GPU has two pixel processors which can be powered down when not in use. If the end application is not using GPU, then GPU can be shut down completely. The Clock can be gated, Pixel Processors can be power gated, and the logic can be held in reset. This will provide a huge power saving opportunity of around 118mW (@500MHz).
When GPU driver is enabled in Linux, the runtime PM is automatically taken care and the pixel processors are powered down when GPU is idle. However, in systems where the GPU driver is not loaded, GPU power domains can be powered down explicitly by using PM debugfs interface as shown below or using the boot time PM technique.