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→Runtime Power Management Support
The main difference between the two is that the Linux kernel itself knows pretty well how much the A8 is loaded at a given point in time (due the fact that it's the kernel the one that schedule the kernel and userspace processes). Having a configurable CPU governor is a standard feature of Linux kernel, that can be found on PC/laptop too. Accordingly to user settings, the Kernel changes A8 frequency/voltage on it's own.
All the other stuff (DSP, HDVICP2 and CORE) are not managed directly from the kernel (e.g. dual M3 runs their own independent RTOS), for this reason it cannot choose which is the optimal working set from PM point of view. It's userspace application responsibility to choose the correct OPP ('''Operating Performance Points''') to reach a given result (e.g. Full-HD H264 encoding vs 720p H264 decoding).
This is even more true when considering video management applications: in this application runtime frequency scaling is critical because computational load is dependent on data stream and can change very quickly. What is usually done in this situation is to use a sub-optimal configuration that can handle the ''worst'' stream input without loosing frames and without wasting too much power. For this reason A8 too can be configured statically with OPP and thus disabling standard Linux governor support.
