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| author |   Yang Zhang <yang.z.zhang@intel.com> | 2015-08-28 09:58:54 +0800 |
|---|---|---|
| committer | Yang Zhang <yang.z.zhang@intel.com> | 2015-09-01 12:44:00 +0800 |
| commit | e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb (patch) | |
| tree | 66b09f592c55df2878107a468a91d21506104d3f /qemu/roms/u-boot/doc/README.MPC866 | |
| parent | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (diff) | |
Add qemu 2.4.0
Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Diffstat (limited to 'qemu/roms/u-boot/doc/README.MPC866')
| -rw-r--r-- | qemu/roms/u-boot/doc/README.MPC866 | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/qemu/roms/u-boot/doc/README.MPC866 b/qemu/roms/u-boot/doc/README.MPC866 new file mode 100644 index 000000000..4707cb7df --- /dev/null +++ b/qemu/roms/u-boot/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. |