Multiple mixer based multi cycle layer composition for power efficient display pipeline

In modern Graphic Architecture, display content is a mixture of different layers, analogous to a stack of cards which are mixed or composed pixel by pixel to form final display frame. Layer composition is handled by the GPU or an Overlay Hardware, either jointly or individually. While GPU can handle heavy composition, it results in higher power consumption as compared to Overlay. On the other hand, Overlay hardware is mostly constrained by the number of layers supported, causing dependence on GPU. Another issue with Overlay hardware is that many if its components are reserved for specific display operations such as external display support, and remain idle when such operations are not required. In this paper, we propose a technique which operates in multiple cycles to employ such under-utilized hardware components for the composition jobs. With this technique, the composition capability of mostly idle layer mixers can also be harnessed to handle more number of layers. The GPU load is thereby reduced resulting in less power consumption in the display pipeline while maintaining the normal display frame rate.