1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Windfarm PowerMac thermal control. Generic PID helpers
4 *
5 * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
6 * <benh@kernel.crashing.org>
7 */
8
9 #include <linux/types.h>
10 #include <linux/errno.h>
11 #include <linux/kernel.h>
12 #include <linux/string.h>
13 #include <linux/module.h>
14
15 #include "windfarm_pid.h"
16
17 #undef DEBUG
18
19 #ifdef DEBUG
20 #define DBG(args...) printk(args)
21 #else
22 #define DBG(args...) do { } while(0)
23 #endif
24
wf_pid_init(struct wf_pid_state * st,struct wf_pid_param * param)25 void wf_pid_init(struct wf_pid_state *st, struct wf_pid_param *param)
26 {
27 memset(st, 0, sizeof(struct wf_pid_state));
28 st->param = *param;
29 st->first = 1;
30 }
31 EXPORT_SYMBOL_GPL(wf_pid_init);
32
wf_pid_run(struct wf_pid_state * st,s32 new_sample)33 s32 wf_pid_run(struct wf_pid_state *st, s32 new_sample)
34 {
35 s64 error, integ, deriv;
36 s32 target;
37 int i, hlen = st->param.history_len;
38
39 /* Calculate error term */
40 error = new_sample - st->param.itarget;
41
42 /* Get samples into our history buffer */
43 if (st->first) {
44 for (i = 0; i < hlen; i++) {
45 st->samples[i] = new_sample;
46 st->errors[i] = error;
47 }
48 st->first = 0;
49 st->index = 0;
50 } else {
51 st->index = (st->index + 1) % hlen;
52 st->samples[st->index] = new_sample;
53 st->errors[st->index] = error;
54 }
55
56 /* Calculate integral term */
57 for (i = 0, integ = 0; i < hlen; i++)
58 integ += st->errors[(st->index + hlen - i) % hlen];
59 integ *= st->param.interval;
60
61 /* Calculate derivative term */
62 deriv = st->errors[st->index] -
63 st->errors[(st->index + hlen - 1) % hlen];
64 deriv /= st->param.interval;
65
66 /* Calculate target */
67 target = (s32)((integ * (s64)st->param.gr + deriv * (s64)st->param.gd +
68 error * (s64)st->param.gp) >> 36);
69 if (st->param.additive)
70 target += st->target;
71 target = max(target, st->param.min);
72 target = min(target, st->param.max);
73 st->target = target;
74
75 return st->target;
76 }
77 EXPORT_SYMBOL_GPL(wf_pid_run);
78
wf_cpu_pid_init(struct wf_cpu_pid_state * st,struct wf_cpu_pid_param * param)79 void wf_cpu_pid_init(struct wf_cpu_pid_state *st,
80 struct wf_cpu_pid_param *param)
81 {
82 memset(st, 0, sizeof(struct wf_cpu_pid_state));
83 st->param = *param;
84 st->first = 1;
85 }
86 EXPORT_SYMBOL_GPL(wf_cpu_pid_init);
87
wf_cpu_pid_run(struct wf_cpu_pid_state * st,s32 new_power,s32 new_temp)88 s32 wf_cpu_pid_run(struct wf_cpu_pid_state *st, s32 new_power, s32 new_temp)
89 {
90 s64 integ, deriv, prop;
91 s32 error, target, sval, adj;
92 int i, hlen = st->param.history_len;
93
94 /* Calculate error term */
95 error = st->param.pmaxadj - new_power;
96
97 /* Get samples into our history buffer */
98 if (st->first) {
99 for (i = 0; i < hlen; i++) {
100 st->powers[i] = new_power;
101 st->errors[i] = error;
102 }
103 st->temps[0] = st->temps[1] = new_temp;
104 st->first = 0;
105 st->index = st->tindex = 0;
106 } else {
107 st->index = (st->index + 1) % hlen;
108 st->powers[st->index] = new_power;
109 st->errors[st->index] = error;
110 st->tindex = (st->tindex + 1) % 2;
111 st->temps[st->tindex] = new_temp;
112 }
113
114 /* Calculate integral term */
115 for (i = 0, integ = 0; i < hlen; i++)
116 integ += st->errors[(st->index + hlen - i) % hlen];
117 integ *= st->param.interval;
118 integ *= st->param.gr;
119 sval = st->param.tmax - (s32)(integ >> 20);
120 adj = min(st->param.ttarget, sval);
121
122 DBG("integ: %lx, sval: %lx, adj: %lx\n", integ, sval, adj);
123
124 /* Calculate derivative term */
125 deriv = st->temps[st->tindex] -
126 st->temps[(st->tindex + 2 - 1) % 2];
127 deriv /= st->param.interval;
128 deriv *= st->param.gd;
129
130 /* Calculate proportional term */
131 prop = st->last_delta = (new_temp - adj);
132 prop *= st->param.gp;
133
134 DBG("deriv: %lx, prop: %lx\n", deriv, prop);
135
136 /* Calculate target */
137 target = st->target + (s32)((deriv + prop) >> 36);
138 target = max(target, st->param.min);
139 target = min(target, st->param.max);
140 st->target = target;
141
142 return st->target;
143 }
144 EXPORT_SYMBOL_GPL(wf_cpu_pid_run);
145
146 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
147 MODULE_DESCRIPTION("PID algorithm for PowerMacs thermal control");
148 MODULE_LICENSE("GPL");
149