drm/VSyncWorker.cpp

/*
 * Copyright (C) 2015 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.
 */

#define LOG_TAG "hwc-vsync-worker"

#include "VSyncWorker.h"

#include <xf86drm.h>
#include <xf86drmMode.h>

#include <cstdlib>
#include <cstring>
#include <ctime>

#include "utils/log.h"

namespace android {

VSyncWorker::VSyncWorker() : Worker("vsync", HAL_PRIORITY_URGENT_DISPLAY){};

auto VSyncWorker::Init(DrmDisplayPipeline *pipe,
                       std::function<void(uint64_t /*timestamp*/)> callback)
    -> int {
  pipe_ = pipe;
  callback_ = std::move(callback);

  return InitWorker();
}

void VSyncWorker::VSyncControl(bool enabled) {
  Lock();
  enabled_ = enabled;
  last_timestamp_ = -1;
  Unlock();

  Signal();
}

/*
 * Returns the timestamp of the next vsync in phase with last_timestamp_.
 * For example:
 *  last_timestamp_ = 137
 *  frame_ns = 50
 *  current = 683
 *
 *  ret = (50 * ((683 - 137)/50 + 1)) + 137
 *  ret = 687
 *
 *  Thus, we must sleep until timestamp 687 to maintain phase with the last
 *  timestamp.
 */
int64_t VSyncWorker::GetPhasedVSync(int64_t frame_ns, int64_t current) const {
  if (last_timestamp_ < 0)
    return current + frame_ns;

  return frame_ns * ((current - last_timestamp_) / frame_ns + 1) +
         last_timestamp_;
}

static const int64_t kOneSecondNs = 1LL * 1000 * 1000 * 1000;

int VSyncWorker::SyntheticWaitVBlank(int64_t *timestamp) {
  struct timespec vsync {};
  int ret = clock_gettime(CLOCK_MONOTONIC, &vsync);
  if (ret)
    return ret;

  float refresh = 60.0F;  // Default to 60Hz refresh rate
  if (pipe_ != nullptr &&
      pipe_->connector->Get()->GetActiveMode().GetVRefresh() != 0.0F) {
    refresh = pipe_->connector->Get()->GetActiveMode().GetVRefresh();
  }

  auto phased_timestamp = GetPhasedVSync(kOneSecondNs /
                                             static_cast<int>(refresh),
                                         vsync.tv_sec * kOneSecondNs +
                                             vsync.tv_nsec);
  vsync.tv_sec = phased_timestamp / kOneSecondNs;
  vsync.tv_nsec = int(phased_timestamp - (vsync.tv_sec * kOneSecondNs));
  do {
    ret = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &vsync, nullptr);
  } while (ret == EINTR);
  if (ret)
    return ret;

  *timestamp = (int64_t)vsync.tv_sec * kOneSecondNs + (int64_t)vsync.tv_nsec;
  return 0;
}

void VSyncWorker::Routine() {
  int ret = 0;

  Lock();
  if (!enabled_) {
    ret = WaitForSignalOrExitLocked();
    if (ret == -EINTR) {
      Unlock();
      return;
    }
  }

  auto *pipe = pipe_;
  Unlock();

  ret = -EAGAIN;
  int64_t timestamp = 0;
  drmVBlank vblank{};

  if (pipe != nullptr) {
    auto high_crtc = (pipe->crtc->Get()->GetIndexInResArray()
                      << DRM_VBLANK_HIGH_CRTC_SHIFT);

    vblank.request.type = (drmVBlankSeqType)(DRM_VBLANK_RELATIVE |
                                             (high_crtc &
                                              DRM_VBLANK_HIGH_CRTC_MASK));
    vblank.request.sequence = 1;

    ret = drmWaitVBlank(pipe->device->GetFd(), &vblank);
    if (ret == -EINTR)
      return;
  }

  if (ret) {
    ret = SyntheticWaitVBlank(&timestamp);
    if (ret)
      return;
  } else {
    timestamp = (int64_t)vblank.reply.tval_sec * kOneSecondNs +
                (int64_t)vblank.reply.tval_usec * 1000;
  }

  if (!enabled_)
    return;

  if (callback_) {
    callback_(timestamp);
  }

  last_timestamp_ = timestamp;
}
}  // namespace android