[PATCH 02/12] drm/etnaviv: add devicetree bindings

[Russell King - ARM Linux]

On Sat, Dec 05, 2015 at 11:12:08AM +0100, Daniel Vetter wrote:
> Given that I think the current etnaviv is a sound architecture. And I'm
> not saying that because drm requires everything to be smashed into one
> driver, since that's simple not the case.

There's other reasons as well, mostly from the performance point of view.
Having separate DRM devices for each GPU means you need to use dmabuf to
share buffers across the GPUs.  This brings with it several kinds of
overhead:

1. having more fd usage in the client programs.
2. having more memory usage as a result.
3. having more locks, due to more object lists.
4. having the overhead from the DMA API when importing buffers between
   different GPU nodes.

>From my performance measurements over the last month, the top hit is
currently from the DMA API, so having to export and import buffers
between different GPU devices is just going to make that worse.

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