Re: How to change Bus speed for MPC8xx CPU

In message [ref] you wrote:

 cpu MHz : 100
 bus MHz : 50

 My board is runnig from external clock of 10M and boot monitor
 has parameter called mulitplier which is equal to 10.

10 * 10 MHz = 100 MHz CPU Clock.

100 MHz CPU clock / 2 (see EBDF bits in SCCR) = 50 MHz bus clock

 I need to slow bus speed to 40MHz and from 862 data sheet I see
 what this can be done by writing to internal registers of clock
 engine.

Try changing the multiplicator factor to 8, so you get 80 MHz  CPU  /
40 MHz bus clocks.

 My question is how kernel deal with it. Where and how clock are configured
 and how can I change it. Is it done on the boot time by kernel boot loader ?

The kkernel does not deal with this at all. It  receives  information
about the system clocks from the boot loader.

 Maybe you can apoint me to the source in kernel where clock parameters
 are configured. IMHO it should be somwhere in boot.

This is done in the boot loader.


Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
A person with one watch knows what time it  is;  a  person  with  two
watches is never sure.                                       Proverb

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