Add micro timer interface and a default implementation.

PiperOrigin-RevId: 298971695
Change-Id: I9a532ca7073b55458c5f27e31bcb5869d7221706

tensorflow/lite/micro/BUILD

@@ -81,6 +81,19 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "micro_time",
+    srcs = [
+        "posix/micro_time.cc",
+    ],
+    hdrs = [
+        "micro_time.h",
+    ],
+    build_for_embedded = True,
+    copts = micro_copts(),
+    deps = ["//tensorflow/lite/c:common"],
+)
+
 cc_library(
     name = "micro_utils",
     srcs = [
@@ -196,3 +209,14 @@ tflite_micro_cc_test(
         "//tensorflow/lite/micro/testing:micro_test",
     ],
 )
+
+tflite_micro_cc_test(
+    name = "micro_time_test",
+    srcs = [
+        "micro_time_test.cc",
+    ],
+    deps = [
+        ":micro_time",
+        "//tensorflow/lite/micro/testing:micro_test",
+    ],
+)

tensorflow/lite/micro/micro_time.cc

@@ -0,0 +1,44 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// Reference implementation of timer functions.  Platforms are not required to
+// implement these timer methods, but they are required to enable profiling.
+
+// On platforms that have a POSIX stack or C library, it can be written using
+// methods from <sys/time.h> or clock() from <time.h>.
+
+// To add an equivalent function for your own platform, create your own
+// implementation file, and place it in a subfolder with named after the OS
+// you're targeting. For example, see the Cortex M bare metal version in
+// tensorflow/lite/micro/bluepill/micro_time.cc or the mbed one on
+// tensorflow/lite/micro/mbed/micro_time.cc.
+
+#include "tensorflow/lite/micro/micro_time.h"
+
+namespace tflite {
+
+// Reference implementation of the ticks_per_second() function that's required
+// for a platform to support Tensorflow Lite for Microcontrollers profiling.
+// This returns 0 by default because timing is an optional feature that builds
+// without errors on platforms that do not need it.
+int32_t ticks_per_second() { return 0; }
+
+// Reference implementation of the GetCurrentTimeTicks() function that's
+// required for a platform to support Tensorflow Lite for Microcontrollers
+// profiling. This returns 0 by default because timing is an optional feature
+// that builds without errors on platforms that do not need it.
+int32_t GetCurrentTimeTicks() { return 0; }
+
+}  // namespace tflite

tensorflow/lite/micro/micro_time.h

@@ -0,0 +1,31 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+#ifndef TENSORFLOW_LITE_MICRO_MICRO_TIME_H_
+#define TENSORFLOW_LITE_MICRO_MICRO_TIME_H_
+
+#include <stdint.h>
+
+namespace tflite {
+
+// These functions should be implemented by each target platform, and provide an
+// accurate tick count along with how many ticks there are per second.
+int32_t ticks_per_second();
+
+// Return time in ticks.  The meaning of a tick varies per platform.
+int32_t GetCurrentTimeTicks();
+
+}  // namespace tflite
+
+#endif  // TENSORFLOW_LITE_MICRO_MICRO_TIME_H_

tensorflow/lite/micro/micro_time_test.cc

@@ -0,0 +1,48 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/micro/micro_time.h"
+
+#include "tensorflow/lite/micro/testing/micro_test.h"
+
+TF_LITE_MICRO_TESTS_BEGIN
+
+TF_LITE_MICRO_TEST(TestBasicTimerFunctionality) {
+  int32_t ticks_per_second = tflite::ticks_per_second();
+
+  // Retry enough times to guarantee a tick advance, while not taking too long
+  // to complete.  With 1e6 retries, assuming each loop takes tens of cycles,
+  // this will retry for less than 10 seconds on a 10MHz platform.
+  constexpr int kMaxRetries = 1e6;
+  int start_time = tflite::GetCurrentTimeTicks();
+
+  if (ticks_per_second != 0) {
+    for (int i = 0; i < kMaxRetries; i++) {
+      if (tflite::GetCurrentTimeTicks() - start_time > 0) {
+        break;
+      }
+    }
+  }
+
+  // Ensure the timer is increasing. This works for the overflow case too, since
+  // (MIN_INT + x) - (MAX_INT - y) == x + y + 1.  For example,
+  // 0x80000001(min int + 1) - 0x7FFFFFFE(max int - 1) = 0x00000003 == 3.
+  // GetTicksPerSecond() == 0 means the timer is not implemented on this
+  // platform.
+  TF_LITE_MICRO_EXPECT(ticks_per_second == 0 ||
+                       tflite::GetCurrentTimeTicks() - start_time > 0);
+}
+
+TF_LITE_MICRO_TESTS_END

tensorflow/lite/micro/posix/micro_time.cc

@@ -0,0 +1,28 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// Posix implementation of micro_timer.
+// To include this with make, add TAGS=posix.
+#include "tensorflow/lite/micro/micro_time.h"
+
+#include <time.h>
+
+namespace tflite {
+
+int32_t ticks_per_second() { return CLOCKS_PER_SEC; }
+
+int32_t GetCurrentTimeTicks() { return clock(); }
+
+}  // namespace tflite

tensorflow/lite/micro/sparkfun_edge/micro_time.cc

@@ -0,0 +1,72 @@
+/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// Reference implementation of timer functions.  Platforms are not required to
+// implement these timer methods, but they are required to enable profiling.
+
+// On platforms that have a POSIX stack or C library, it can be written using
+// methods from <sys/time.h> or clock() from <time.h>.
+
+// To add an equivalent function for your own platform, create your own
+// implementation file, and place it in a subfolder with named after the OS
+// you're targeting. For example, see the Cortex M bare metal version in
+// tensorflow/lite/micro/bluepill/micro_timer.cc or the mbed one on
+// tensorflow/lite/micro/mbed/micro_timer.cc.
+
+#include "tensorflow/lite/micro/micro_time.h"
+
+// These are headers from Ambiq's Apollo3 SDK.
+#include "am_bsp.h"         // NOLINT
+#include "am_mcu_apollo.h"  // NOLINT
+#include "am_util.h"        // NOLINT
+
+namespace tflite {
+namespace {
+
+// Select CTIMER 1 as benchmarking timer on Sparkfun Edge. This timer must not
+// be used elsewhere.
+constexpr int kTimerNum = 1;
+
+// Clock set to operate at 12MHz.
+constexpr int kClocksPerSecond = 12e6;
+
+}  // namespace
+
+int32_t ticks_per_second() { return kClocksPerSecond; }
+
+// Calling this method enables a timer that runs for eternity. The user is
+// responsible for avoiding trampling on this timer's config, otherwise timing
+// measurements may no longer be valid.
+int32_t GetCurrentTimeTicks() {
+  // TODO(b/150808076): Split out initialization, intialize in interpreter.
+  static bool is_initialized = false;
+  if (!is_initialized) {
+    am_hal_ctimer_config_t timer_config;
+    // Operate as a 32-bit timer.
+    timer_config.ui32Link = 1;
+    // Set timer A to continuous mode at 12MHz.
+    timer_config.ui32TimerAConfig =
+        AM_HAL_CTIMER_FN_CONTINUOUS | AM_HAL_CTIMER_HFRC_12MHZ;
+
+    am_hal_ctimer_stop(kTimerNum, AM_HAL_CTIMER_BOTH);
+    am_hal_ctimer_clear(kTimerNum, AM_HAL_CTIMER_BOTH);
+    am_hal_ctimer_config(kTimerNum, &timer_config);
+    am_hal_ctimer_start(kTimerNum, AM_HAL_CTIMER_TIMERA);
+    is_initialized = true;
+  }
+  return CTIMERn(kTimerNum)->TMR0;
+}
+
+}  // namespace tflite