[U-Boot] pci booting 460ex seems to hang at tlb entries

Ayman M. El-Khashab ayman at elkhashab.com
Tue Dec 2 01:20:10 CET 2008


Thanks for any pointers.

So here is my current setup, 2 460ex parts bussed together via the
PCI bus.  The master boots u-boot via flash, reserves some memory,
and boots linux.  A user process then maps that memory and loads a
"flash image" into it.  The PIM and POM registers on the master
and slave processor are then configured.  The slave is setup to 
enable bus mastering and then its boot is started.  I see all the
instructions being fetched across the PCI bus correctly (I've made
loops and things to confirm that everything is executed on the slave
properly).  As I follow the instructions across the PCI bus I see
it start at the usual location, then jump to FFFFF000 and start
going.  It makes it all the way to FFFFF29C and then nothing comes
across the PCI bus.  When I check the code to see where that is, it
is the configuration of the TLB entries in init.S (which is almost
exactly the same as the init.S for canyonlands).  It seems that I've
got something setup wrong and that is inhibiting the CPU from any
more fetches on the PCI bus.  The only TLB entry that I've changed
from the canyonlands is the very first one to the following:

tlbentry(CONFIG_SYS_BOOT_BASE_ADDR, SZ_16M, \
  CONFIG_SYS_BOOT_BASE_ADDR, 0xC, AC_R|AC_W|AC_X|SA_G) /* TLB 0 */

CONFIG_SYS_BOOT_BASE_ADDR is 0xFF000000
0xC is the space that according to the datasheet is the location
of the PCI space.  It is the same address that I am using for the
POMs so it at least behaves as expected for the initial part of
the boot.

I did not see anything else that I *knew* required modification but
I was a little unsure about the PCI space TLB entry.  Is there 
another place in the code I need to be modifying things?  This 
happens early so the choices look to be a limited as to what could
be wrong.  I've also tried the abatron, but it seems to misbehave
when using this boot mode.

Thanks,


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