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Commit 1e43219c authored by Jeremy Wu's avatar Jeremy Wu
Browse files

Floss: address clock drift in asrc 

Since ISO packets are sent out at fixed intervals, the |RepeatingTimer|
utility determines an important time domain.

By default, it uses NTP-adjusted clocks, the difference between the
timestamps of which is compatible with
|CLOCK_REALTIME/MONOTONIC/BOOTTIME| and such, aligning with Android's
audio server.

However, CrAS uses |CLOCK_MONOTONIC_RAW|, which is another time domain,
unaffected by NTP, and this can cause xruns when the clock drift
accumulates, which does relatively quickly.

This CL adds a parameter to |RepeatingTimer| to allow scheduling based
on |CLOCK_MONOTONIC_RAW|, where despite each |DelayedCallback| can still
drift (since libchrome schedulers use NTP-adjusted clocks), in the long
run they are aligned.

Bug: 333334341
Test: m Bluetooth
Flag: EXEMPT floss only changes

Change-Id: Ie90952138d53a67171f526db55edd604306a96f6
parent ba2e6728

system/bta/le_audio/audio_hal_client/audio_source_hal_client.cc

+4 −1
Original line number Diff line number Diff line
@@ -74,7 +74,10 @@ class SourceImpl : public LeAudioSourceAudioHalClient { 
  // Internal functionality

  SourceImpl(bool is_broadcaster)

      : le_audio_sink_hal_state_(HAL_UNINITIALIZED),

        is_broadcaster_(is_broadcaster){};

        audio_timer_(

            /* clock_tick_us= */ bluetooth::common::

                time_get_audio_server_tick_us),

        is_broadcaster_(is_broadcaster) {}

  ~SourceImpl() override {

    if (le_audio_sink_hal_state_ != HAL_UNINITIALIZED) Release();

  }

system/btif/src/btif_a2dp_source.cc

+1 −6
Original line number Diff line number Diff line
@@ -898,13 +898,8 @@ static void btif_a2dp_source_audio_tx_stop_event(void) { 
static void btif_a2dp_source_audio_handle_timer(void) {

  if (btif_av_is_a2dp_offload_running()) return;



#ifndef TARGET_FLOSS

  uint64_t timestamp_us = bluetooth::common::time_get_os_boottime_us();

  uint64_t stats_timestamp_us = timestamp_us;

#else

  uint64_t timestamp_us = bluetooth::common::time_get_os_monotonic_raw_us();

  uint64_t timestamp_us = bluetooth::common::time_get_audio_server_tick_us();

  uint64_t stats_timestamp_us = bluetooth::common::time_get_os_boottime_us();

#endif



  log_tstamps_us("A2DP Source tx scheduling timer", timestamp_us);

system/common/repeating_timer.cc

+5 −6
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ 
#include <bluetooth/log.h>



#include "message_loop_thread.h"

#include "time_util.h"



namespace bluetooth {
@@ -47,7 +46,7 @@ bool RepeatingTimer::SchedulePeriodic( 
    return false;

  }



  uint64_t time_now_us = time_get_os_boottime_us();

  uint64_t time_now_us = clock_tick_us_();

  uint64_t time_next_task_us = time_now_us + period.count();

  std::lock_guard<std::recursive_mutex> api_lock(api_mutex_);

  if (thread == nullptr) {
@@ -61,7 +60,7 @@ bool RepeatingTimer::SchedulePeriodic( 
      base::Bind(&RepeatingTimer::RunTask, base::Unretained(this)));

  message_loop_thread_ = thread;

  period_ = period;

  uint64_t time_until_next_us = time_next_task_us - time_get_os_boottime_us();

  uint64_t time_until_next_us = time_next_task_us - clock_tick_us_();

  if (!thread->DoInThreadDelayed(

          from_here, task_wrapper_.callback(),

          std::chrono::microseconds(time_until_next_us))) {
@@ -139,7 +138,7 @@ void RepeatingTimer::RunTask() { 


  int64_t period_us = period_.count();

  expected_time_next_task_us_ += period_us;

  uint64_t time_now_us = time_get_os_boottime_us();

  uint64_t time_now_us = clock_tick_us_();

  int64_t remaining_time_us = expected_time_next_task_us_ - time_now_us;

  if (remaining_time_us < 0) {

    // if remaining_time_us is negative, schedule the task to the nearest
@@ -150,9 +149,9 @@ void RepeatingTimer::RunTask() { 
      FROM_HERE, task_wrapper_.callback(),

      std::chrono::microseconds(remaining_time_us));



  uint64_t time_before_task_us = time_get_os_boottime_us();

  uint64_t time_before_task_us = clock_tick_us_();

  task_.Run();

  uint64_t time_after_task_us = time_get_os_boottime_us();

  uint64_t time_after_task_us = clock_tick_us_();

  auto task_time_us =

      static_cast<int64_t>(time_after_task_us - time_before_task_us);

  if (task_time_us > period_.count()) {

system/common/repeating_timer.h

+7 −2
Original line number Diff line number Diff line
@@ -23,6 +23,8 @@ 
#include <chrono>

#include <future>



#include "time_util.h"



namespace bluetooth {



namespace common {
@@ -38,7 +40,9 @@ class MessageLoopThread; 
 */

class RepeatingTimer final {

 public:

  RepeatingTimer() : expected_time_next_task_us_(0) {}

  RepeatingTimer(uint64_t (*clock_tick_us)(void) =

                     bluetooth::common::time_get_os_boottime_us)

      : expected_time_next_task_us_(0), clock_tick_us_(clock_tick_us) {}

  RepeatingTimer(const RepeatingTimer&) = delete;

  RepeatingTimer& operator=(const RepeatingTimer&) = delete;
@@ -83,7 +87,8 @@ class RepeatingTimer final { 
  base::CancelableClosure task_wrapper_;

  base::RepeatingClosure task_;

  std::chrono::microseconds period_;

  uint64_t expected_time_next_task_us_;  // Using clock boot time in time_util.h

  uint64_t expected_time_next_task_us_;

  uint64_t (*clock_tick_us_)(void);

  mutable std::recursive_mutex api_mutex_;

  void CancelHelper(std::promise<void> promise);

  void CancelClosure(std::promise<void> promise);

system/common/time_util.cc

+10 −2
Original line number Diff line number Diff line
@@ -16,15 +16,23 @@ 
 *

 ******************************************************************************/



#include "common/time_util.h"



#include <sys/time.h>

#include <time.h>



#include "common/time_util.h"



namespace bluetooth {



namespace common {



uint64_t time_get_audio_server_tick_us() {

#ifndef TARGET_FLOSS

  return time_get_os_boottime_us();

#else

  return time_get_os_monotonic_raw_us();

#endif

}



uint64_t time_get_os_boottime_ms() { return time_get_os_boottime_us() / 1000; }



uint64_t time_get_os_boottime_us() {