Messages in this thread | | | Subject | Re: DMA changes in 2.3.41 - how the f* do I get this working on ARM? | From | Jes Sorensen <> | Date | 31 Jan 2000 11:02:28 +0100 |
| |
>>>>> "David" == David S Miller <davem@redhat.com> writes:
David> From: Russell King <rmk@arm.linux.org.uk> Date: Sun, 30 Jan David> 2000 00:06:15 +0000 (GMT)
> I would have preferred to have heard about the extent of > these changes (and that the dma_cache_* macros were going to be > removed, along with my comments marking them with my initials) > before it was submitted.
David> For the actual transfers, you can do the dma_cache_*() calls in David> the pci_{un,}map_streaming() calls.
David> The only place you could possibly need it is for the IDE David> scatter list tables, and that would only be if you have _no_ David> mechanism to disable the CPU cache in the MMU, which I severely David> doubt.
Hmmm ok I just noticed this and I haven't read that DMA mapping document yet. I'll have to look at it to see how it affects PCI devices that are 64 bit address capable.
The one thing for the m68k is that we have very few machines with PCI, though we still suffer a lot from the DMA coherency problem on the busses we do have.
The place where this is a real problem is in drivers where data is shared between the adapter and the host CPU, for instance the 53c7xx driver. On the m68k we currently use a kernel_set_cachemode() function to change the caching of the page allocated for the shared structures, but thats a pretty non portable way of doing it. I would like to see something a get_free_cachecoherent_page() interface instead, what do you think of that?
Jes
- 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/
| |