Pavel Bartusek wrote:

I thing that system clock and bus clock can be different (in terminology
of the MPC855T user manual)

MPC855T manual, section Clocks and Power Control:
"
GCLK1C/GCLK2C - Basic clocks supplied to the core, the data and
instruction caches, and MMUs.
GCLK1_50/GCLK2_50 - Optionally divided versions of GCLK1/GCLK2, which
are used to clock the GPCM and UPM in the memory controller and to
provide the CLKOUT output for the external bus.

Notice in all of the descriptions there is no definition of "system clock."
I carefully read all of the 8xx manuals, and there are a few references
to "system clocks", especially around power management and frequency
control.  There are a couple of references to peripheral clocks being
derived from a "system clock", which from the context appears to be the
same as the core clock, not the CLKOUT that would be supplied to the rest
of the "system."

It appears the MII clock must be derived from the core clock speed, so
my code change suggestion the other day was wrong. :-)

quoted

quoted

  (((bd->bi_intfreq + (2 * 2500000 - 1 )) / 2500000 / 2) & 0x3F) << 1;

OK. It is more correct.

try this (since the problem is the divisor register truncation):

(((((bd->bi_intfreq + 500000) / 2500000) + 1) / 2 ) & 0x3F ) << 1;

Thanks.


	-- Dan


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