cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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pid.c (2937B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * pid.c PID controller for testing cooling devices
      4 *
      5 * Copyright (C) 2012 Intel Corporation. All rights reserved.
      6 *
      7 * Author Name Jacob Pan <jacob.jun.pan@linux.intel.com>
      8 */
      9
     10#include <unistd.h>
     11#include <stdio.h>
     12#include <stdlib.h>
     13#include <string.h>
     14#include <stdint.h>
     15#include <sys/types.h>
     16#include <dirent.h>
     17#include <libintl.h>
     18#include <ctype.h>
     19#include <assert.h>
     20#include <time.h>
     21#include <limits.h>
     22#include <math.h>
     23#include <sys/stat.h>
     24#include <syslog.h>
     25
     26#include "tmon.h"
     27
     28/**************************************************************************
     29 * PID (Proportional-Integral-Derivative) controller is commonly used in
     30 * linear control system, consider the the process.
     31 * G(s) = U(s)/E(s)
     32 * kp = proportional gain
     33 * ki = integral gain
     34 * kd = derivative gain
     35 * Ts
     36 * We use type C Alan Bradley equation which takes set point off the
     37 * output dependency in P and D term.
     38 *
     39 *   y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
     40 *          - 2*x[k-1]+x[k-2])/Ts
     41 *
     42 *
     43 ***********************************************************************/
     44struct pid_params p_param;
     45/* cached data from previous loop */
     46static double xk_1, xk_2; /* input temperature x[k-#] */
     47
     48/*
     49 * TODO: make PID parameters tuned automatically,
     50 * 1. use CPU burn to produce open loop unit step response
     51 * 2. calculate PID based on Ziegler-Nichols rule
     52 *
     53 * add a flag for tuning PID
     54 */
     55int init_thermal_controller(void)
     56{
     57
     58	/* init pid params */
     59	p_param.ts = ticktime;
     60	/* TODO: get it from TUI tuning tab */
     61	p_param.kp = .36;
     62	p_param.ki = 5.0;
     63	p_param.kd = 0.19;
     64
     65	p_param.t_target = target_temp_user;
     66
     67	return 0;
     68}
     69
     70void controller_reset(void)
     71{
     72	/* TODO: relax control data when not over thermal limit */
     73	syslog(LOG_DEBUG, "TC inactive, relax p-state\n");
     74	p_param.y_k = 0.0;
     75	xk_1 = 0.0;
     76	xk_2 = 0.0;
     77	set_ctrl_state(0);
     78}
     79
     80/* To be called at time interval Ts. Type C PID controller.
     81 *    y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
     82 *          - 2*x[k-1]+x[k-2])/Ts
     83 * TODO: add low pass filter for D term
     84 */
     85#define GUARD_BAND (2)
     86void controller_handler(const double xk, double *yk)
     87{
     88	double ek;
     89	double p_term, i_term, d_term;
     90
     91	ek = p_param.t_target - xk; /* error */
     92	if (ek >= 3.0) {
     93		syslog(LOG_DEBUG, "PID: %3.1f Below set point %3.1f, stop\n",
     94			xk, p_param.t_target);
     95		controller_reset();
     96		*yk = 0.0;
     97		return;
     98	}
     99	/* compute intermediate PID terms */
    100	p_term = -p_param.kp * (xk - xk_1);
    101	i_term = p_param.kp * p_param.ki * p_param.ts * ek;
    102	d_term = -p_param.kp * p_param.kd * (xk - 2 * xk_1 + xk_2) / p_param.ts;
    103	/* compute output */
    104	*yk += p_term + i_term + d_term;
    105	/* update sample data */
    106	xk_1 = xk;
    107	xk_2 = xk_1;
    108
    109	/* clamp output adjustment range */
    110	if (*yk < -LIMIT_HIGH)
    111		*yk = -LIMIT_HIGH;
    112	else if (*yk > -LIMIT_LOW)
    113		*yk = -LIMIT_LOW;
    114
    115	p_param.y_k = *yk;
    116
    117	set_ctrl_state(lround(fabs(p_param.y_k)));
    118
    119}