Messages in this thread | | | Subject | Re: Kernel virtual memory? | Date | Thu, 07 Aug 1997 20:57:25 +0800 | From | Stephen Williams <> |
| |
davem@jenolan.rutgers.edu said: > On Sparc all DMA on SBUS is based on virtual addresses. Each SBUS > has a dedicated "IOMMU" tlb which performs the va-->pa translations.
If I recall, that only applies to a small region in lower memory. You are talking about vdma and I believe it was only the low meg or something silly.
Not ALL dma uses the vdma, just the DMA addresses within the vdma region. Furthermore, there is a single IOMMU for all the devices on the SBus, getting you right back to the precious resource problem.
(Way back when I was involved with writing a SunOS driver for a board my cousin built, that did direct video to a printer. I think we concluded that scatter-gather was more practical.) -- Steve Williams steve@icarus.com steve@picturel.com
"The woods are lovely, dark and deep. But I have promises to keep, And lines to code before I sleep, And lines to code before I sleep."
| |