On Mon, Jan 22, 2018 at 3:34 PM, Maxime Ripard maxime.ripard@free-electrons.com wrote:

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@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.

Yeah, that's what I thought. On the other hand, I don't think any of the kernelci boards have display enabled? So either way we won't see any automated tests fail.

ChenYu