On Fri, Jun 24, 2011 at 1:52 PM, Matthew Wilcox <matthew@xxxxxx> wrote: > On Fri, Jun 24, 2011 at 09:15:24AM -0700, Jesse Barnes wrote: >> On Thu, 23 Jun 2011 23:16:57 -0500 >> Xianghua Xiao <xiaoxianghua@xxxxxxxxx> wrote: >> >> > We're using a ARM that only has 256MB PCI space, however I have a PCI >> > device that has a BAR(for its own memory) that is 512MB, for ARM to >> > allocate it I modified the BAR size on the device to 128MB(there are >> > other PCI devices to use portion of the rest 128MB) >> > >> > I can modify the BAR at run time, is it ok for me to change the BAR >> > address to address all the 512MB on PCI device? The PCI memory address >> > ARM allocates at boot time can stay the same, but the BAR will be >> > changed to re-map to all the 512MB space on the PCI device(each time >> > for 128M), is this do-able? >> >> Sounds pretty hackish, but as long as you can deal with the decode >> priorities for the address space on your platform (e.g. make sure your >> 512M device doesn't start decoding cycles meant for RAM or some other >> fixed resource region) then doing the above should be possible. > > I doubt it's possible ... it'd only be possible if the 256MB PCI address > space were not aligned to a 256MB boundary. And nobody builds systems > like that. > > -- > Matthew Wilcox Intel Open Source Technology Centre > "Bill, look, we understand that you're interested in selling us this > operating system, but compare it to ours. We can't possibly take such > a retrograde step." > can you explain a little more on this, the 256MB is aligned of course, why does the modifiable BAR needs an unaligned pci mem space? Thanks, Xianghua -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
