Floss: use CLOCK_MONOTONIC_RAW in A2DP encoding for TARGET_FLOSS

Floss uses CLOCK_MONOTONIC and CLOCK_BOOTTIME for various timestamp and
timediff calculation.

This causes glitches when the audio stack calculates timestamp and
schedules with CLOCK_MONOTONIC_RAW.

In this CL, we swap out the clock used in scheduling A2DP packet
encoding to use CLOCK_MONOTONIC_RAW when the build is targeted to Floss.

Note that we intentionally leave the timestamps in metrics/stats
untouched since they have different purposes (e.g., allowing to match
with other timestamps across applications).

Bug: 241816575
Tag: #floss
Test: Build and verify A2DP doesn't glitch

Change-Id: I275208e33285282911c49caa599cbb14a810bfa9

5 files changed, 67 insertions, 5 deletions

diff --git a/system/btif/src/btif_a2dp_source.cc b/system/btif/src/btif_a2dp_source.cc
index f13abac71a..55f46dd31c 100644
--- a/system/btif/src/btif_a2dp_source.cc
+++ b/system/btif/src/btif_a2dp_source.cc
@@ -895,8 +895,15 @@ 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();
-  log_tstamps_us("A2DP Source tx timer", timestamp_us);
+  uint64_t stats_timestamp_us = timestamp_us;
+#else
+  uint64_t timestamp_us = bluetooth::common::time_get_os_monotonic_raw_us();
+  uint64_t stats_timestamp_us = bluetooth::common::time_get_os_boottime_us();
+#endif
+
+  log_tstamps_us("A2DP Source tx scheduling timer", timestamp_us);
 
   if (!btif_a2dp_source_cb.media_alarm.IsScheduled()) {
     LOG_ERROR("%s: ERROR Media task Scheduled after Suspend", __func__);
@@ -916,7 +923,7 @@ static void btif_a2dp_source_audio_handle_timer(void) {
   btif_a2dp_source_cb.encoder_interface->send_frames(timestamp_us);
   bta_av_ci_src_data_ready(BTA_AV_CHNL_AUDIO);
   update_scheduling_stats(&btif_a2dp_source_cb.stats.tx_queue_enqueue_stats,
-                          timestamp_us,
+                          stats_timestamp_us,
                           btif_a2dp_source_cb.encoder_interval_ms * 1000);
 }
 
diff --git a/system/common/time_util.cc b/system/common/time_util.cc
index 273be181d0..d77c17c0c8 100644
--- a/system/common/time_util.cc
+++ b/system/common/time_util.cc
@@ -42,6 +42,13 @@ uint64_t time_gettimeofday_us() {
          static_cast<uint64_t>(tv.tv_usec);
 }
 
+uint64_t time_get_os_monotonic_raw_us() {
+  struct timespec ts_now = {};
+  clock_gettime(CLOCK_MONOTONIC_RAW, &ts_now);
+
+  return ((uint64_t)ts_now.tv_sec * 1000000L) +
+         ((uint64_t)ts_now.tv_nsec / 1000);
+}
 }  // namespace common
 
-}  // namespace bluetooth
\ No newline at end of file
+}  // namespace bluetooth
diff --git a/system/common/time_util.h b/system/common/time_util.h
index 70a64d2cba..16808135c3 100644
--- a/system/common/time_util.h
+++ b/system/common/time_util.h
@@ -33,6 +33,8 @@ uint64_t time_get_os_boottime_us();
 // Get the current wall clock time in microseconds.
 uint64_t time_gettimeofday_us();
 
+// Get the OS monotonic raw time in microseconds.
+uint64_t time_get_os_monotonic_raw_us();
 }  // namespace common
 
 }  // namespace bluetooth
diff --git a/system/common/time_util_unittest.cc b/system/common/time_util_unittest.cc
index 77e205d3a6..eb21aee5ad 100644
--- a/system/common/time_util_unittest.cc
+++ b/system/common/time_util_unittest.cc
@@ -42,8 +42,17 @@ TEST(TimeTest, test_time_get_os_boottime_us_not_zero) {
 }
 
 //
+// Test that the return value of
+// bluetooth::common::time_get_os_monotonic_raw_us() is not zero.
+//
+TEST(TimeTest, test_time_get_os_monotonic_raw_us_not_zero) {
+  uint64_t t1 = bluetooth::common::time_get_os_monotonic_raw_us();
+  ASSERT_GT(t1, uint64_t(0));
+}
+
+//
 // Test that the return value of bluetooth::common::time_get_os_boottime_ms()
-// is monotonically increasing within reasonable boundries.
+// is monotonically increasing within reasonable boundaries.
 //
 TEST(TimeTest, test_time_get_os_boottime_ms_increases_upper_bound) {
   uint64_t t1 = bluetooth::common::time_get_os_boottime_ms();
@@ -53,7 +62,7 @@ TEST(TimeTest, test_time_get_os_boottime_ms_increases_upper_bound) {
 
 //
 // Test that the return value of bluetooth::common::time_get_os_boottime_us()
-// is monotonically increasing within reasonable boundries.
+// is monotonically increasing within reasonable boundaries.
 //
 TEST(TimeTest, test_time_get_os_boottime_us_increases_upper_bound) {
   uint64_t t1 = bluetooth::common::time_get_os_boottime_us();
@@ -62,6 +71,17 @@ TEST(TimeTest, test_time_get_os_boottime_us_increases_upper_bound) {
 }
 
 //
+// Test that the return value of
+// bluetooth::common::time_get_os_monotonic_raw_us() is monotonically increasing
+// within reasonable boundaries.
+//
+TEST(TimeTest, test_time_get_os_monotonic_raw_time_us_increases_upper_bound) {
+  uint64_t t1 = bluetooth::common::time_get_os_monotonic_raw_us();
+  uint64_t t2 = bluetooth::common::time_get_os_monotonic_raw_us();
+  ASSERT_TRUE((t2 - t1) < TEST_TIME_DELTA_UPPER_BOUND_MS * 1000);
+}
+
+//
 // Test that the return value of bluetooth::common::time_get_os_boottime_ms()
 // is increasing.
 //
@@ -105,6 +125,28 @@ TEST(TimeTest, test_time_get_os_boottime_us_increases_lower_bound) {
 }
 
 //
+// Test that the return value of
+// bluetooth::common::time_get_os_monotonic_raw_us() is increasing.
+//
+TEST(TimeTest, test_time_get_os_monotonic_raw_us_increases_lower_bound) {
+  static const uint64_t TEST_TIME_SLEEP_US = 100 * 1000;
+  struct timespec delay = {};
+
+  delay.tv_sec = TEST_TIME_SLEEP_US / (1000 * 1000);
+  delay.tv_nsec = 1000 * (TEST_TIME_SLEEP_US % (1000 * 1000));
+
+  // Take two timestamps with sleep in-between
+  uint64_t t1 = bluetooth::common::time_get_os_monotonic_raw_us();
+  int err = nanosleep(&delay, &delay);
+  uint64_t t2 = bluetooth::common::time_get_os_monotonic_raw_us();
+
+  ASSERT_EQ(err, 0);
+  ASSERT_GT(t2, t1);
+  ASSERT_TRUE((t2 - t1) >= TEST_TIME_SLEEP_US);
+  ASSERT_TRUE((t2 - t1) < TEST_TIME_DELTA_UPPER_BOUND_MS * 1000);
+}
+
+//
 // Test that the return value of bluetooth::common::time_gettimeofday_us() is
 // not zero.
 //
diff --git a/system/test/mock/mock_common_time_util.cc b/system/test/mock/mock_common_time_util.cc
index e29368e8bb..7a9c4d6a13 100644
--- a/system/test/mock/mock_common_time_util.cc
+++ b/system/test/mock/mock_common_time_util.cc
@@ -47,6 +47,10 @@ uint64_t time_gettimeofday_us() {
   mock_function_count_map[__func__]++;
   return 0;
 }
+uint64_t time_get_os_monotonic_raw_us() {
+  mock_function_count_map[__func__]++;
+  return 0;
+}
 
 }  // namespace common
 }  // namespace bluetooth