3,260
edits
Changes
m
→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 time (due to the fact that it's the kernel that schedules its processes). Having a configurable CPU governor is a standard feature of Linux kernel, that can be found on PCs and laptops. The Kernel changes A8 frequency/voltage in accordance with user settings.
All the other stuff subsystems (DSP, HDVICP2 and CORE) are not managed directly from by the kernel (e.g. dual M3 runs run their own independent RTOS), for this reason it cannot choose which is the optimal working set from a PM point of view. It's userspace application responsibility to choose Choosing the correct OPP ('''Operating Performance Points) is userspace application''') s responsibility to reach a given obtain the desired 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.
