weston rdp black screen

[Maciej Pijanowski]

On 10.09.2020 16:32, Maciej Pijanowski wrote:
>
> Hello,
>
> I'm having exactly the same issue as described in the [1].
> I have a custom Yocto build running on the embedded board
> with Mali GPU. Mali GPU was also used in the mentioned thread.
> So maybe there is something in common.
>
> When RDP backend is used as a main backend
> (in the core section) I can see the screen content in the RDP client.
> When the core backend is DRM and the RDP is started via the screen-share
> plugin, I can only see the black screen in the RDP client (although
> the input works
> correctly).
>
> I tried running the same combination on Fedora VM or on the RPi4
> and in those cases the screen-share works correctly with RDP.
>
> I've been looking for some differences in the logs between those setups.
> I have noticed the EGL config in case of Mali to be different than in case
> of the other ones.
>
> Mali:
>
> [07:24:23.919] Bad/unknown DRM format code 0x00000000.
> [07:24:23.919] Unable to use first choice EGL config with XRGB8888,
> succeeded with alternate ARGB8888.
> ...
> [07:24:23.923] GL version: OpenGL ES 2.0 "fa33ed7"
> [07:24:23.923] GLSL version: OpenGL ES GLSL ES 1.00
> [07:24:23.923] GL vendor: ARM
> [07:24:23.923] GL renderer: Mali-400 MP
> ...
> [07:24:24.006] Chosen EGL config details: id: 9 rgba: 8 8 8 8 buf: 32
> dep: 24 stcl: 8 int: 0-10 type: win|pix|pbf|swap_preserved vis_id:
> ARGB8888
> (0x34325241)
>
> RPi:
>
> [07:04:41.917] GL version: OpenGL ES 3.1 Mesa 20.0.2
> [07:04:41.917] GLSL version: OpenGL ES GLSL ES 3.10
> [07:04:41.917] GL vendor: Broadcom
> [07:04:41.917] GL renderer: V3D 4.2
> ...
> [07:04:42.032] Chosen EGL config details: id: 17 rgba: 8 8 8 0 buf: 24
> dep: 0 stcl: 0 int: 1-1 type: win vis_id: XRGB8888 (0x34325258)
>
>
> I've changed the format on the RPi ARGB8888 and it still works fine.
>
So I've been investigating this issue further. I've checked for the
pixeldata
here [2]
and in the cases with the black screen there was nothing dumped.

I have traced it further back to the glReadPixels call [3]. Once I switched
the pixel format to the PIXMAN_a8b8g8r8 (gl_format to GL_RGBA) it started
to work correctly. Both VNC [4] and RDP backends now work fine with the
screen-share on platform with Mali GPU and libMali blob.

As I got this working, I could just patch the code to use the given
pixel format.
But I would prefer to fix things upstream. Any hints on what would be
"the proper"
way of fixing this issue are welcome.

I also added Stefan Agner to CC as he was changing this part of the code
lately in screen-share and we were discussing this matter in [5]. I hope
this is fine.

Thanks,

[2]
https://gitlab.freedesktop.org/wayland/weston/-/blob/master/compositor/screen-share.c#L888
[3]
https://github.com/3mdeb/weston/blob/use_GL_RGBA/libweston/renderer-gl/gl-renderer.c#L1551
[4] https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/36
[5]
https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/362#note_623870

>
> One more observation - if I forced the DRM backend to use the pixman
> renderer
> (by adding the use-pixman=true in the weston.ini), the cloned content
> appeared
> correctly in the RDP client. Of course the performance and usability
> dropped,
> as the GPU was no longer used for rendering.
> It clearly suggests that the problem is somewhere around the Mali library.
>
> Any suggestions how to approach further debugging of these kind of issues
> are highly appreciated.
>
> Thank you
>
> [1]
> https://lists.freedesktop.org/archives/wayland-devel/2019-April/040382.html
>
> -- 
> Maciej Pijanowski
> Embedded Systems Engineer
> GPG: 9963C36AAC3B2B46
> https://3mdeb.com | @3mdeb_com
>
> _______________________________________________
> wayland-devel mailing list
> wayland-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/wayland-devel

-- 
Maciej Pijanowski
Embedded Systems Engineer
GPG: 9963C36AAC3B2B46
https://3mdeb.com | @3mdeb_com

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