I have an application I've tested on several i.mx6 boards (duallite and qxd) running yocto jethro (with and without the latest freescale upstream patches), and I think we're hitting a GPU and/or DDR bandwidth limit somehow.
My very simple qt5.5/qml app launches fullscreen at 1920x1080 @60Hz and simply shows a single untextured rotating rectangle on a black background and benchmarked it at 60 fps. I then added a background image (keeping the rectangle untextured), and immediately the framerate dropped to 50fps. Adding a simple webpage (via a webengine instance) drops it to 30 fps. In reality, our app needs to run a few webengine instances (one big "master" instance fullscreen and several smaller ones), but we're unable to achieve over 20 fps, and that's without any kind of video or advanced HTML5 transitions or effects.
Is the expected performance level of this chip? I've seen numerous demos that appear to combine lots of media types and play through smoothly, but so far have not been able to reproduce that at 1080p (things are of course much better at 720p).