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| author |   Angelos Mouzakitis <a.mouzakitis@virtualopensystems.com> | 2023-10-10 14:33:42 +0000 |
|---|---|---|
| committer | Angelos Mouzakitis <a.mouzakitis@virtualopensystems.com> | 2023-10-10 14:33:42 +0000 |
| commit | af1a266670d040d2f4083ff309d732d648afba2a (patch) | |
| tree | 2fc46203448ddcc6f81546d379abfaeb323575e9 /roms/u-boot-sam460ex/doc/README.MPC866 | |
| parent | e02cda008591317b1625707ff8e115a4841aa889 (diff) | |
Change-Id: Iaf8d18082d3991dec7c0ebbea540f092188eb4ec
Diffstat (limited to 'roms/u-boot-sam460ex/doc/README.MPC866')
| -rw-r--r-- | roms/u-boot-sam460ex/doc/README.MPC866 | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/roms/u-boot-sam460ex/doc/README.MPC866 b/roms/u-boot-sam460ex/doc/README.MPC866 new file mode 100644 index 000000000..4707cb7df --- /dev/null +++ b/roms/u-boot-sam460ex/doc/README.MPC866 @@ -0,0 +1,24 @@ +The current implementation allows the user to specify the desired CPU +clock value, in MHz, via an environment variable "cpuclk". + +Four compile-time constants are used: + + CONFIG_8xx_OSCLK - input quartz clock + CONFIG_SYS_8xx_CPUCLK_MIN - minimum allowed CPU clock + CONFIG_SYS_8xx_CPUCLK_MAX - maximum allowed CPU clock + CONFIG_8xx_CPUCLK_DEFAULT - default CPU clock value + +If the "cpuclk" environment variable value is within the CPUCLK_MIN / +CPUCLK_MAX limits, the specified value is used. Otherwise, the +default CPU clock value is set. + +Please make sure you understand what you are doing, and understand +the restrictions of your hardware (board, processor). For example, +ethernet will stop working for CPU clock frequencies below 25 MHz. + +Please note that the new clock-handling code is enabled if +CONFIG_8xx_CPUCLK_DEFAULT is defined. Since this mechanism supports +only MPC866 and newer CPUs, this constant MUST NOT be defined for +MPC823/850/860/862 series. The clock generation algorithm for older +chips is different and has not been implemented yet. If you need it, +your patch is welcome. |