[U-Boot-Users] 859/866 clock issues

Wolfgang Denk wd at denx.de
Mon Oct 20 01:16:17 CEST 2003


in message <20031018002619.GB325 at zumanetworks.com> you wrote:
> two minor things on the 859/866
> 1) measure_gclk() is very inaccurate. Better to use the plprcr and
> CFG_8XX_XIN (which MUST BE 10MHz for that cpu) to derive the "real" bus
> clock.

What do you mean by "very inaccurate" - the intention of the function
(as documented) is to measure the "Approx. GCLK frequency in Hz". How
bad is "very inaccurate" in your case?

> 2) the 859/866 does NOT support external speeds higher than 66MHz,
> so if cpu_clk is greater, EBDF01 MUST BE USED IN CFG_SCCR

I think this is the case for ALL MPC8xx processors  so  far.  I  have
never seen one which would allow a bus clock > 66 MHz.

> I have a patch for 1, but i no longer have my 859/866 eval board

Maybe you can share it anyway.

> I have no patch for 2, but eventually we should come up with some sort
> of solution; the 859/866 is almost always configured to run faster than
> 66MHz.

I don't see why a patch should be  needed  here.  This  is  a  simple
matter of getting your board config file right, isn't it?

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
"Infidels in all ages have battled for the rights of man, and have at
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