a2dp media packet sent too slow, which cause packet overflow.
the error message: btif_media_aa_prep_2_send congestion buf count 24
The reason is we increase all bluedroid thread related TX data path priority:
media, timer, BTU and HCI_WORKER, but we didn't increase the RX data path
priority: userial_read_thread. If the RX thread is blocked, it will also
affect TX, because the HCI have flow control, we need receive HCI Number of
Completed Packets Events to continue send packet to the controller.
If we HCI complete Packets Event packets is blocked, the HCI flow control
will block the HCI packet trnasmission until we get HCI complete packets
event to know how many buffer is available in the controller.
I tested with a chrysler CIP/VP4 carkit which show this error message,
After I apply this fix, I can't reproduce this problem any more.
This look like good fix for this issue.
bug:8252054
Change-Id: Ic78b9abb69648c50aa63e2b3c8b90038018fb6b5
diff --git a/hci/src/userial.c b/hci/src/userial.c
index d87bea1..8e5bf6c 100644
--- a/hci/src/userial.c
+++ b/hci/src/userial.c
@@ -37,6 +37,7 @@
#include "utils.h"
#include "bt_vendor_lib.h"
#include <sys/prctl.h>
+#include "bt_utils.h"
/******************************************************************************
** Constants & Macros
@@ -247,6 +248,8 @@
rx_flow_on = TRUE;
userial_running = 1;
+ raise_priority_a2dp(TASK_HIGH_USERIAL_READ);
+
while (userial_running)
{
if (bt_hc_cbacks)
diff --git a/hci/src/userial_mct.c b/hci/src/userial_mct.c
index 5c33285..3c59384 100644
--- a/hci/src/userial_mct.c
+++ b/hci/src/userial_mct.c
@@ -36,6 +36,7 @@
#include "userial.h"
#include "utils.h"
#include "bt_vendor_lib.h"
+#include "bt_utils.h"
/******************************************************************************
** Constants & Macros
@@ -148,6 +149,8 @@
rx_flow_on = TRUE;
userial_running = 1;
+ raise_priority_a2dp(TASK_HIGH_USERIAL_READ);
+
while (userial_running)
{
/* Initialize the input fd set */
diff --git a/utils/include/bt_utils.h b/utils/include/bt_utils.h
index ef4fc18..ac18f07 100644
--- a/utils/include/bt_utils.h
+++ b/utils/include/bt_utils.h
@@ -28,6 +28,7 @@
TASK_HIGH_GKI_TIMER,
TASK_HIGH_BTU,
TASK_HIGH_HCI_WORKER,
+ TASK_HIGH_USERIAL_READ,
TASK_HIGH_MAX
} tHIGH_PRIORITY_TASK;