Re: Problem with framebuffer mmap on platforms with large addressing

On Tue, Mar 20, 2012 at 9:40 AM, Benjamin Herrenschmidt
[off-list ref] wrote:

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That is interesting! Are those patches published or otherwise available
somewhere? We are also very interested in enabling Canyonlands
with Radeon KMS!

You will run into additional problems with 460 due to the fact that it's
not cache coherent for DMA. Tony patches don't address that part of the
problem (they were used on a 476 based platform).

Hmm. Could you please spill a little bit more of details? Also are those patches
for 476 merged or present somewhere?

Well, DMA on 46x isn't cache coherent. The DRM plays interesting games
with mapping/unmapping pages for DMA by the chip and I don't think we
have the right hooks to do the appropriate cache flushing on these guys,
but Tony might be able to comment, I don't know whether he tried or not.

On the other hand 476 has fully cache coherent DMA so the only problem
there is the >32-bit physical address space.

As for the patches, you'll have to wait for Tony to respond (I'll poke
him locally).

Any news on these patches? A dirty and "not for the upstream yet" version
would be sufficient for me for now.

Cheers,
Ben.

-- 
With best wishes
Dmitry