Hi all,
Once I'd written the email on this subject to the U-Boot list, I figured it was starting to sound like a Freescale support request, so I submitted one too. Here's their response:
"Actually, snooping occurs inside MPC8349 device. Besides e300 core, other possible masters are: PCI1, PCI2, DMA, TSEC1, TSEC2, USB, Ecnryption engine."
So, it does sound like there are devices internal to the MPC8349EA that are monitoring the e300 core gbl# signal, and hence the M-bit would need to be set in the BAT entries.
FYI:
- The M-bit is set for the BAT entries for: DDR, PCI memory, SDRAM, stack-in-dcache, and Flash)
- The M-bit is not set for: PCI I/O, IMMRs, and BCSRs these are cache inhibited and guarded.
And this list pretty much makes sense. The exception would be the stack-in-dcache, since there is no external memory associated with the stack-in-dcache trick.
Trying to understand the stack-in-dcache trick was what what started all this ... but, I guess in that case, having the M-Bit set in the BAT entry doesn't really matter, since nothing is (or should be) snooping that address anyway.
Sorry for the 'noise' :)
Cheers, Dave