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- // Copyright 2013 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "ui/gl/sync_control_vsync_provider.h"
- #include <math.h>
- #include "base/logging.h"
- #include "base/time/time.h"
- #include "base/trace_event/trace_event.h"
- #include "build/build_config.h"
- #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- // These constants define a reasonable range for a calculated refresh interval.
- // Calculating refreshes out of this range will be considered a fatal error.
- const int64_t kMinVsyncIntervalUs = base::Time::kMicrosecondsPerSecond / 400;
- const int64_t kMaxVsyncIntervalUs = base::Time::kMicrosecondsPerSecond / 10;
- // How much noise we'll tolerate between successive computed intervals before
- // we think the latest computed interval is invalid (noisey due to
- // monitor configuration change, moving a window between monitors, etc.).
- const double kRelativeIntervalDifferenceThreshold = 0.05;
- #endif
- namespace gl {
- SyncControlVSyncProvider::SyncControlVSyncProvider() : gfx::VSyncProvider() {
- #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- // On platforms where we can't get an accurate reading on the refresh
- // rate we fall back to the assumption that we're displaying 60 frames
- // per second.
- last_good_interval_ = base::Seconds(1) / 60;
- #endif
- }
- SyncControlVSyncProvider::~SyncControlVSyncProvider() {}
- void SyncControlVSyncProvider::GetVSyncParameters(
- UpdateVSyncCallback callback) {
- base::TimeTicks timebase;
- base::TimeDelta interval;
- if (GetVSyncParametersIfAvailable(&timebase, &interval))
- std::move(callback).Run(timebase, interval);
- }
- bool SyncControlVSyncProvider::GetVSyncParametersIfAvailable(
- base::TimeTicks* timebase_out,
- base::TimeDelta* interval_out) {
- TRACE_EVENT0("gpu", "SyncControlVSyncProvider::GetVSyncParameters");
- #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- // The actual clock used for the system time returned by glXGetSyncValuesOML
- // is unspecified. In practice, the clock used is likely to be either
- // CLOCK_REALTIME or CLOCK_MONOTONIC, so we compare the returned time to the
- // current time according to both clocks, and assume that the returned time
- // was produced by the clock whose current time is closest to it, subject
- // to the restriction that the returned time must not be in the future
- // (since it is the time of a vblank that has already occurred).
- int64_t system_time;
- int64_t media_stream_counter;
- int64_t swap_buffer_counter;
- if (!GetSyncValues(&system_time, &media_stream_counter, &swap_buffer_counter))
- return false;
- // Both Intel and Mali drivers will return TRUE for GetSyncValues
- // but a value of 0 for MSC if they cannot access the CRTC data structure
- // associated with the surface. crbug.com/231945
- invalid_msc_ = (media_stream_counter == 0);
- if (invalid_msc_)
- return false;
- struct timespec real_time;
- clock_gettime(CLOCK_REALTIME, &real_time);
- // Note: A thread context switch could happen here, between the sampling of
- // the two different clocks.
- const base::TimeTicks monotonic_time = base::TimeTicks::Now();
- DCHECK_EQ(base::TimeTicks::GetClock(),
- base::TimeTicks::Clock::LINUX_CLOCK_MONOTONIC);
- int64_t real_time_in_microseconds =
- base::TimeDelta::FromTimeSpec(real_time).InMicroseconds();
- int64_t monotonic_time_in_microseconds =
- monotonic_time.since_origin().InMicroseconds();
- // We need the time according to CLOCK_MONOTONIC, so if we've been given
- // a time from CLOCK_REALTIME, we need to convert.
- bool time_conversion_needed =
- llabs(system_time - real_time_in_microseconds) <
- llabs(system_time - monotonic_time_in_microseconds);
- if (time_conversion_needed)
- system_time += monotonic_time_in_microseconds - real_time_in_microseconds;
- // Return if |system_time| is more than 1 frames in the future.
- int64_t interval_in_microseconds = last_good_interval_.InMicroseconds();
- if (system_time > monotonic_time_in_microseconds + interval_in_microseconds)
- return false;
- // If |system_time| is slightly in the future, adjust it to the previous
- // frame and use the last frame counter to prevent issues in the callback.
- if (system_time > monotonic_time_in_microseconds) {
- system_time -= interval_in_microseconds;
- media_stream_counter--;
- }
- if (monotonic_time_in_microseconds - system_time >
- base::Time::kMicrosecondsPerSecond)
- return false;
- const base::TimeTicks timebase =
- base::TimeTicks() + base::Microseconds(system_time);
- // Only need the previous calculated interval for our filtering.
- while (last_computed_intervals_.size() > 1)
- last_computed_intervals_.pop();
- int32_t numerator, denominator;
- if (GetMscRate(&numerator, &denominator) && numerator) {
- last_computed_intervals_.push(base::Seconds(denominator) / numerator);
- } else if (!last_timebase_.is_null()) {
- base::TimeDelta timebase_diff = timebase - last_timebase_;
- int64_t counter_diff = media_stream_counter - last_media_stream_counter_;
- if (counter_diff > 0 && timebase > last_timebase_)
- last_computed_intervals_.push(timebase_diff / counter_diff);
- }
- if (last_computed_intervals_.size() == 2) {
- const base::TimeDelta& old_interval = last_computed_intervals_.front();
- const base::TimeDelta& new_interval = last_computed_intervals_.back();
- double relative_change =
- fabs(old_interval.InMillisecondsF() - new_interval.InMillisecondsF()) /
- new_interval.InMillisecondsF();
- if (relative_change < kRelativeIntervalDifferenceThreshold) {
- if (new_interval.InMicroseconds() < kMinVsyncIntervalUs ||
- new_interval.InMicroseconds() > kMaxVsyncIntervalUs) {
- // For ChromeOS, we get the refresh interval from DRM through Ozone.
- // For Linux, we could use XRandR.
- // http://crbug.com/340851
- LOG(ERROR)
- << "Calculated bogus refresh interval=" << new_interval
- << ", last_timebase_=" << last_timebase_
- << ", timebase=" << timebase
- << ", last_media_stream_counter_=" << last_media_stream_counter_
- << ", media_stream_counter=" << media_stream_counter;
- } else {
- last_good_interval_ = new_interval;
- }
- }
- }
- last_timebase_ = timebase;
- last_media_stream_counter_ = media_stream_counter;
- *timebase_out = timebase;
- *interval_out = last_good_interval_;
- return true;
- #else
- return false;
- #endif // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- }
- bool SyncControlVSyncProvider::SupportGetVSyncParametersIfAvailable() const {
- #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
- return true;
- #else
- return false;
- #endif
- }
- } // namespace gl
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