3 files changed, 100 insertions, 0 deletions

diff --git a/hwc2_device/HwcDisplay.cpp b/hwc2_device/HwcDisplay.cpp
index 02df28c..76e2745 100644
--- a/hwc2_device/HwcDisplay.cpp
+++ b/hwc2_device/HwcDisplay.cpp
@@ -602,6 +602,7 @@ HWC2::Error HwcDisplay::SetClientTarget(buffer_handle_t target,
    * https://cs.android.com/android/platform/superproject/+/master:hardware/interfaces/graphics/composer/2.1/utils/hal/include/composer-hal/2.1/ComposerClient.h;l=350;drc=944b68180b008456ed2eb4d4d329e33b19bd5166
    */
   if (target == nullptr) {
+    client_layer_.SwChainClearCache();
     return HWC2::Error::None;
   }
 
diff --git a/hwc2_device/HwcLayer.cpp b/hwc2_device/HwcLayer.cpp
index f57ad9b..c278732 100644
--- a/hwc2_device/HwcLayer.cpp
+++ b/hwc2_device/HwcLayer.cpp
@@ -174,6 +174,11 @@ void HwcLayer::ImportFb() {
 
   layer_data_.fb = {};
 
+  auto unique_id = BufferInfoGetter::GetInstance()->GetUniqueId(buffer_handle_);
+  if (unique_id && SwChainGetBufferFromCache(*unique_id)) {
+    return;
+  }
+
   layer_data_.bi = BufferInfoGetter::GetInstance()->GetBoInfo(buffer_handle_);
   if (!layer_data_.bi) {
     ALOGW("Unable to get buffer information (0x%p)", buffer_handle_);
@@ -191,6 +196,10 @@ void HwcLayer::ImportFb() {
     fb_import_failed_ = true;
     return;
   }
+
+  if (unique_id) {
+    SwChainAddCurrentBuffer(*unique_id);
+  }
 }
 
 void HwcLayer::PopulateLayerData(bool test) {
@@ -211,4 +220,75 @@ void HwcLayer::PopulateLayerData(bool test) {
   }
 }
 
+/* SwapChain Cache */
+
+bool HwcLayer::SwChainGetBufferFromCache(BufferUniqueId unique_id) {
+  if (swchain_lookup_table_.count(unique_id) == 0) {
+    return false;
+  }
+
+  int seq = swchain_lookup_table_[unique_id];
+
+  if (swchain_cache_.count(seq) == 0) {
+    return false;
+  }
+
+  auto& el = swchain_cache_[seq];
+  if (!el.bi) {
+    return false;
+  }
+
+  layer_data_.bi = el.bi;
+  layer_data_.fb = el.fb;
+
+  return true;
+}
+
+void HwcLayer::SwChainReassemble(BufferUniqueId unique_id) {
+  if (swchain_lookup_table_.count(unique_id) != 0) {
+    if (swchain_lookup_table_[unique_id] ==
+        int(swchain_lookup_table_.size()) - 1) {
+      /* Skip same buffer */
+      return;
+    }
+    if (swchain_lookup_table_[unique_id] == 0) {
+      swchain_reassembled_ = true;
+      return;
+    }
+    /* Tracking error */
+    SwChainClearCache();
+    return;
+  }
+
+  swchain_lookup_table_[unique_id] = int(swchain_lookup_table_.size());
+}
+
+void HwcLayer::SwChainAddCurrentBuffer(BufferUniqueId unique_id) {
+  if (!swchain_reassembled_) {
+    SwChainReassemble(unique_id);
+  }
+
+  if (swchain_reassembled_) {
+    if (swchain_lookup_table_.count(unique_id) == 0) {
+      SwChainClearCache();
+      return;
+    }
+
+    int seq = swchain_lookup_table_[unique_id];
+
+    if (swchain_cache_.count(seq) == 0) {
+      swchain_cache_[seq] = {};
+    }
+
+    swchain_cache_[seq].bi = layer_data_.bi;
+    swchain_cache_[seq].fb = layer_data_.fb;
+  }
+}
+
+void HwcLayer::SwChainClearCache() {
+  swchain_cache_.clear();
+  swchain_lookup_table_.clear();
+  swchain_reassembled_ = false;
+}
+
 }  // namespace android
\ No newline at end of file
diff --git a/hwc2_device/HwcLayer.h b/hwc2_device/HwcLayer.h
index 92e9476..41b3dbb 100644
--- a/hwc2_device/HwcLayer.h
+++ b/hwc2_device/HwcLayer.h
@@ -19,6 +19,7 @@
 
 #include <hardware/hwcomposer2.h>
 
+#include "bufferinfo/BufferInfoGetter.h"
 #include "compositor/LayerData.h"
 
 namespace android {
@@ -118,6 +119,24 @@ class HwcLayer {
   void ImportFb();
   bool bi_get_failed_{};
   bool fb_import_failed_{};
+
+  /* SwapChain Cache */
+ public:
+  void SwChainClearCache();
+
+ private:
+  struct SwapChainElement {
+    std::optional<BufferInfo> bi;
+    std::shared_ptr<DrmFbIdHandle> fb;
+  };
+
+  bool SwChainGetBufferFromCache(BufferUniqueId unique_id);
+  void SwChainReassemble(BufferUniqueId unique_id);
+  void SwChainAddCurrentBuffer(BufferUniqueId unique_id);
+
+  std::map<int /*seq_no*/, SwapChainElement> swchain_cache_;
+  std::map<BufferUniqueId, int /*seq_no*/> swchain_lookup_table_;
+  bool swchain_reassembled_{};
 };
 
 }  // namespace android