chpp/platform/aoc/chpp_uart_link_manager.cc

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * 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 "chpp/platform/chpp_uart_link_manager.h"

#include "chpp/macros.h"
#include "chpp/platform/log.h"

namespace chpp {

namespace {

void onUartRxInterrupt(void *context) {
  UartLinkManager *manager = static_cast<UartLinkManager *>(context);
  manager->getUart()->DisableRxInterrupt();
  chppWorkThreadSignalFromLink(&manager->getTransportContext()->linkParams,
                               CHPP_TRANSPORT_SIGNAL_LINK_RX_PROCESS);
}

}  // anonymous namespace

UartLinkManager::UartLinkManager(struct ChppTransportState *context, UART *uart,
                                 uint8_t wakeOutPinNumber)
    : mTransportContext(context), mUart(uart), mWakeOutGpio(wakeOutPinNumber) {
  mWakeOutGpio.SetDirection(GPIO::DIRECTION::OUTPUT);
  mWakeOutGpio.Clear();
}

void UartLinkManager::init() {
  mUart->RegisterRxCallback(onUartRxInterrupt, this);
  mUart->EnableRxInterrupt();
}

bool UartLinkManager::prepareTxPacket(uint8_t *buf, size_t len) {
  bool success = !hasTxPacket();
  if (!success) {
    CHPP_LOGE("Cannot prepare packet while one pending");
  } else {
    mCurrentBuffer = buf;
    mCurrentBufferLen = len;
  }
  return success;
}

bool UartLinkManager::startTransaction() {
  bool success = true;
  mWakeOutGpio.Set(true /* set */);

  // TODO: Wait for wake_in GPIO high

  if (hasTxPacket()) {
    int bytesTransmitted = mUart->Tx(mCurrentBuffer, mCurrentBufferLen);

    // Deassert wake_out as soon as data is transmitted, per specifications.
    mWakeOutGpio.Clear();

    if (static_cast<size_t>(bytesTransmitted) != mCurrentBufferLen) {
      CHPP_LOGE("Failed to transmit data");
      success = false;
    }

    clearTxPacket();
  } else {
    // TODO: Wait for pulse width requirement per specifications.
    mWakeOutGpio.Clear();
  }

  // TODO: Wait for wake_in GPIO low
  return success;
}

void UartLinkManager::processRxSamples() {
  int ch;
  while ((ch = mUart->GetChar()) != EOF && mRxBufIndex < kRxBufSize) {
    mRxBuf[mRxBufIndex++] = static_cast<uint8_t>(ch);
  }

  chppRxDataCb(mTransportContext, mRxBuf, mRxBufIndex);
  mRxBufIndex = 0;
  mUart->EnableRxInterrupt();
}

bool UartLinkManager::hasTxPacket() const {
  return mCurrentBuffer != nullptr && mUart != nullptr;
}

void UartLinkManager::clearTxPacket() {
  mCurrentBuffer = nullptr;
}

}  // namespace chpp