Samsung S5PC100, User Manual

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S5PC100 USER’S MANUAL (REV1.0) INTELLIGENT ENERGY MANAGEMENT
2.5-9
2.2 IEM SYSTEM OPERATION
Loading and starting the software
At an appropriate stage of system boot-up, the OS loads and initializes the modules that contain the IEM
software:
•
on most platforms, the module loader automatically runs the initialization code for a module (if any)
•
otherwise, the OS (or a driver) must call the initialization code itself.
This initialization code performs much of the set up for the IEM software. For example:
•
the code in the IEM HAL sets up and configures the performance scaling hardware
•
the code in the Control component loads the Comms driver that it uses to communicate with the IEM kernel.
The OS then configures the IEM kernel by issuing commands to the Control component. The Control component
encodes these commands as messages, and uses the Comms driver to send them to the IEM kernel. These
control messages:
•
start the policies, so that they are ready to use
•
optionally:
♦
configure the IEM activities that are traced
♦
enable tracing.
Finally, the OS issues a command to start the IEM kernel. When the IEM kernel receives the corresponding
control message, it:
1. Allocates memory for the event queue, and initializes it.
2. Allocates memory for the IEM blocks, and initializes them.
3. Registers the kernel hooks that the OS calls whenever a system event occurs.
2.2.1 Handling system events
When an event occurs that might influence the optimum performance level, the OS calls the appropriate kernel
hook in the IEM kernel:
•
The New Task hook is called whenever a new task is created. This hook generates a New Task system event
for the new task that has just been created.
•
The Exit hook is called whenever a task is about to exit. This hook generates a Task Exit system event for the
exiting task.
•
The Task Switch hook is called whenever the OS switches from one task to another. This hook generates two
system events:
♦
a Task Schedule Out system event for the previous task that has just been switched out
♦
a Task Schedule In system event for the next task that is being switched in.
•
The User Input hook is called whenever a task receives user input. This hook generates a User Input system
event for the task that is receiving input.
When a kernel hook generates an system event, it determines whether any event handlers recognize the system
event. If so, it: