hwc: Avoid MDP composition with alpha scaling

MDP4 supports scaling with alpha, only in RGB pipes.
In some cases this scaling happened with video pipes.
We now fall back to GLES composition for layers that have
alpha and need scaling.

Change-Id: I084355bad1cdb17c7308077b56006c59e75d2042
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Bug: 7648647

libhwcomposer/hwc_mdpcomp.cpp

@@ -273,6 +273,11 @@ bool MDPComp::isDoable(hwc_context_t *ctx, hwc_display_contents_1_t* list) {
         return false;
     }
 
+    if(ctx->listStats[HWC_DISPLAY_PRIMARY].needsAlphaScale) {
+        ALOGD_IF(isDebug(), "%s: frame needs alpha downscaling",__FUNCTION__);
+        return false;
+    }
+
     //FB composition on idle timeout
     if(sIdleFallBack) {
         sIdleFallBack = false;

libhwcomposer/hwc_utils.cpp

@@ -110,6 +110,25 @@ void dumpLayer(hwc_layer_1_t const* l)
           l->displayFrame.bottom);
 }
 
+static inline bool isAlphaScaled(hwc_layer_1_t const* layer) {
+    int dst_w, dst_h, src_w, src_h;
+
+    hwc_rect_t displayFrame  = layer->displayFrame;
+    hwc_rect_t sourceCrop = layer->sourceCrop;
+
+    dst_w = displayFrame.right - displayFrame.left;
+    dst_h = displayFrame.bottom - displayFrame.top;
+
+    src_w = sourceCrop.right - sourceCrop.left;
+    src_h = sourceCrop.bottom - sourceCrop.top;
+
+    if(((src_w != dst_w) || (src_h != dst_h))) {
+        if(layer->blending != HWC_BLENDING_NONE)
+            return true;
+    }
+    return false;
+}
+
 void setListStats(hwc_context_t *ctx,
         const hwc_display_contents_1_t *list, int dpy) {
 
@@ -118,10 +137,11 @@ void setListStats(hwc_context_t *ctx,
     ctx->listStats[dpy].yuvCount = 0;
     ctx->listStats[dpy].yuvIndex = -1;
     ctx->listStats[dpy].skipCount = 0;
+    ctx->listStats[dpy].needsAlphaScale = false;
 
     for (size_t i = 0; i < list->numHwLayers; i++) {
-        private_handle_t *hnd =
+        hwc_layer_1_t const* layer = &list->hwLayers[i];
-            (private_handle_t *)list->hwLayers[i].handle;
+        private_handle_t *hnd = (private_handle_t *)layer->handle;
 
         if(list->hwLayers[i].compositionType == HWC_FRAMEBUFFER_TARGET) {
             continue;
@@ -130,6 +150,9 @@ void setListStats(hwc_context_t *ctx,
             ctx->listStats[dpy].skipCount++;
         }
 
+        if(!ctx->listStats[dpy].needsAlphaScale)
+            ctx->listStats[dpy].needsAlphaScale = isAlphaScaled(layer);
+
         if (UNLIKELY(isYuvBuffer(hnd))) {
             ctx->listStats[dpy].yuvCount++;
             ctx->listStats[dpy].yuvIndex = i;
@@ -137,6 +160,7 @@ void setListStats(hwc_context_t *ctx,
     }
 }
 
+
 static inline void calc_cut(float& leftCutRatio, float& topCutRatio,
         float& rightCutRatio, float& bottomCutRatio, int orient) {
     if(orient & HAL_TRANSFORM_FLIP_H) {

libhwcomposer/hwc_utils.h

@@ -75,6 +75,7 @@ struct ListStats {
     //Video specific
     int yuvCount;
     int yuvIndex;
+    bool needsAlphaScale;
 };