 new_sample) |
35 | { |
36 | s64 error, integ, deriv; |
37 | s32 target; |
38 | int i, hlen = st->param.history_len; |
39 | |
40 | /* Calculate error term */ |
41 | error = new_sample - st->param.itarget; |
42 | |
43 | /* Get samples into our history buffer */ |
44 | if (st->first) { |
45 | for (i = 0; i < hlen; i++) { |
46 | st->samples[i] = new_sample; |
47 | st->errors[i] = error; |
48 | } |
49 | st->first = 0; |
50 | st->index = 0; |
51 | } else { |
52 | st->index = (st->index + 1) % hlen; |
53 | st->samples[st->index] = new_sample; |
54 | st->errors[st->index] = error; |
55 | } |
56 | |
57 | /* Calculate integral term */ |
58 | for (i = 0, integ = 0; i < hlen; i++) |
59 | integ += st->errors[(st->index + hlen - i) % hlen]; |
60 | integ *= st->param.interval; |
61 | |
62 | /* Calculate derivative term */ |
63 | deriv = st->errors[st->index] - |
64 | st->errors[(st->index + hlen - 1) % hlen]; |
65 | deriv /= st->param.interval; |
66 | |
67 | /* Calculate target */ |
68 | target = (s32)((integ * (s64)st->param.gr + deriv * (s64)st->param.gd + |
69 | error * (s64)st->param.gp) >> 36); |
70 | if (st->param.additive) |
71 | target += st->target; |
72 | target = max(target, st->param.min); |
73 | target = min(target, st->param.max); |
74 | st->target = target; |
75 | |
76 | return st->target; |
77 | } |
78 | EXPORT_SYMBOL_GPL(wf_pid_run); |
79 | |
80 | void wf_cpu_pid_init(struct wf_cpu_pid_state *st, |
81 | struct wf_cpu_pid_param *param) |
82 | { |
83 | memset(st, 0, sizeof(struct wf_cpu_pid_state)); |
84 | st->param = *param; |
85 | st->first = 1; |
86 | } |
87 | EXPORT_SYMBOL_GPL(wf_cpu_pid_init); |
88 | |
89 | s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 new_power, s32 new_temp) |
90 | { |
91 | s64 integ, deriv, prop; |
92 | s32 error, target, sval, adj; |
93 | int i, hlen = st->param.history_len; |
94 | |
95 | /* Calculate error term */ |
96 | error = st->param.pmaxadj - new_power; |
97 | |
98 | /* Get samples into our history buffer */ |
99 | if (st->first) { |
100 | for (i = 0; i < hlen; i++) { |
101 | st->powers[i] = new_power; |
102 | st->errors[i] = error; |
103 | } |
104 | st->temps[0] = st->temps[1] = new_temp; |
105 | st->first = 0; |
106 | st->index = st->tindex = 0; |
107 | } else { |
108 | st->index = (st->index + 1) % hlen; |
109 | st->powers[st->index] = new_power; |
110 | st->errors[st->index] = error; |
111 | st->tindex = (st->tindex + 1) % 2; |
112 | st->temps[st->tindex] = new_temp; |
113 | } |
114 | |
115 | /* Calculate integral term */ |
116 | for (i = 0, integ = 0; i < hlen; i++) |
117 | integ += st->errors[(st->index + hlen - i) % hlen]; |
118 | integ *= st->param.interval; |
119 | integ *= st->param.gr; |
120 | sval = st->param.tmax - (s32)(integ >> 20); |
121 | adj = min(st->param.ttarget, sval); |
122 | |
123 | DBG("integ: %lx, sval: %lx, adj: %lx\n", integ, sval, adj); |
124 | |
125 | /* Calculate derivative term */ |
126 | deriv = st->temps[st->tindex] - |
127 | st->temps[(st->tindex + 2 - 1) % 2]; |
128 | deriv /= st->param.interval; |
129 | deriv *= st->param.gd; |
130 | |
131 | /* Calculate proportional term */ |
132 | prop = st->last_delta = (new_temp - adj); |
133 | prop *= st->param.gp; |
134 | |
135 | DBG("deriv: %lx, prop: %lx\n", deriv, prop); |
136 | |
137 | /* Calculate target */ |
138 | target = st->target + (s32)((deriv + prop) >> 36); |
139 | target = max(target, st->param.min); |
140 | target = min(target, st->param.max); |
141 | st->target = target; |
142 | |
143 | return st->target; |
144 | } |
145 | EXPORT_SYMBOL_GPL(wf_cpu_pid_run); |
146 | |
147 | MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>"); |
148 | MODULE_DESCRIPTION("PID algorithm for PowerMacs thermal control"); |
149 | MODULE_LICENSE("GPL"); |
150 |
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