Scott,
Thanks for that - you're right - redboot has the wrong crystal frequency
in the cdl for our board.
Cheers,
Richard.
Scott Wood wrote:
On Mon, Aug 18, 2008 at 07:52:12AM -0400, [EMAIL PROTECTED] wrote:
We've got an 8347 based board very similar to the A&M asp8347. Core clock
is 400MHz. Bus clock is 266666666Hz.
According to the data sheet for the 8347, the decrementer clock runs at a
quarter of the rate of the bus clock. I have two questions:
In arch/powerpc/boot/redboot-83xx.c, the timebase clock is passed to
dt_fixup_cpu_clocks() as bi_busfreq / 16. If I leave it like this, my
system clock runs approximately 4 times too fast.
Can anyone point me in the direction of an explanation for the div by 16
rather than 4?
It's a bug, which I pointed out here:
http://ozlabs.org/pipermail/linuxppc-dev/2008-June/058704.html
If I change the call to dt_fixup_cpu_clocks so that bi_busfreq/4 is passed
in, then the clock runs more accurately. However, its still not correct.
This gives a decrementer frequency of 66666666Hz, but if I hard code the
value to 66000000Hz, the clock runs accurately.
Can anyone shed any light on why the value passed in by the boot loader
(redboot) seems to be inaccurate.
Redboot probably has the wrong crystal frequency hardcoded.
-Scott
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