tools/thermal: Introduce tmon, a tool for thermal subsystem

Increasingly, Linux is running on thermally constrained devices. The simple
thermal relationship between processor and fan has become past for modern
computers.

As hardware vendors cope with the thermal constraints on their products,
more sensors are added, new cooling capabilities are introduced. The
complexity of the thermal relationship can grow exponentially among cooling
devices, zones, sensors, and trip points. They can also change dynamically.

To expose such relationship to the userspace, Linux generic thermal layer
introduced sysfs entry at /sys/class/thermal with a matrix of symbolic
links, trip point bindings, and device instances. To traverse such
matrix by hand is not a trivial task. Testing is also difficult in that
thermal conditions are often exception cases that hard to reach in
normal operations.

TMON is conceived as a tool to help visualize, tune, and test the
complex thermal subsystem.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

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 000000000000..fd7e9e9d6f4a
--- /dev/null
+++ b/tools/thermal/tmon/pid.c
@@ -0,0 +1,131 @@
+/*
+ * 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)));
+
+}