drivers/macintosh/windfarm_pid.c

   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
  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
  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
  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
  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");