1 files changed, 131 insertions, 0 deletions
diff --git a/tools/thermal/tmon/pid.c b/tools/thermal/tmon/pid.c
new file mode 100644
index 00000000000..fd7e9e9d6f4
--- /dev/null
+++ b/tools/thermal/tmon/pid.c
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+/*
+ * pid.c PID controller for testing cooling devices
+ *
+ *
+ *
+ * Copyright (C) 2012 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 or later as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Author Name Jacob Pan <jacob.jun.pan@linux.intel.com>
+ *
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <libintl.h>
+#include <ctype.h>
+#include <assert.h>
+#include <time.h>
+#include <limits.h>
+#include <math.h>
+#include <sys/stat.h>
+#include <syslog.h>
+
+#include "tmon.h"
+
+/**************************************************************************
+ * PID (Proportional-Integral-Derivative) controller is commonly used in
+ * linear control system, consider the the process.
+ * G(s) = U(s)/E(s)
+ * kp = proportional gain
+ * ki = integral gain
+ * kd = derivative gain
+ * Ts
+ * We use type C Alan Bradley equation which takes set point off the
+ * output dependency in P and D term.
+ *
+ *   y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
+ *          - 2*x[k-1]+x[k-2])/Ts
+ *
+ *
+ ***********************************************************************/
+struct pid_params p_param;
+/* cached data from previous loop */
+static double xk_1, xk_2; /* input temperature x[k-#] */
+
+/*
+ * TODO: make PID parameters tuned automatically,
+ * 1. use CPU burn to produce open loop unit step response
+ * 2. calculate PID based on Ziegler-Nichols rule
+ *
+ * add a flag for tuning PID
+ */
+int init_thermal_controller(void)
+{
+	int ret = 0;
+
+	/* init pid params */
+	p_param.ts = ticktime;
+	/* TODO: get it from TUI tuning tab */
+	p_param.kp = .36;
+	p_param.ki = 5.0;
+	p_param.kd = 0.19;
+
+	p_param.t_target = target_temp_user;
+
+	return ret;
+}
+
+void controller_reset(void)
+{
+	/* TODO: relax control data when not over thermal limit */
+	syslog(LOG_DEBUG, "TC inactive, relax p-state\n");
+	p_param.y_k = 0.0;
+	xk_1 = 0.0;
+	xk_2 = 0.0;
+	set_ctrl_state(0);
+}
+
+/* To be called at time interval Ts. Type C PID controller.
+ *    y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
+ *          - 2*x[k-1]+x[k-2])/Ts
+ * TODO: add low pass filter for D term
+ */
+#define GUARD_BAND (2)
+void controller_handler(const double xk, double *yk)
+{
+	double ek;
+	double p_term, i_term, d_term;
+
+	ek = p_param.t_target - xk; /* error */
+	if (ek >= 3.0) {
+		syslog(LOG_DEBUG, "PID: %3.1f Below set point %3.1f, stop\n",
+			xk, p_param.t_target);
+		controller_reset();
+		*yk = 0.0;
+		return;
+	}
+	/* compute intermediate PID terms */
+	p_term = -p_param.kp * (xk - xk_1);
+	i_term = p_param.kp * p_param.ki * p_param.ts * ek;
+	d_term = -p_param.kp * p_param.kd * (xk - 2 * xk_1 + xk_2) / p_param.ts;
+	/* compute output */
+	*yk += p_term + i_term + d_term;
+	/* update sample data */
+	xk_1 = xk;
+	xk_2 = xk_1;
+
+	/* clamp output adjustment range */
+	if (*yk < -LIMIT_HIGH)
+		*yk = -LIMIT_HIGH;
+	else if (*yk > -LIMIT_LOW)
+		*yk = -LIMIT_LOW;
+
+	p_param.y_k = *yk;
+
+	set_ctrl_state(lround(fabs(p_param.y_k)));
+
+}