Samsung S5PC100, User Manual, Page: 282 / 1863

INTELLIGENT ENERGY MANAGEMENT S5PC100 USER’S MANUAL (REV1.0)
2.5-10
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creates a structure describing the system event
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ensures that there is an IEM block describing the corresponding task
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runs the fast event handlers to process the system event.
The kernel hook then determines whether any standard event handlers recognize the system event. If so, the
kernel hook adds the event to the event queue, for subsequent processing by the standard event handlers.
The kernel hook finally ensures that, if there are any system events in the event queue, the standard event
handlers run within a given period.
2.2.2 Running the fast event handlers
The fast event handlers are run from the kernel hooks whenever a system event occurs.
For each policy, the IEM kernel determines whether its fast event handler recognizes the system event. If so, the
IEM kernel runs the fast event handler, passing it pointers to the IEM kernel data structures that include:
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the system event structure describing the event
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the IEM block describing the task that triggered the system event.
The fast event handler then processes the event. Typical uses of the fast event handler include:
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Recognizing a task that requires an immediate change in performance level, and requesting that performance
level. The fast event handler might recognize:
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a specific task, such as a movie player
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a type of task, such as real-time tasks, or tasks that are receiving user input.
If necessary, the fast event handler can get further information about the task by making calls to the OS layer API.
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Storing policy-specific information about the current state of the task or the system, for later processing by the
standard event handler of the same policy. The fast event handler might get this information by making calls
to the IEM HAL or OS layer APIs. It typically stores this information in arrays of memory that are allocated by
the initialization function of the policy.
When the fast event handlers have been run, the IEM kernel then combines any performance requests that the
fast event handlers are making, and sets the resulting performance level using the IEM HAL.
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:
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the system event structure describing the event
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the IEM block describing the task that triggered the system event.