Add cycle counter driver and test app

Author: hudson-ayers

examples/tests/cycle_count/Makefile

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+# Makefile for user application
+
+# Specify this directory relative to the current application.
+TOCK_USERLAND_BASE_DIR = ../../..
+
+# Which files to compile.
+C_SRCS := $(wildcard *.c)
+
+# Include userland master makefile. Contains rules and flags for actually
+# building the application.
+include $(TOCK_USERLAND_BASE_DIR)/AppMakefile.mk

examples/tests/cycle_count/README.md

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+Test `cycle_count`
+====================
+
+This tests the cycle counter capsule.
+It will print the number of cycles required to toggle an LED.

examples/tests/cycle_count/main.c

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+#include <stdio.h>
+
+#include <cycle_counter.h>
+#include <led.h>
+#include <tock.h>
+
+int main(void) {
+  uint64_t cycles = 0;
+
+  int rc = cycle_counter_reset();
+  if (rc == RETURNCODE_ENOSUPPORT) {
+    printf("Cycle counter not available\n");
+  } else if (rc == RETURNCODE_ERESERVE) {
+    printf("Cycle counter claimed by another app\n");
+  } else if (rc != 0) {
+    printf("Cycle counter: other error: %d\n", rc);
+  }
+
+  if (rc != 0) {
+    return 0;
+  }
+
+  cycle_counter_start();
+  led_toggle(0);
+  cycle_counter_stop();
+  cycle_counter_read(&cycles);
+  printf("cycles to toggle led first time: %d\n", cycles);
+
+  cycle_counter_reset();
+  cycle_counter_start();
+  led_toggle(0);
+  cycle_counter_stop();
+  cycle_counter_read(&cycles);
+  printf("cycles to toggle led second time: %d\n", cycles);
+  return 0;
+}

libtock/cycle_counter.c

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+#include "cycle_counter.h"
+
+bool cycle_counter_exists(void) {
+  return driver_exists(DRIVER_NUM_CYCLE_COUNTER);
+}
+
+// Start the cycle counter
+int cycle_counter_start(void) {
+  syscall_return_t rval = command(DRIVER_NUM_CYCLE_COUNTER, 1, 0, 0);
+  return tock_command_return_novalue_to_returncode(rval);
+}
+
+// Get the current cycle count
+int cycle_counter_read(uint64_t* count) {
+  syscall_return_t rval = command(DRIVER_NUM_CYCLE_COUNTER, 2, 0, 0);
+  return tock_command_return_u64_to_returncode(rval, (uint64_t*) count);
+}
+
+// Reset the cycle counter
+int cycle_counter_reset(void) {
+  syscall_return_t rval = command(DRIVER_NUM_CYCLE_COUNTER, 3, 0, 0);
+  return tock_command_return_novalue_to_returncode(rval);
+}
+
+// Stop the cycle counter
+int cycle_counter_stop(void) {
+  syscall_return_t rval = command(DRIVER_NUM_CYCLE_COUNTER, 4, 0, 0);
+  return tock_command_return_novalue_to_returncode(rval);
+}

libtock/cycle_counter.h

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+#pragma once
+
+#include "tock.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define DRIVER_NUM_CYCLE_COUNTER 0x00090008
+
+bool cycle_counter_exists(void);
+int cycle_counter_start(void);
+int cycle_counter_stop(void);
+int cycle_counter_reset(void);
+int cycle_counter_read(int *count);
+
+#ifdef __cplusplus
+}
+#endif