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1676 tullio 1 
%----------------------------------------------------------------------------
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\chapter{The CPU frequency scaling library}
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%----------------------------------------------------------------------------
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This driver allow the application to change the CPU speed in order to reduce
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power consumption. After the driver initialization is possible to know the list
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of supported frequencies, the minimin and maximun allowed frequncy. Is possible
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to get and set the current frequecy and obtaind the deoretical value of the
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transition duration.
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%----------------------------------------------------------------------------
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\section{CPU Information utility}
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%----------------------------------------------------------------------------
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These functions allow the application to know informations about the CPU like
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manufacturer, model, capabilities, etc.
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\vspace{7mm}
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\begin{intest}
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CPU26\_INIT\index{CPU26\_init()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_init(void);}]
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\item [\textbf{Description:}] Initialize the driver and all internal structures. The
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function returns 0 if the procedure was succesfully, -1 otherwise.
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\end{description}
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\begin{intest}
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CPU26\_CLOSE\index{CPU26\_close()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_close(void);}]
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\item [\textbf{Description:}] It close the CPU driver.
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\item [\textbf{Return value:}] 0 if the operation is performed successfully; -1
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if the keyboard in not installed.
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\end{description}
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\begin{intest}
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CPU26\_INSTALLED\index{CPU26\_instaled()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_installed(void);}]
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\item [\textbf{Description:}] Return if the event debugger is actually installed.
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\item [\textbf{Return value:}] 0 if the module is installed; 1 otherwise.
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\end{description}
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\begin{intest}
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CPU26\_SHOWINFO\index{CPU26\_showinfo()}
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\end{intest}
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\begin{description}
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\item [\textbf{void CPU26\_installed(void);}]
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\item [\textbf{Description:}] Print the CPU informations retrived by the driver.
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\end{description}
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%----------------------------------------------------------------------------
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\section{CPU scaling functions}
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%----------------------------------------------------------------------------
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These functions allow to get/set parameter about the CPU frequency and its
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behavior. The low level must be initialized with the \texttt{CPU26\_init()}
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function before using scaling funtionalities.
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\vspace{7mm}
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\begin{intest}
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CPU26\_DVS\_INIT\index{CPU26\_DVS\_init()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_DVS\_init(void);}]
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\item [\textbf{Description:}] Initialize the driver and all internal structures. The
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function returns the CPU identifyer if that present DVS capabilities, -1
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otherwise.
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\end{description}
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\begin{intest}
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CPU26\_DVS\_CLOSE\index{CPU26\_DVS\_close()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_DVS\_close(void);}]
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\item [\textbf{Description:}] It close the CPU driver.
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\item [\textbf{Return value:}] 0 if the operation is performed successfully; -1
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if the driver in not installed.
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\end{description}
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\begin{intest}
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CPU26\_DVS\_INSTALLED\index{CPU26\_DVS\_instaled()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_DVS\_installed(void);}]
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\item [\textbf{Description:}] Return if the DVS driver is actually installed.
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\item [\textbf{Return value:}] The function returns the CPU identifyer if that
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present DVS capabilities, -1 otherwise.
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\end{description}
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\begin{intest}
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CPU26\_GET\_LATENCY\index{CPU26\_get\_latency()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_get\textbackslash{}\_latency(void);}]
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\item [\textbf{Description:}] Return the value of the latency time needed to change
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between two frequencies.
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\end{description}
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\begin{intest}
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CPU26\_GET\_MIN\_FREQUENCY,\index{CPU26\_get\_min\_frequency()}
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CPU26\_GET\_MAX\_FREQUENCY\index{CPU26\_get\_max\_frequency()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_get\_min\_frequency(void);}]
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\item [\textbf{int CPU26\_get\_max\_frequency(void);}]
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\item [\textbf{Description:}] Are used to obtain minumum and maximum allowed frequencies.
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\end{description}
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\begin{intest}
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CPU26\_GET\_CUR\_FREQUENCY\index{CPU26\_get\_cur\_frequency()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_get\_cur\_frequency(void);}]
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\item [\textbf{Description:}] Return the value of the actual frequency of the processor.
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\end{description}
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\begin{intest}
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CPU26\_SET\_FREQUENCY\index{CPU26\_set\_frequency()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_set\_frequency(int target, unsigned int relation);}]
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\item [\textbf{Description:}] Return
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\end{description}
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\begin{intest}
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CPU26\_GET\_FREQUENCIES\index{CPU26\_get\_frequencies()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_set\_frequency(int {*}freqs);}]
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\item [\textbf{Description:}] Return
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\end{description}
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\begin{intest}
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CPU26\_SHOW\_FREQUENCIES\index{CPU26\_show\_frequencies()}
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\end{intest}
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\begin{description}
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\item [\textbf{int CPU26\_show\_frequency(char {*}buff);}]
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\item [\textbf{Description:}] Return
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\end{description}