diff --git a/services/camera/libcameraservice/device3/Camera3Device.cpp b/services/camera/libcameraservice/device3/Camera3Device.cpp
index 25c9d3c..c85d00f 100644
--- a/services/camera/libcameraservice/device3/Camera3Device.cpp
+++ b/services/camera/libcameraservice/device3/Camera3Device.cpp
@@ -2261,8 +2261,8 @@
                 return NULL;
             }
         }
-        // Check if stream is being prepared
-        if (mInputStream->isPreparing()) {
+        // Check if stream prepare is blocking requests.
+        if (mInputStream->isBlockedByPrepare()) {
             CLOGE("Request references an input stream that's being prepared!");
             return NULL;
         }
@@ -2312,8 +2312,8 @@
                 return NULL;
             }
         }
-        // Check if stream is being prepared
-        if (stream->isPreparing()) {
+        // Check if stream prepare is blocking requests.
+        if (stream->isBlockedByPrepare()) {
             CLOGE("Request references an output stream that's being prepared!");
             return NULL;
         }
@@ -4871,7 +4871,8 @@
                 // Only try to prepare video stream on the first video request.
                 mPrepareVideoStream = false;
 
-                res = outputStream->startPrepare(Camera3StreamInterface::ALLOCATE_PIPELINE_MAX);
+                res = outputStream->startPrepare(Camera3StreamInterface::ALLOCATE_PIPELINE_MAX,
+                        false /*blockRequest*/);
                 while (res == NOT_ENOUGH_DATA) {
                     res = outputStream->prepareNextBuffer();
                 }
@@ -5536,7 +5537,7 @@
     Mutex::Autolock l(mLock);
     sp<NotificationListener> listener = mListener.promote();
 
-    res = stream->startPrepare(maxCount);
+    res = stream->startPrepare(maxCount, true /*blockRequest*/);
     if (res == OK) {
         // No preparation needed, fire listener right off
         ALOGV("%s: Stream %d already prepared", __FUNCTION__, stream->getId());
@@ -5624,7 +5625,7 @@
 
     auto it = mPendingStreams.begin();
     for (; it != mPendingStreams.end();) {
-        res = it->second->startPrepare(it->first);
+        res = it->second->startPrepare(it->first, true /*blockRequest*/);
         if (res == OK) {
             if (listener != NULL) {
                 listener->notifyPrepared(it->second->getId());
diff --git a/services/camera/libcameraservice/device3/Camera3Stream.cpp b/services/camera/libcameraservice/device3/Camera3Stream.cpp
index 8747661..6870350 100644
--- a/services/camera/libcameraservice/device3/Camera3Stream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3Stream.cpp
@@ -61,6 +61,7 @@
     mOldUsage(0),
     mOldMaxBuffers(0),
     mPrepared(false),
+    mPrepareBlockRequest(true),
     mPreparedBufferIdx(0),
     mLastMaxCount(Camera3StreamInterface::ALLOCATE_PIPELINE_MAX),
     mBufferLimitLatency(kBufferLimitLatencyBinSize),
@@ -327,6 +328,7 @@
     // Reset prepared state, since buffer config has changed, and existing
     // allocations are no longer valid
     mPrepared = false;
+    mPrepareBlockRequest = true;
     mStreamUnpreparable = false;
 
     status_t res;
@@ -381,7 +383,7 @@
     return mStreamUnpreparable;
 }
 
-status_t Camera3Stream::startPrepare(int maxCount) {
+status_t Camera3Stream::startPrepare(int maxCount, bool blockRequest) {
     ATRACE_CALL();
 
     Mutex::Autolock l(mLock);
@@ -413,8 +415,6 @@
         return INVALID_OPERATION;
     }
 
-
-
     size_t pipelineMax = getBufferCountLocked();
     size_t clampedCount = (pipelineMax < static_cast<size_t>(maxCount)) ?
             pipelineMax : static_cast<size_t>(maxCount);
@@ -422,6 +422,7 @@
             pipelineMax : clampedCount;
 
     mPrepared = bufferCount <= mLastMaxCount;
+    mPrepareBlockRequest = blockRequest;
 
     if (mPrepared) return OK;
 
@@ -435,9 +436,9 @@
     return NOT_ENOUGH_DATA;
 }
 
-bool Camera3Stream::isPreparing() const {
+bool Camera3Stream::isBlockedByPrepare() const {
     Mutex::Autolock l(mLock);
-    return mState == STATE_PREPARING;
+    return mState == STATE_PREPARING && mPrepareBlockRequest;
 }
 
 bool Camera3Stream::isAbandoned() const {
diff --git a/services/camera/libcameraservice/device3/Camera3Stream.h b/services/camera/libcameraservice/device3/Camera3Stream.h
index e6fb7f9..9c0f4c0 100644
--- a/services/camera/libcameraservice/device3/Camera3Stream.h
+++ b/services/camera/libcameraservice/device3/Camera3Stream.h
@@ -232,6 +232,11 @@
      *
      * This call performs no allocation, so is quick to call.
      *
+     * blockRequest specifies whether prepare will block upcoming capture
+     * request. This flag should only be set to false if the caller guarantees
+     * the whole buffer preparation process is done before capture request
+     * comes in.
+     *
      * Returns:
      *    OK if no more buffers need to be preallocated
      *    NOT_ENOUGH_DATA if calls to prepareNextBuffer are needed to finish
@@ -240,12 +245,12 @@
      *    INVALID_OPERATION if called when not in CONFIGURED state, or a
      *        valid buffer has already been returned to this stream.
      */
-    status_t         startPrepare(int maxCount);
+    status_t         startPrepare(int maxCount, bool blockRequest);
 
     /**
-     * Check if the stream is mid-preparing.
+     * Check if the request on a stream is blocked by prepare.
      */
-    bool             isPreparing() const;
+    bool             isBlockedByPrepare() const;
 
     /**
      * Continue stream buffer preparation by allocating the next
@@ -534,6 +539,7 @@
     // has been called sufficient number of times, or stream configuration
     // had to register buffers with the HAL
     bool mPrepared;
+    bool mPrepareBlockRequest;
 
     Vector<camera3_stream_buffer_t> mPreparedBuffers;
     size_t mPreparedBufferIdx;
diff --git a/services/camera/libcameraservice/device3/Camera3StreamInterface.h b/services/camera/libcameraservice/device3/Camera3StreamInterface.h
index 2dde1c3..3d45c89 100644
--- a/services/camera/libcameraservice/device3/Camera3StreamInterface.h
+++ b/services/camera/libcameraservice/device3/Camera3StreamInterface.h
@@ -160,6 +160,11 @@
      * PREPARING state. Otherwise, returns NOT_ENOUGH_DATA and transitions
      * to PREPARING.
      *
+     * blockRequest specifies whether prepare will block upcoming capture
+     * request. This flag should only be set to false if the caller guarantees
+     * the whole buffer preparation process is done before capture request
+     * comes in.
+     *
      * Returns:
      *    OK if no more buffers need to be preallocated
      *    NOT_ENOUGH_DATA if calls to prepareNextBuffer are needed to finish
@@ -168,12 +173,12 @@
      *    INVALID_OPERATION if called when not in CONFIGURED state, or a
      *        valid buffer has already been returned to this stream.
      */
-    virtual status_t startPrepare(int maxCount) = 0;
+    virtual status_t startPrepare(int maxCount, bool blockRequest) = 0;
 
     /**
-     * Check if the stream is mid-preparing.
+     * Check if the request on a stream is blocked by prepare.
      */
-    virtual bool     isPreparing() const = 0;
+    virtual bool     isBlockedByPrepare() const = 0;
 
     /**
      * Continue stream buffer preparation by allocating the next