nvidia-gpu: add energy sensor

This commit introduces a energy sensor for the GPU.

Tested: Build an image for gb200nvl-obmc machine with the following
patches cherry picked. This patches are needed to enable the mctp stack.

https://gerrit.openbmc.org/c/openbmc/openbmc/+/79422

```
$ curl -s -k -u 'root:0penBmc' https://10.137.203.137/redfish/v1/Chassis/NVIDIA_GB200_1/Sensors/energy_NVIDIA_GB200_GPU_0_Energy_0
{
  "@odata.id": "/redfish/v1/Chassis/NVIDIA_GB200_1/Sensors/energy_NVIDIA_GB200_GPU_0_Energy_0",
  "@odata.type": "#Sensor.v1_2_0.Sensor",
  "Id": "energy_NVIDIA_GB200_GPU_0_Energy_0",
  "Name": "NVIDIA GB200 GPU 0 Energy 0",
  "Reading": 269947.856,
  "ReadingRangeMax": 1.8446744073709552e+16,
  "ReadingRangeMin": 0.0,
  "ReadingType": "EnergyJoules",
  "ReadingUnits": "J",
  "Status": {
    "Health": "OK",
    "State": "Enabled"
  }
}%
```

Change-Id: I6f53ab2a83eedd54005bbdcd781dc8d320d7f26a
Signed-off-by: Harshit Aghera <haghera@nvidia.com>
diff --git a/src/nvidia-gpu/NvidiaGpuEnergySensor.cpp b/src/nvidia-gpu/NvidiaGpuEnergySensor.cpp
new file mode 100644
index 0000000..6d0fcd8
--- /dev/null
+++ b/src/nvidia-gpu/NvidiaGpuEnergySensor.cpp
@@ -0,0 +1,129 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION &
+ * AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "NvidiaGpuEnergySensor.hpp"
+
+#include "SensorPaths.hpp"
+#include "Thresholds.hpp"
+#include "Utils.hpp"
+#include "sensor.hpp"
+
+#include <bits/basic_string.h>
+
+#include <MctpRequester.hpp>
+#include <NvidiaDeviceDiscovery.hpp>
+#include <NvidiaGpuMctpVdm.hpp>
+#include <OcpMctpVdm.hpp>
+#include <phosphor-logging/lg2.hpp>
+#include <sdbusplus/asio/connection.hpp>
+#include <sdbusplus/asio/object_server.hpp>
+
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+using namespace std::literals;
+
+// Reading from the device is in millijoules and unit set on the dbus is Joules.
+static constexpr double gpuEnergySensorMaxReading =
+    std::numeric_limits<uint64_t>::max() / 1000.0;
+static constexpr double gpuEnergySensorMinReading = 0.0;
+
+NvidiaGpuEnergySensor::NvidiaGpuEnergySensor(
+    std::shared_ptr<sdbusplus::asio::connection>& conn,
+    mctp::MctpRequester& mctpRequester, const std::string& name,
+    const std::string& sensorConfiguration, const uint8_t eid, uint8_t sensorId,
+    sdbusplus::asio::object_server& objectServer,
+    std::vector<thresholds::Threshold>&& thresholdData) :
+    Sensor(escapeName(name), std::move(thresholdData), sensorConfiguration,
+           "energy", false, true, gpuEnergySensorMaxReading,
+           gpuEnergySensorMinReading, conn),
+    eid(eid), sensorId{sensorId}, mctpRequester(mctpRequester),
+    objectServer(objectServer)
+{
+    std::string dbusPath = sensorPathPrefix + "energy/"s + escapeName(name);
+
+    sensorInterface = objectServer.add_interface(
+        dbusPath, "xyz.openbmc_project.Sensor.Value");
+
+    for (const auto& threshold : thresholds)
+    {
+        std::string interface = thresholds::getInterface(threshold.level);
+        thresholdInterfaces[static_cast<size_t>(threshold.level)] =
+            objectServer.add_interface(dbusPath, interface);
+    }
+
+    association = objectServer.add_interface(dbusPath, association::interface);
+
+    setInitialProperties(sensor_paths::unitJoules);
+}
+
+NvidiaGpuEnergySensor::~NvidiaGpuEnergySensor()
+{
+    for (const auto& iface : thresholdInterfaces)
+    {
+        objectServer.remove_interface(iface);
+    }
+    objectServer.remove_interface(sensorInterface);
+    objectServer.remove_interface(association);
+}
+
+void NvidiaGpuEnergySensor::checkThresholds()
+{
+    thresholds::checkThresholds(this);
+}
+
+void NvidiaGpuEnergySensor::processResponse(int sendRecvMsgResult)
+{
+    if (sendRecvMsgResult != 0)
+    {
+        lg2::error(
+            "Error updating Energy Sensor for eid {EID} and sensor id {SID} : sending message over MCTP failed, rc={RC}",
+            "EID", eid, "SID", sensorId, "RC", sendRecvMsgResult);
+        return;
+    }
+
+    ocp::accelerator_management::CompletionCode cc{};
+    uint16_t reasonCode = 0;
+    uint64_t energyValue = 0;
+
+    auto rc = gpu::decodeGetCurrentEnergyCounterResponse(
+        response, cc, reasonCode, energyValue);
+
+    if (rc != 0 || cc != ocp::accelerator_management::CompletionCode::SUCCESS)
+    {
+        lg2::error(
+            "Error updating Energy Sensor for eid {EID} and sensor id {SID} : decode failed, rc={RC}, cc={CC}, reasonCode={RESC}",
+            "EID", eid, "SID", sensorId, "RC", rc, "CC", cc, "RESC",
+            reasonCode);
+        return;
+    }
+
+    // Reading from the device is in millijoules and unit set on the dbus
+    // is Joules.
+    updateValue(energyValue / 1000.0);
+}
+
+void NvidiaGpuEnergySensor::update()
+{
+    auto rc = gpu::encodeGetCurrentEnergyCounterRequest(0, sensorId, request);
+
+    if (rc != 0)
+    {
+        lg2::error(
+            "Error updating Energy Sensor for eid {EID} and sensor id {SID} : encode failed, rc={RC}",
+            "EID", eid, "SID", sensorId, "RC", rc);
+        return;
+    }
+
+    mctpRequester.sendRecvMsg(
+        eid, request, response,
+        [this](int sendRecvMsgResult) { processResponse(sendRecvMsgResult); });
+}