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The current implementation allows the user to specify the desired CPU
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clock value, in MHz, via an environment variable "cpuclk".
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Three compile-time constants are used:
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CFG_866_OSCCLK - input quartz clock
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CFG_866_CPUCLK_MIN - minimum allowed CPU clock
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CFG_866_CPUCLK_MAX - maximum allowed CPU clock
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CFG_866_CPUCLK_DEFAULT - default CPU clock value
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If the "cpuclk" environment variable value is within the CPUCLK_MIN /
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CPUCLK_MAX limits, the specified value is used. Otherwise, the
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default CPU clock value is set.
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Please make sure you understand what you are doing, and understand
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the restrictions of your hardware (board, processor). For example,
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ethernet will stop working for CPU clock frequencies below 25 MHz.
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Please note that for now the new clock-handling code has been enabled
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for the TQM866M board only, even though it should be pretty much
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common for other MPC859 / MPC866 based boards also. Our intention
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here was to move in small steps and not to break the existing code
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for other boards.
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