Messages in this thread | | | Date | Tue, 3 Jun 2008 08:21:46 +0300 | From | Muli Ben-Yehuda <> | Subject | Re: [PATCH -mm] x86 calgary: fix handling of devces that aren't behind the Calgary |
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On Sat, May 31, 2008 at 01:31:33PM +0900, FUJITA Tomonori wrote:
> The calgary code can give drivers addresses above 4GB which is very > bad for hardware that is only 32bit DMA addressable: > > http://lkml.org/lkml/2008/5/8/423 > > This patch tries to fix the problem by using per-device > dma_mapping_ops support. This fixes the calgary code to use swiotlb > or nommu properly for devices which are not behind the > Calgary/CalIOC2. > > With this patch, the calgary code sets the global dma_ops to swiotlb > or nommu, and the dma_ops of devices behind the Calgary/CalIOC2 to > calgary_dma_ops. So the calgary code can handle devices safely that > aren't behind the Calgary/CalIOC2.
This seems a little backward to me. I thought we were going to get rid of the global dma_ops? If not, assuming going through the global one would be more efficient, Calgary should be the global one and nommu/swiotlb should be used on devices that do not have translation enabled. The reason why is that the majority of devices on a Calgary system, assuming Calgary is in use, will have translation enabled.
In general the patch looks good, barring the point above. We'll give it a spin on some Calgary/CalIOC2 machines.
Cheers, Muli
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