Linux 2.6.10-rc3 8xx: debugging (over-writing) content of b d_in fo structure in the kernel booting code

John W. Linville linville at
Wed Jan 19 07:29:15 EST 2005

On Tue, Jan 18, 2005 at 02:08:19PM -0500, Povolotsky, Alexander wrote:
> My board is using:
>         bd->bi_intfreq = 50000000;
>         bd->bi_busfreq = 50000000;
> While RPX-Lite is using
>         bd->bi_intfreq = 48000000;
>         bd->bi_busfreq = 48000000; 
> Is this what makes RPX-Lite work and my (MPC 880) not ?

That, of course, depends on which value is correct for your
board... :-)

When I mentioned in one of our (possibly off-line) exchanges that
_slightly_ incorrect clock speeds might explain how you get a few good
characters from the serial port before you get all that garbage, this
is the kind of descrepancy I was suggesting.  There may be enough
"slop" in the timings of the relatively slow serial port to make
48MHz and 50MHz "close enough" for a few characters.

So, what is the correct number for your board?  Do you know how to
identify an oscillator?  They have a bit of a 'tin can' look to them.
Find the one closest to the CPU on the board, and see what number is
on it.

John W. Linville
linville at

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