On Fri, Dec 09, 2016 at 10:44:16PM +1100, Benjamin Herrenschmidt wrote:

On Fri, 2016-12-09 at 09:34 +0100, Daniel Vetter wrote:

quoted

Yeah if you have discrete vram then your dumb display driver isn't all
that pretty. We essentially just have the few drivers Dave hacked up to be
able to boot some servers. And there's definitely lots of room for more
shared code for those, and also some better infrastructure and helpers to
share more cod and make them better.

The massive pile of dumb framebuffers we all merged over the past 2 years
all use system/dma memory for scanout, and for those we have the very nice
cma helpers that take care of everything for you. 

Do they work if the system/DMA memory has to be physically contiguous
and at a fixed address ? The AST "ARM side" GPU is like that.

Yeah, if you wire up the dma_alloc_coherent to cma you'll get a contiguous
buffer pinned into place.

quoted

So it is possible, only reason vram dumb buffers look worse is that there's
only 3 and no one cares about them, vs about 20 and a very active community
of contributors (also for core drm improvements) for the other case.

Well, we could move offb to drm while at it I suppose that would be another
one (offb is the "dumb driver based on pre-programmed output by firmware).

One of the still in-flight drm drivers is the simpledrm thing meant for
all kinds of firmware drivers like efifb and similar things on arm for
pre-programmed output set up by firmware. I.e. no modeset support and
otherwise a lot of fake to make it work as drm driver, but the idea that
it's good enough until your real drm driver takes over.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch