[Mesa-dev] [PATCH 09/13] r300g, r600g, radeonsi: add support for ARB_buffer_storage

[Michel Dänzer]

On Don, 2014-01-30 at 23:46 +0100, Fredrik Höglund wrote:
> On Thursday 30 January 2014, Marek Olšák wrote:
> > From: Marek Olšák <marek.olsak at amd.com>
> > 
> > All GTT memory mappings are coherent and therefore can be persistent.
> 
> As we discussed on IRC, I think there should be a comment somewhere
> explaining that VRAM mappings are uncached, so the memory_barrier
> implementations don't need to do anything for those.

VRAM is mapped uncacheable by the CPU, but there is an HDP cache which
must be flushed to ensure coherency between the CPU and GPU. So I
suspect memory_barrier actually needs to flush the HDP cache for VRAM.

I'm wondering about GTT mappings on AGP as well. I think we're using CPU
write-combining for those, so we probably need to flush the
write-combining buffers?


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer