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