[hal,wpilib] Rename FPGA clock to monotonic clock (#8672)

- Remove status return from HAL level (clock getting should never fail)
- Remove 32-bit timestamp expand function
- Make monotonic_clock.hpp (formerly fpga_clock.hpp) header-only and
move to root hal include directory

hal/src/main/java/org/wpilib/hardware/hal/HALUtil.java

@@ -71,11 +71,11 @@ public final class HALUtil extends JNIWrapper {
   public static native int getTeamNumber();
 
   /**
-   * Reads the microsecond-resolution timer on the FPGA.
+   * Reads the microsecond-resolution monotonic timer.
    *
-   * @return The current time in microseconds according to the FPGA (since FPGA reset).
+   * @return The current monotonic time in microseconds.
    */
-  public static native long getFPGATime();
+  public static native long getMonotonicTime();
 
   /**
    * Returns the runtime type of the HAL.

hal/src/main/native/cpp/cpp/fpga_clock.cpp

@@ -1,32 +0,0 @@
-// Copyright (c) FIRST and other WPILib contributors.
-// Open Source Software; you can modify and/or share it under the terms of
-// the WPILib BSD license file in the root directory of this project.
-
-#include "wpi/hal/cpp/fpga_clock.hpp"
-
-#include <cstdio>
-#include <limits>
-
-#include "wpi/hal/HAL.h"
-#include "wpi/util/print.hpp"
-
-namespace wpi::hal {
-const fpga_clock::time_point fpga_clock::min_time =
-    fpga_clock::time_point(fpga_clock::duration(
-        std::numeric_limits<fpga_clock::duration::rep>::min()));
-
-fpga_clock::time_point fpga_clock::now() noexcept {
-  int32_t status = 0;
-  uint64_t currentTime = HAL_GetFPGATime(&status);
-  if (status != 0) {
-    wpi::util::print(
-        stderr,
-        "Call to HAL_GetFPGATime failed in fpga_clock::now() with status {}. "
-        "Initialization might have failed. Time will not be correct\n",
-        status);
-    std::fflush(stderr);
-    return epoch();
-  }
-  return time_point(std::chrono::microseconds(currentTime));
-}
-}  // namespace wpi::hal

hal/src/main/native/cpp/jni/HALUtil.cpp

@@ -473,17 +473,14 @@ Java_org_wpilib_hardware_hal_HALUtil_getTeamNumber
 
 /*
  * Class:     org_wpilib_hardware_hal_HALUtil
- * Method:    getFPGATime
+ * Method:    getMonotonicTime
  * Signature: ()J
  */
 JNIEXPORT jlong JNICALL
-Java_org_wpilib_hardware_hal_HALUtil_getFPGATime
+Java_org_wpilib_hardware_hal_HALUtil_getMonotonicTime
   (JNIEnv* env, jclass)
 {
-  int32_t status = 0;
-  jlong returnValue = HAL_GetFPGATime(&status);
-  CheckStatus(env, status);
-  return returnValue;
+  return HAL_GetMonotonicTime();
 }
 
 /*

hal/src/main/native/include/wpi/hal/HAL.h

@@ -111,29 +111,11 @@ HAL_Bool HAL_GetBrownedOut(int32_t* status);
 int32_t HAL_GetCommsDisableCount(int32_t* status);
 
 /**
- * Reads the microsecond-resolution timer on the FPGA.
+ * Reads the microsecond-resolution monotonic timer.
  *
- * @param[out] status the error code, or 0 for success
- * @return The current time in microseconds according to the FPGA (since FPGA
- * reset).
+ * @return The current monotonic time in microseconds.
  */
-uint64_t HAL_GetFPGATime(int32_t* status);
-
-/**
- * Given an 32 bit FPGA time, expand it to the nearest likely 64 bit FPGA time.
- *
- * Note: This is making the assumption that the timestamp being converted is
- * always in the past.  If you call this with a future timestamp, it probably
- * will make it in the past.  If you wait over 70 minutes between capturing the
- * bottom 32 bits of the timestamp and expanding it, you will be off by
- * multiples of 1<<32 microseconds.
- *
- * @param[in] unexpandedLower 32 bit FPGA time
- * @param[out] status the error code, or 0 for success
- * @return The current time in microseconds according to the FPGA (since FPGA
- *         reset) as a 64 bit number.
- */
-uint64_t HAL_ExpandFPGATime(uint32_t unexpandedLower, int32_t* status);
+uint64_t HAL_GetMonotonicTime(void);
 
 /**
  * Gets the current state of the Robot Signal Light (RSL).

hal/src/main/native/include/wpi/hal/cpp/fpga_clock.hpp

@@ -1,31 +0,0 @@
-// Copyright (c) FIRST and other WPILib contributors.
-// Open Source Software; you can modify and/or share it under the terms of
-// the WPILib BSD license file in the root directory of this project.
-
-#pragma once
-
-#include <chrono>
-
-/** WPILib Hardware Abstraction Layer (HAL) namespace */
-namespace wpi::hal {
-
-/**
- * A std::chrono compatible wrapper around the FPGA Timer.
- */
-class fpga_clock {
- public:
-  using rep = std::chrono::microseconds::rep;
-  using period = std::chrono::microseconds::period;
-  using duration = std::chrono::microseconds;
-  using time_point = std::chrono::time_point<fpga_clock>;
-
-  static fpga_clock::time_point now() noexcept;
-  static constexpr bool is_steady = true;
-
-  static fpga_clock::time_point epoch() noexcept { return time_point(zero()); }
-
-  static fpga_clock::duration zero() noexcept { return duration(0); }
-
-  static const time_point min_time;
-};
-}  // namespace wpi::hal

hal/src/main/native/include/wpi/hal/monotonic_clock.hpp

@@ -0,0 +1,38 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <chrono>
+#include <limits>
+
+#include "wpi/hal/HAL.h"
+
+/** WPILib Hardware Abstraction Layer (HAL) namespace */
+namespace wpi::hal {
+
+/**
+ * A std::chrono compatible wrapper around the HAL monotonic timer.
+ */
+class monotonic_clock {
+ public:
+  using rep = std::chrono::microseconds::rep;
+  using period = std::chrono::microseconds::period;
+  using duration = std::chrono::microseconds;
+  using time_point = std::chrono::time_point<monotonic_clock>;
+
+  static time_point now() noexcept {
+    uint64_t currentTime = HAL_GetMonotonicTime();
+    return time_point(std::chrono::microseconds(currentTime));
+  }
+  static constexpr bool is_steady = true;
+
+  static time_point epoch() noexcept { return time_point(zero()); }
+
+  static duration zero() noexcept { return duration(0); }
+
+  static constexpr time_point min_time =
+      time_point(duration(std::numeric_limits<duration::rep>::min()));
+};
+}  // namespace wpi::hal

hal/src/main/native/sim/Alert.cpp

@@ -75,7 +75,7 @@ void HAL_SetAlertActive(HAL_AlertHandle alertHandle, HAL_Bool active,
       // Already active, do nothing (avoids cost of getting time)
       return;
     }
-    int64_t now = HAL_GetFPGATime(status);
+    int64_t now = HAL_GetMonotonicTime();
     int64_t expected = 0;
     // use compare-exchange to avoid potential race
     alert->activeStartTime.compare_exchange_strong(expected, now);

hal/src/main/native/sim/DriverStation.cpp

@@ -20,7 +20,7 @@
 #include "mockdata/DriverStationDataInternal.hpp"
 #include "wpi/hal/DriverStationTypes.h"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 #include "wpi/hal/simulation/MockHooks.h"
 #include "wpi/util/EventVector.hpp"
 #include "wpi/util/mutex.hpp"
@@ -155,16 +155,16 @@ int32_t HAL_SendError(HAL_Bool isError, int32_t errorCode, HAL_Bool isLVCode,
   static constexpr int KEEP_MSGS = 5;
   std::scoped_lock lock(msgMutex);
   static std::string prevMsg[KEEP_MSGS];
-  static fpga_clock::time_point prevMsgTime[KEEP_MSGS];
+  static monotonic_clock::time_point prevMsgTime[KEEP_MSGS];
   static bool initialized = false;
   if (!initialized) {
     for (int i = 0; i < KEEP_MSGS; i++) {
-      prevMsgTime[i] = fpga_clock::now() - std::chrono::seconds(2);
+      prevMsgTime[i] = monotonic_clock::now() - std::chrono::seconds(2);
     }
     initialized = true;
   }
 
-  auto curTime = fpga_clock::now();
+  auto curTime = monotonic_clock::now();
   int i;
   for (i = 0; i < KEEP_MSGS; ++i) {
     if (prevMsg[i] == details) {

hal/src/main/native/sim/HAL.cpp

@@ -254,32 +254,8 @@ int32_t HAL_GetTeamNumber(void) {
   return HALSIM_GetRoboRioTeamNumber();
 }
 
-uint64_t HAL_GetFPGATime(int32_t* status) {
-  return wpi::hal::GetFPGATime();
-}
-
-uint64_t HAL_ExpandFPGATime(uint32_t unexpandedLower, int32_t* status) {
-  // Capture the current FPGA time.  This will give us the upper half of the
-  // clock.
-  uint64_t fpgaTime = HAL_GetFPGATime(status);
-  if (*status != 0) {
-    return 0;
-  }
-
-  // Now, we need to detect the case where the lower bits rolled over after we
-  // sampled.  In that case, the upper bits will be 1 bigger than they should
-  // be.
-
-  // Break it into lower and upper portions.
-  uint32_t lower = fpgaTime & 0xffffffffull;
-  uint64_t upper = (fpgaTime >> 32) & 0xffffffff;
-
-  // The time was sampled *before* the current time, so roll it back.
-  if (lower < unexpandedLower) {
-    --upper;
-  }
-
-  return (upper << 32) + static_cast<uint64_t>(unexpandedLower);
+uint64_t HAL_GetMonotonicTime(void) {
+  return wpi::hal::GetMonotonicTime();
 }
 
 HAL_Bool HAL_GetSystemActive(int32_t* status) {

hal/src/main/native/sim/MockHooks.cpp

@@ -25,7 +25,7 @@ static std::atomic<uint64_t> programStepTime{0};
 
 namespace wpi::hal::init {
 void InitializeMockHooks() {
-  wpi::util::SetNowImpl(GetFPGATime);
+  wpi::util::SetNowImpl(GetMonotonicTime);
 }
 }  // namespace wpi::hal::init
 
@@ -59,7 +59,7 @@ void StepTiming(uint64_t delta) {
   programStepTime += delta;
 }
 
-uint64_t GetFPGATime() {
+uint64_t GetMonotonicTime() {
   uint64_t curTime = programPauseTime;
   if (curTime == 0) {
     curTime = wpi::util::NowDefault();
@@ -67,10 +67,6 @@ uint64_t GetFPGATime() {
   return curTime + programStepTime - programStartTime;
 }
 
-double GetFPGATimestamp() {
-  return GetFPGATime() * 1.0e-6;
-}
-
 void SetProgramStarted(bool started) {
   programStarted = started;
 }
@@ -131,8 +127,7 @@ void HALSIM_StepTiming(uint64_t delta) {
   WaitNotifiers();
 
   while (delta > 0) {
-    int32_t status = 0;
-    uint64_t curTime = HAL_GetFPGATime(&status);
+    uint64_t curTime = HAL_GetMonotonicTime();
     uint64_t nextTimeout = HALSIM_GetNextNotifierTimeout();
     uint64_t step = (std::min)(delta, nextTimeout - curTime);
 

hal/src/main/native/sim/MockHooksInternal.hpp

@@ -17,9 +17,7 @@ bool IsTimingPaused();
 
 void StepTiming(uint64_t delta);
 
-uint64_t GetFPGATime();
-
-double GetFPGATimestamp();
+uint64_t GetMonotonicTime();
 
 void SetProgramStarted();
 }  // namespace wpi::hal

hal/src/main/native/sim/Notifier.cpp

@@ -93,8 +93,7 @@ void NotifierThread::Main() {
 
     // Wait until next alarm
     const Alarm& alarm = m_alarmQueue.top();
-    int32_t status = 0;
-    uint64_t curTime = HAL_GetFPGATime(&status);
+    uint64_t curTime = HAL_GetMonotonicTime();
     if (alarm.notifier->alarmTime > curTime) {
       m_cond.wait_for(
           lock, std::chrono::microseconds{alarm.notifier->alarmTime - curTime});
@@ -114,8 +113,7 @@ void NotifierThread::Main() {
 
 void NotifierThread::ProcessAlarms(
     wpi::util::SmallVectorImpl<HAL_NotifierHandle>* signaled) {
-  int32_t status = 0;
-  uint64_t curTime = HAL_GetFPGATime(&status);
+  uint64_t curTime = HAL_GetMonotonicTime();
 
   // Process alarms
   while (!m_alarmQueue.empty() &&
@@ -264,7 +262,7 @@ void HAL_SetNotifierAlarm(HAL_NotifierHandle notifierHandle, uint64_t alarmTime,
   }
 
   if (!absolute) {
-    alarmTime += HAL_GetFPGATime(status);
+    alarmTime += HAL_GetMonotonicTime();
   }
 
   uint64_t prevWakeup = UINT64_MAX;

hal/src/main/native/systemcore/AddressableLED.cpp

@@ -20,8 +20,8 @@
 #include "SystemServerInternal.hpp"
 #include "wpi/hal/AddressableLEDTypes.h"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
 #include "wpi/hal/handles/HandlesInternal.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 #include "wpi/nt/NetworkTableInstance.hpp"
 #include "wpi/nt/RawTopic.hpp"
 
@@ -133,9 +133,9 @@ void HAL_FreeAddressableLED(HAL_AddressableLEDHandle handle) {
   smartIoHandles->Free(handle, HAL_HandleEnum::AddressableLED);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("AddressableLED handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/Alert.cpp

@@ -75,7 +75,7 @@ void HAL_SetAlertActive(HAL_AlertHandle alertHandle, HAL_Bool active,
       // Already active, do nothing (avoids cost of getting time)
       return;
     }
-    int64_t now = HAL_GetFPGATime(status);
+    int64_t now = HAL_GetMonotonicTime();
     int64_t expected = 0;
     // use compare-exchange to avoid potential race
     alert->activeStartTime.compare_exchange_strong(expected, now);

hal/src/main/native/systemcore/AnalogInput.cpp

@@ -12,8 +12,8 @@
 #include "PortsInternal.hpp"
 #include "SmartIo.hpp"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
 #include "wpi/hal/handles/HandlesInternal.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 
 namespace wpi::hal::init {
 void InitializeAnalogInput() {}
@@ -73,9 +73,9 @@ void HAL_FreeAnalogInputPort(HAL_AnalogInputHandle analogPortHandle) {
   smartIoHandles->Free(analogPortHandle, HAL_HandleEnum::AnalogInput);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("DIO handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/Counter.cpp

@@ -13,7 +13,7 @@
 #include "HALInternal.hpp"
 #include "PortsInternal.hpp"
 #include "SmartIo.hpp"
-#include "wpi/hal/cpp/fpga_clock.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 
 using namespace wpi::hal;
 
@@ -74,9 +74,9 @@ void HAL_FreeCounter(HAL_CounterHandle counterHandle) {
   smartIoHandles->Free(counterHandle, HAL_HandleEnum::Counter);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("DIO handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/DIO.cpp

@@ -13,8 +13,8 @@
 #include "PortsInternal.hpp"
 #include "SmartIo.hpp"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
 #include "wpi/hal/handles/HandlesInternal.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 
 using namespace wpi::hal;
 
@@ -79,9 +79,9 @@ void HAL_FreeDIOPort(HAL_DigitalHandle dioPortHandle) {
   smartIoHandles->Free(dioPortHandle, HAL_HandleEnum::DIO);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("DIO handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/DutyCycle.cpp

@@ -12,8 +12,8 @@
 #include "PortsInternal.hpp"
 #include "SmartIo.hpp"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
 #include "wpi/hal/handles/HandlesInternal.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 
 using namespace wpi::hal;
 
@@ -71,9 +71,9 @@ void HAL_FreeDutyCycle(HAL_DutyCycleHandle dutyCycleHandle) {
   smartIoHandles->Free(dutyCycleHandle, HAL_HandleEnum::DutyCycle);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("DIO handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/HAL.cpp

@@ -205,35 +205,11 @@ int32_t HAL_GetTeamNumber(void) {
   return teamNumber;
 }
 
-uint64_t HAL_GetFPGATime(int32_t* status) {
+uint64_t HAL_GetMonotonicTime(void) {
   wpi::hal::init::CheckInit();
   return wpi::util::NowDefault();
 }
 
-uint64_t HAL_ExpandFPGATime(uint32_t unexpandedLower, int32_t* status) {
-  // Capture the current FPGA time.  This will give us the upper half of the
-  // clock.
-  uint64_t fpgaTime = HAL_GetFPGATime(status);
-  if (*status != 0) {
-    return 0;
-  }
-
-  // Now, we need to detect the case where the lower bits rolled over after we
-  // sampled.  In that case, the upper bits will be 1 bigger than they should
-  // be.
-
-  // Break it into lower and upper portions.
-  uint32_t lower = fpgaTime & 0xffffffffull;
-  uint64_t upper = (fpgaTime >> 32) & 0xffffffff;
-
-  // The time was sampled *before* the current time, so roll it back.
-  if (lower < unexpandedLower) {
-    --upper;
-  }
-
-  return (upper << 32) + static_cast<uint64_t>(unexpandedLower);
-}
-
 HAL_Bool HAL_GetSystemActive(int32_t* status) {
   wpi::hal::init::CheckInit();
   *status = HAL_HANDLE_ERROR;
@@ -296,14 +272,9 @@ HAL_Bool HAL_Initialize(int32_t timeout, int32_t mode) {
 
   // WPILIB_NetworkCommunication_Reserve(nullptr);
 
-  int32_t status = 0;
-
   wpi::hal::InitializeDriverStation();
 
-  dsStartTime = HAL_GetFPGATime(&status);
-  if (status != 0) {
-    return false;
-  }
+  dsStartTime = HAL_GetMonotonicTime();
 
   wpi::hal::WaitForInitialPacket();
 

hal/src/main/native/systemcore/Notifier.cpp

@@ -84,8 +84,7 @@ void NotifierThread::Main() {
 
     // Wait until next alarm
     const Alarm& alarm = m_alarmQueue.top();
-    int32_t status = 0;
-    uint64_t curTime = HAL_GetFPGATime(&status);
+    uint64_t curTime = HAL_GetMonotonicTime();
     if (alarm.notifier->alarmTime > curTime) {
       m_cond.wait_for(
           lock, std::chrono::microseconds{alarm.notifier->alarmTime - curTime});
@@ -99,8 +98,7 @@ void NotifierThread::Main() {
 }
 
 void NotifierThread::ProcessAlarms() {
-  int32_t status = 0;
-  uint64_t curTime = HAL_GetFPGATime(&status);
+  uint64_t curTime = HAL_GetMonotonicTime();
 
   while (!m_alarmQueue.empty() &&
          m_alarmQueue.top().notifier->alarmTime <= curTime) {
@@ -190,7 +188,7 @@ void HAL_SetNotifierAlarm(HAL_NotifierHandle notifierHandle, uint64_t alarmTime,
   }
 
   if (!absolute) {
-    alarmTime += HAL_GetFPGATime(status);
+    alarmTime += HAL_GetMonotonicTime();
   }
 
   uint64_t prevWakeup = UINT64_MAX;

hal/src/main/native/systemcore/PWM.cpp

@@ -15,8 +15,8 @@
 #include "PortsInternal.hpp"
 #include "SmartIo.hpp"
 #include "wpi/hal/Errors.h"
-#include "wpi/hal/cpp/fpga_clock.hpp"
 #include "wpi/hal/handles/HandlesInternal.hpp"
+#include "wpi/hal/monotonic_clock.hpp"
 
 using namespace wpi::hal;
 
@@ -83,9 +83,9 @@ void HAL_FreePWMPort(HAL_DigitalHandle pwmPortHandle) {
   smartIoHandles->Free(pwmPortHandle, HAL_HandleEnum::PWM);
 
   // Wait for no other object to hold this handle.
-  auto start = wpi::hal::fpga_clock::now();
+  auto start = wpi::hal::monotonic_clock::now();
   while (port.use_count() != 1) {
-    auto current = wpi::hal::fpga_clock::now();
+    auto current = wpi::hal::monotonic_clock::now();
     if (start + std::chrono::seconds(1) < current) {
       std::puts("PWM handle free timeout");
       std::fflush(stdout);

hal/src/main/native/systemcore/PowerDistribution.cpp

@@ -34,10 +34,7 @@ HAL_PowerDistributionHandle HAL_InitializePowerDistribution(
 
     // Ensure we have been alive for long enough to receive a few Power packets.
     do {
-      uint64_t currentTime = HAL_GetFPGATime(status);
-      if (*status != 0) {
-        return HAL_kInvalidHandle;
-      }
+      uint64_t currentTime = HAL_GetMonotonicTime();
       if (currentTime >= waitTime) {
         break;
       }

hal/src/main/python/semiwrap/HAL.yml

@@ -33,8 +33,7 @@ functions:
   HAL_GetRuntimeType:
   HAL_GetSystemActive:
   HAL_GetBrownedOut:
-  HAL_GetFPGATime:
-  HAL_ExpandFPGATime:
+  HAL_GetMonotonicTime:
   HAL_GetRSLState:
   HAL_GetSystemTimeValid:
   HAL_Initialize: