commit b1c7632ec53d3ba4d65643936b61e83c4cd63376
author Naseer Ahmed <naseer@codeaurora.org> Wed Oct 17 00:32:50 2012 -0400
committer Naseer Ahmed <naseer@codeaurora.org> Mon Dec 03 15:32:29 2012 -0500
tree 42e91ed379f2066f4f3ac40d285da45899473816
parent 09549f6d757194761ea26dc0bd0717b851d8f067

hwc: cache layers on framebuffer

In the cases where all the layers that are marked as HWC_FRAMEBUFFER did not
change, we can mark them as HWC_OVERLAY since their contents are already on the
framebuffer and do not need any additional processing.

This optimization shows power improvement for video playback.

Bug: 7623741
Change-Id: Ia178a926e6f56a3ec9291250a22a66f212c30b14
Signed-off-by: Iliyan Malchev <malchev@google.com>

libhwcomposer/hwc_utils.cpp

diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 41a9c5a..a6a6f3e 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -60,6 +60,7 @@
     ctx->mMDP.hasOverlay = qdutils::MDPVersion::getInstance().hasOverlay();
     ctx->mMDP.panel = qdutils::MDPVersion::getInstance().getPanelType();
     ctx->mExtDisplay = new ExternalDisplay(ctx);
+    ctx->mLayerCache = new LayerCache();
     MDPComp::init(ctx);
 
     pthread_mutex_init(&(ctx->vstate.lock), NULL);
@@ -208,7 +209,7 @@
     int ret = 0;
 #ifdef USE_FENCE_SYNC
     struct mdp_buf_sync data;
-    int acquireFd[4];
+    int acquireFd[MAX_NUM_LAYERS];
     int count = 0;
     int releaseFd = -1;
     int fbFd = -1;
@@ -219,7 +220,8 @@
     for(uint32_t i = 0; i < list->numHwLayers; i++) {
         if((list->hwLayers[i].compositionType == HWC_OVERLAY ||
             list->hwLayers[i].compositionType == HWC_FRAMEBUFFER_TARGET) &&
-            list->hwLayers[i].acquireFenceFd != -1) {
+            list->hwLayers[i].acquireFenceFd != -1 &&
+            (list->hwLayers[i].flags & HWC_MDPCOMP)) {
             acquireFd[count++] = list->hwLayers[i].acquireFenceFd;
         }
     }
@@ -251,4 +253,71 @@
     return ret;
 }
 
+void LayerCache::resetLayerCache(int num) {
+    for(uint32_t i = 0; i < MAX_NUM_LAYERS; i++) {
+        hnd[i] = NULL;
+    }
+    numHwLayers = num;
+}
+
+void LayerCache::updateLayerCache(hwc_display_contents_1_t* list) {
+
+    int numFbLayers = 0;
+    int numCacheableLayers = 0;
+
+    canUseLayerCache = false;
+    //Bail if geometry changed or num of layers changed
+    if(list->flags & HWC_GEOMETRY_CHANGED ||
+       list->numHwLayers != numHwLayers ) {
+        resetLayerCache(list->numHwLayers);
+        return;
+    }
+
+    for(uint32_t i = 0; i < list->numHwLayers; i++) {
+        //Bail on skip layers
+        if(list->hwLayers[i].flags & HWC_SKIP_LAYER) {
+            resetLayerCache(list->numHwLayers);
+            return;
+        }
+
+        if(list->hwLayers[i].compositionType == HWC_FRAMEBUFFER) {
+            numFbLayers++;
+            if(hnd[i] == NULL) {
+                hnd[i] = list->hwLayers[i].handle;
+            } else if (hnd[i] ==
+                       list->hwLayers[i].handle) {
+                numCacheableLayers++;
+            } else {
+                hnd[i] = NULL;
+                return;
+            }
+        } else {
+            hnd[i] = NULL;
+        }
+    }
+    if(numFbLayers == numCacheableLayers)
+        canUseLayerCache = true;
+
+    //XXX: The marking part is separate, if MDP comp wants
+    // to use it in the future. Right now getting MDP comp
+    // to use this is more trouble than it is worth.
+    markCachedLayersAsOverlay(list);
+}
+
+void LayerCache::markCachedLayersAsOverlay(hwc_display_contents_1_t* list) {
+    //This optimization only works if ALL the layer handles
+    //that were on the framebuffer didn't change.
+    if(canUseLayerCache){
+        for(uint32_t i = 0; i < list->numHwLayers; i++) {
+            if (list->hwLayers[i].handle &&
+                list->hwLayers[i].handle == hnd[i] &&
+                list->hwLayers[i].compositionType != HWC_FRAMEBUFFER_TARGET)
+            {
+                list->hwLayers[i].compositionType = HWC_OVERLAY;
+            }
+        }
+    }
+
+}
+
 };//namespace