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

[Marek Olšák]

I think we always flush the HDP cache after (before?) command submission.

This patch adds nothing new to the drivers - we have always had
persistent buffer mappings for all buffers and it has always worked.
The only thing this does is that persistent mappings are now also
supported by Gallium and OpenGL.

If there is a missing cache flush somewhere, the new
ARB_buffer_storage piglit test will show it.

Marek

On Fri, Jan 31, 2014 at 2:04 AM, Michel Dänzer <michel at daenzer.net> wrote:
> 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
>