Messages in this thread | | | From | Jay.Estabrook@digital ... | Subject | Re: > 1GB on alpha. Patch to 1TB? | Date | Sun, 14 Mar 1999 11:02:18 -0500 |
| |
>>> Jakub Jelinek said: > > There is something in the sparc tree, which is used also for sun4c and sun4d > (where there is only 64MB of DMA per board, so one has to remap DMA areas > during runtime). > Besically, each driver before it starts doing dma uses some function which > translates virtual address + length to dma address and allocates it, then > after the dma the driver has to release it again.
This is a technique that would work on the Alphas as well, but as noted above, it *does* require driver modifications to manage the resource correctly.
On Alpha, in addition to the direct-map DMA windows which are currently used, one can define what we call "scatter-gather" DMA windows. The range of PCI addresses that fall into one of these windows are re-directed to host memory via a page table, where the address in a PTE can be *any* page in the possible installed memory - no bounce buffers needed... :-)
> Martin Mares and myself are considering this as part of the new buses > interface we plan for 2.3. The Ultra port supports even now huge amounts of > memory, but uses bounce buffers for that. I plan to change it in early 2.3.
Great! Keep us posted with your progress.
--Jay++
------------------------------------------------------------------------------- American Non Sequitur Society: we don't make sense, but we do like pizza...
Jay A Estabrook Alpha Motherboards - LINUX Project Compaq Computer Corporation (508) 841-3241 or (DTN) 237-3241 334 South Street, Shrewsbury, MA 01545 Jay.Estabrook@digital.com -------------------------------------------------------------------------------
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |