Messages in this thread |  | | | Date | Mon, 18 Aug 2003 11:15:22 -0400 | | From | Pete Zaitcev <> | | Subject | Re: [PATCH] RFC: kills consistent_dma_mask |
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> From: Krzysztof Halasa <khc@pm.waw.pl> > Date: 18 Aug 2003 00:34:17 +0200
> It's unneeded (it can be easily done in a driver, should a need arrive, > without polluting the PCI subsystem) and is not supported by "DMA" API.
Are you talking about doing tripple calls, e.g.
pci_set_dma_mask(pdev, 0xFFFFFFFF); foo = pci_alloc_consistent(pdev, size, &handle); // Restore for upcoming streaming allocations pci_set_dma_mask(pdev, 0xFFFFFFFFFFFFFFFF); Possibly Jes considered that alternative and decided that it did not allow for sufficient performance.
> It isn't even implemented on most platforms - only x86_64 and ia64 have > support for it, while on the remaining archs using it according to the > docs (with non-default value) could mean Oops or something like that.
Before you go for that, I'd rather see you implementing the double/tripple calls in drivers, check for effects, THEN go for removal of the mask. If you cannot do it, plea SGI people to test it on SN-2 for you (or same for Intel Tiger box).
> This patch doesn't actually change any current kernel behaviour.
Sure it does. It blows all non-mmu ia64 out of the water.
The consistent mask looks a little distasteful to me, and I think it should not buy us performance because consistent allocations are not supposed to be fast. They are bad, but what you are doing is worse: you are trying to ruin the day of legitimate users. Please, be reasonable. Get SGI buy-in and come back.
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