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

8 files changed, 40 insertions, 19 deletions

diff --git a/system/bta/le_audio/audio_hal_client/audio_source_hal_client.cc b/system/bta/le_audio/audio_hal_client/audio_source_hal_client.cc
index 2a0768c5c9..6470edb6dd 100644
--- a/system/bta/le_audio/audio_hal_client/audio_source_hal_client.cc
+++ b/system/bta/le_audio/audio_hal_client/audio_source_hal_client.cc
@@ -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();
   }
diff --git a/system/btif/src/btif_a2dp_source.cc b/system/btif/src/btif_a2dp_source.cc
index a68af1d75e..ae955655f2 100644
--- a/system/btif/src/btif_a2dp_source.cc
+++ b/system/btif/src/btif_a2dp_source.cc
@@ -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);
 
diff --git a/system/common/repeating_timer.cc b/system/common/repeating_timer.cc
index 841343989f..f0a75ea69a 100644
--- a/system/common/repeating_timer.cc
+++ b/system/common/repeating_timer.cc
@@ -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()) {
diff --git a/system/common/repeating_timer.h b/system/common/repeating_timer.h
index 6398af224b..7f004c31fc 100644
--- a/system/common/repeating_timer.h
+++ b/system/common/repeating_timer.h
@@ -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);
diff --git a/system/common/time_util.cc b/system/common/time_util.cc
index d77c17c0c8..6799270ddf 100644
--- a/system/common/time_util.cc
+++ b/system/common/time_util.cc
@@ -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() {
diff --git a/system/common/time_util.h b/system/common/time_util.h
index 16808135c3..200c2bbd95 100644
--- a/system/common/time_util.h
+++ b/system/common/time_util.h
@@ -24,6 +24,10 @@ namespace bluetooth {
 
 namespace common {
 
+// Get the time aligned to the clock domain of the audio server, in
+// microseconds.
+uint64_t time_get_audio_server_tick_us();
+
 // Get the OS boot time in milliseconds.
 uint64_t time_get_os_boottime_ms();
 
diff --git a/system/gd/Android.bp b/system/gd/Android.bp
index 7fa3a5c1fe..6dee9b3f10 100644
--- a/system/gd/Android.bp
+++ b/system/gd/Android.bp
@@ -175,6 +175,7 @@ cc_defaults {
         "libbluetooth_crypto_toolbox",
         "libbluetooth_log",
         "libbluetooth_rust_interop",
+        "libbt-common",
         "libbt-platform-protos-lite",
         "libbt_shim_bridge",
         "libbt_shim_ffi",
@@ -241,6 +242,7 @@ cc_library {
     ],
     static_libs: [
         "libbluetooth-types",
+        "libbt-common",
         "libchrome",
         "libosi",
     ],
@@ -262,6 +264,7 @@ cc_library {
     ],
     static_libs: [
         "libbluetooth-types",
+        "libbt-common",
         "libchrome",
         "libosi",
     ],
@@ -316,6 +319,7 @@ cc_binary {
         "libbluetooth_ras_pdl",
         "libbluetooth_rust_interop",
         "libbluetooth_smp_pdl",
+        "libbt-common",
         "libbt_shim_bridge",
         "libbt_shim_ffi",
         "libchrome",
@@ -484,6 +488,7 @@ cc_test {
         "libbluetooth_ras_pdl",
         "libbluetooth_rust_interop",
         "libbluetooth_smp_pdl",
+        "libbt-common",
         "libbt-platform-protos-lite",
         "libbt_shim_bridge",
         "libbt_shim_ffi",
@@ -632,6 +637,7 @@ cc_defaults {
         "libbluetooth_gd_fuzzing",
         "libbluetooth_log",
         "libbluetooth_rust_interop",
+        "libbt-common",
         "libbt_shim_bridge",
         "libbt_shim_ffi",
         "libchrome",
diff --git a/system/gd/hal/link_clocker.cc b/system/gd/hal/link_clocker.cc
index 830c90a4ab..a077f126f2 100644
--- a/system/gd/hal/link_clocker.cc
+++ b/system/gd/hal/link_clocker.cc
@@ -20,6 +20,8 @@
 
 #include <algorithm>
 
+#include "common/time_util.h"
+
 namespace bluetooth::hal {
 
 static class : public ReadClockHandler {
@@ -87,8 +89,7 @@ void LinkClocker::OnHciEvent(const HciPacket& packet) {
   // getting the local timestamp from the bound gd HCI event callback
   // adds jitter.
 
-  auto timestamp = std::chrono::system_clock::now().time_since_epoch();
-  unsigned timestamp_us = std::chrono::duration_cast<std::chrono::microseconds>(timestamp).count();
+  unsigned timestamp_us = bluetooth::common::time_get_audio_server_tick_us();
 
   (*g_read_clock_handler).OnEvent(timestamp_us, bt_clock << 4);
 }