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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Windfarm PowerMac thermal control. Generic PID helpers4 *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 DEBUG18 19#ifdef DEBUG20#define DBG(args...) printk(args)21#else22#define DBG(args...) do { } while(0)23#endif24 25void 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}31EXPORT_SYMBOL_GPL(wf_pid_init);32 33s32 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}77EXPORT_SYMBOL_GPL(wf_pid_run);78 79void 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}86EXPORT_SYMBOL_GPL(wf_cpu_pid_init);87 88s32 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}144EXPORT_SYMBOL_GPL(wf_cpu_pid_run);145 146MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");147MODULE_DESCRIPTION("PID algorithm for PowerMacs thermal control");148MODULE_LICENSE("GPL");149