Re: Tegra DRM device tree bindings

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 06/28/2012 05:12 AM, Thierry Reding wrote:
> On Wed, Jun 27, 2012 at 05:59:55PM +0200, Lucas Stach wrote:
>> Am Mittwoch, den 27.06.2012, 16:44 +0200 schrieb Thierry Reding:
...
>>> In the ideal case I would want to not have a carveout size at
>>> all. However there may be situations where you need to make
>>> sure some driver can allocate a given amount of memory. Having
>>> to specify this using a kernel command-line parameter is
>>> cumbersome because it may require changes to the bootloader or
>>> whatever. So if you know that a particular board always needs
>>> 128 MiB of carveout, then it makes sense to specify it on a
>>> per-board basis.
>> 
>> If we go with CMA, this is a non-issue, as CMA allows to use the
>> contig area for normal allocations and only purges them if it
>> really needs the space for contig allocs.
> 
> CMA certainly sounds like the most simple approach. While it may
> not be suited for 3D graphics or multimedia processing later on, I
> think we could use it at a starting point to get basic framebuffer
> and X support up and running. We can always move to something more
> advanced like TTM later.

I thought the whole purpose of CMA was to act as the infra-structure
to provide buffers to 3D, camera, etc. in particular allowing sharing
of buffers between them. In other words, isn't CMA the memory manager?
If there's some deficiency with CMA for 3D graphics, it seems like
that should be raised with those designing CMA. Or, am I way off base
with my expectations of CMA?