[Mesa-dev] [Nouveau] [RFC] tegra: Initial support

Alexandre Courbot gnurou at gmail.com
Fri Nov 28 00:52:26 PST 2014

On Fri, Nov 28, 2014 at 5:48 PM, Thierry Reding
<thierry.reding at gmail.com> wrote:
> On Fri, Nov 28, 2014 at 02:14:24PM +0900, Alexandre Courbot wrote:
>> On 11/28/2014 01:39 AM, Thierry Reding wrote:
>> >Tegra K1 and later use a GPU that can be driven by the Nouveau driver.
>> >But the GPU is a pure render node and has no display engine, hence the
>> >scanout needs to happen on the Tegra display hardware. The GPU and the
>> >display engine each have a separate DRM device node exposed by the
>> >kernel.
>> >
>> >To make the setup appear as a single device, this driver instantiates
>> >a Nouveau screen with each instance of a Tegra screen and forwards GPU
>> >requests to the Nouveau screen. For purposes of scanout it will import
>> >buffers created on the GPU into the display driver. Handles that
>> >userspace requests are those of the display driver so that they can be
>> >used to create framebuffers.
>> >
>> >This has been tested with some GBM test programs, as well as kmscube and
>> >weston. All of those run without modifications, but I'm sure there is a
>> >lot that can be improved.
>> Tested with kmscube and Weston and I can confirm this works. However, EGL
>> clients inside Weston have their window filled with garbage (they seem to
>> run fine otherwise). Do you also experience this?
> To be honest, that wasn't part of my set of test cases. I had assumed
> that since Weston could composite buffers into a final scan out buffer
> everything else would just work as well. Do you have any particular
> demos that aren't working?

Anything using EGL under Wayland - the simplest case would be
weston-simple-egl. glmark2 also displays a broken window, but then
crashes shortly after. With weston-simpe-egl I get the framerate
feedback and can see the GPU performance counters moving as expected,
indicating that the app is rendering correctly but that Weston gets
the wrong buffer to display.

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