On Fri, Mar 02, 2012 at 05:18:37PM -0500, John Baldwin wrote: > On Friday, March 02, 2012 4:45:52 pm Marius Strobl wrote: > > On Fri, Mar 02, 2012 at 08:38:05PM +0000, John Baldwin wrote: > > > Author: jhb > > > Date: Fri Mar 2 20:38:04 2012 > > > New Revision: 232403 > > > URL: http://svn.freebsd.org/changeset/base/232403 > > > > > > Log: > > > - Add a bus_dma tag to each PCI bus that is a child of a Host-PCI > > > bridge. > > > The tag enforces a single restriction that all DMA transactions must > > > not > > > cross a 4GB boundary. Note that while this restriction technically > > > only > > > applies to PCI-express, this change applies it to all PCI devices as > > > it > > > is simpler to implement that way and errs on the side of caution. > > > > Hrm, wouldn't it have been more appropriate to implement this in the > > Host-PCI bridges instead? Probably for anything but x86 this would > > allow to easily distinguish at least between PCI and PCI-Express capable > > bus hierarchies and would move the PAE workaround to the MD bits to > > where it belongs. > > The PAE workaround is dying as I've already fixed HEAD to make boundary > arguments > use a bus_addr_t. However, I committed it in this fashion so it can be MFC'd > since I can't merge the boundary KBI change. > > The reason I did not do this in the Host-PCI bridge drivers is that we would > have > to do this in umpteen different drivers, and all for a change that is > mandated by > the PCI spec and not specific to the various specs the Host-PCI bridge drivers > all cater to (OFW, ACPI, MPTable, various and sundry embedded platforms, > etc.). >
Well, on !x86 we don't have generic Host-PCI bridge drivers based on what you call specs here, but rather specific drivers for individual Host-PCI, Host-PCI-X and Host-PCI-Express chips. Whether the PCI* buses beneath these are enumerated using FDT, OFW etc. doesn't really matter in this context. Marius _______________________________________________ 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"
