Date: Fri, 2 Mar 2012 17:18:37 -0500 From: John Baldwin <jhb@freebsd.org> To: Marius Strobl <marius@alchemy.franken.de> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r232403 - in head/sys: dev/acpica dev/cardbus dev/pci powerpc/ofw sparc64/pci Message-ID: <201203021718.38092.jhb@freebsd.org> In-Reply-To: <20120302214551.GB1635@alchemy.franken.de> References: <201203022038.q22Kc5vd046376@svn.freebsd.org> <20120302214551.GB1635@alchemy.franken.de>
next in thread | previous in thread | raw e-mail | index | archive | help
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.). -- John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201203021718.38092.jhb>