Samsung S5PC110, Manual

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S5PC110_UM 5 INTELLIGENT ENERGY MANAGEMENT
5-12
5.2.2.3 Running the Standard Event Handlers
The standard event handlers are run periodically by the IEM kernel.
When the IEM kernel determines that it must run the standard event handlers, there are typically a number of
outstanding system events in the event queue, that have not yet been processed by the standard event handlers.
Starting with the oldest event, the IEM kernel processes each event in turn by enabling pre-emption, and then
running the standard event handlers.
The standard event handlers are run in a very similar way to the fast event handlers. For each policy, the IEM
kernel determines whether its standard event handler recognizes the system event. If so, the IEM kernel runs the
standard event handler, passing it pointers to the IEM kernel data structures that include:
•
The system event structure describing the event
•
The IEM block describing the task that triggered the system event.
The standard event handler then processes the event, analyzing the data in the IEM kernel data structures and
any data that was stored by the fast event handler to determine the optimum performance level. The analysis that
the standard event handler performs is usually very different to that performed by the fast event handler of the
same policy. This is because the standard event handler is working on historical data. Also, the standard event
handler is pre-emptable, and so can spend longer analyzing the data without impacting system responsiveness. It
can therefore use more complex algorithms, such as decaying weighted averages.
When the final outstanding event in the queue is processed, the standard event handlers can request a
performance level. The IEM kernel then combines any performance requests that the standard event handlers are
making, and sets the resulting performance level using the IEM HAL.