powerpc: ppc4xx: remove korat board support

[karo-tx-uboot.git] / doc / README.MPC866

diff --git a/doc/README.MPC866 b/doc/README.MPC866
index 1464a408ca0fc65e7859f763660e0d0291f4f048..4707cb7df7d6362ee2887085fd5e8291b33c96e9 100644 (file)
--- a/doc/README.MPC866
+++ b/doc/README.MPC866
@@ -1,19 +1,24 @@
 The current implementation allows the user to specify the desired CPU
 clock value, in MHz, via an environment variable "cpuclk".
 
-Three compile-time constants are used:
+Four compile-time constants are used:
 
-       CFG_866_OSCCLK            - input quartz clock
-       CFG_866_CPUCLK_MIN        - minimum allowed CPU clock
-       CFG_866_CPUCLK_MAX        - maximum allowed CPU clock
-       CFG_866_CPUCLK_DEFAULT    - default CPU clock value
+       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 note that for now the new clock-handling code has been enabled
-for the TQM866M board only, even though it should be pretty much
-common for other MPC859 / MPC866 based boards also. Our intention
-here was to move in small steps and not to break the existing code
-for other boards.
+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.