[PATCH] ARM: sunxi_defconfig: Enable CMA

[Maxime Ripard]

Hi,

On Sat, Jan 20, 2018 at 11:37:28AM +0800, Chen-Yu Tsai wrote:
> On Fri, Jan 19, 2018 at 9:32 PM, Maxime Ripard
> <maxime.ripard at free-electrons.com> wrote:
> > The DRM driver most notably, but also out of tree drivers (for now) like
> > the VPU or GPU drivers, are quite big consumers of large, contiguous memory
> > buffers. However, the sunxi_defconfig doesn't enable CMA in order to
> > mitigate that, which makes them almost unusable.
> >
> > Enable it to make sure it somewhat works.
> 
> IIRC the default size for CMA pretty much limits it to small tablet
> screen resolutions. Is this something we want to leave up to the
> user?

That's one of the pain points of CMA in our case. The amount of memory
you need depends on the resolution itself, but also the number of
multiple buffers you want to use, and even the number of planes you
want to use.

And then, you have to trade that off with the amount of RAM you have
on your board in order to still have something that's usable.

tl;dr: I don't really see how to define a value good enough for
everyone.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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