On Tuesday, June 26, 2012 5:14:45 pm Marius Strobl wrote: > Yes, it does but switching to positive decoding nevertheless is > problematic in this case. According to the PCI 2.3 specification, > a child wanting its addresses to be decoded subtractively needs > to provide special DEVSEL# behavior. It seems that it should work > for a bridge to actually positively decoding such transactions, > but I'm not familiar with the physical layer of PCI and thus not > sure. On the other hand, both the PCI-ISA and PCI-PCI bridges > in question are ALi/ULi crap and based on fun I had with their > chips in the past, I also wouldn't be surprised their again being > a magic bit in the configuration space needing to be set to make > this work. Unfortunately, I don't have a datasheet for this > M5249 PCI-PCI bridge. If we'd implement a tunable for changing > the decoding of subtractive bridges, the way to go would seem to > be to have it off by default in order to preserve pre-NEW_PCIB/ > r237008 as at this time it's unknown how many bridges are > affected. If you'd want to keep the new/current behavior by > default, introducing something like a PCIB_SUBTRACTIVE_FORCED > flag along a PCI_QUIRK_SUB_FORCED quirk in addition to a > tuneable defaulting to on probably would be a good idea.
Hmm. I'm fine with your original change going in then. I am not really sure what the right way to handle this is, and just leaving the windows alone on subtractive bridges is probably safest. -- John Baldwin _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
