Messages in this thread | | | Date | Fri, 3 Dec 2004 15:59:27 -0600 | From | Terence Ripperda <> | Subject | Re: 2.6.10-rc2-mm4 |
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(sorry for breaking the email thread, I tried to grab the mbox archive for responding, but ftp.uwsg.iu.edu seems to be having problems with the mail archive).
in response to Alan Cox' voiced concerns from Tue Nov 30:
> That would also be a proprietary hook wouldn't it 8)
nvidia really isn't interested in proprietary hooks; such a hook really wouldn't be good for nvidia or the linux kernel. but we don't feel that a 32-bit zone is such a hook.
> beyond the supported open source hardware PCI-Express is the > non-AGPGART user and that is 64bit.
I assume you mean traditional pci in this case, but I remain confused. the pci spec calls for 32-bits of addressing, although there is an optional extension for 64-bit bus extension pins. I can't speak for other pci devices, but all of our pci devices are 32-bit.
additionally, the pci-express spec defines legacy and non-legacy devices. legacy devices are only required to address 32-bits, whereas non-legacy devices are required to handle 64-bit addresses.
> In the video space it's even stranger because DRI doesn't need it
I'm unclear how traditional pci video cards function without being able to allocate < 32-bit addresses for dma purposes. are the video cards you've tested 64-bit capable or is dma disabled? what about 32-bit cards? I'm afraid I don't understand how this isn't an issue.
> it seems a risky path because of the past problems trying to get > zone balancing working.
I certainly understand the concerns with this, although I was led to believe that recent 2.6 work made the zone balancing much less expensive. is that not the case?
> I can find users for a 512Mb or 1Gb DMA region
there was some brief discussion of this when we originally discussed 32-bit addressing issues, but I don't know if a satisfactory solution was reached. If a 1Gb region was prefered for this reason, that should satisfy nvidia's needs for 32-bit addressing, but I couldn't speak for any other device drivers.
for reference, the previous discussion was here:
http://www.uwsg.indiana.edu/hypermail/linux/kernel/0406.2/2093.html
Thanks, Terence
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