Lich
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When will the Full KMS driver for Raspberry Pi 4 be available?

Mon Oct 07, 2019 10:11 pm

As far as I understand, drivers for GPU Videocore VI are not finalized yet. I ran into a problem that video display in OpenCV works worse than on Raspberry 3.

Can we expect the Full KMS driver to be released in the near future?

jamesh
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Re: When will the Full KMS driver for Raspberry Pi 4 be available?

Mon Oct 07, 2019 10:34 pm

No. We are currently concentrating on getting fkms fully sorted. However, that work will benefit Kms in the long run.
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6by9
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Re: When will the Full KMS driver for Raspberry Pi 4 be available?

Tue Oct 08, 2019 7:49 am

I have it working for dpi displays, and in theory dsi should just work too. I'll try to sort out a pr in the next few days.

Then again, AFAIK opencv has no direct input to kms, so any issue is likely to be egl related rather than kms. The difference between kms and fkms in rendering performance is minimal.
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Lich
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Re: When will the Full KMS driver for Raspberry Pi 4 be available?

Tue Oct 08, 2019 8:02 pm

jamesh, 6by9,

Thanks for the quick response!

Yes, according to my tests on Raspberry 3, OpenCV's display performance is approximately the same with Full KMS and Fake KMS. Displaying the same HD video using OpenCV imshow on Raspberry 3 loads the CPU by 32-38%, on Raspberry 4 - 35-50% (using the same image on the SD card). Maybe the problem is related to Qt5 - OpenCV is compiled with OpenGL and this GUI. In the next few days I will try to compile OpenCV with GTK.

I also tested various output methods in the VLC player - it seems that hardware acceleration only works with MMAL (full screen layer).

6by9
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Re: When will the Full KMS driver for Raspberry Pi 4 be available?

Tue Oct 08, 2019 9:02 pm

Pi0-3 and Pi4 have various significant differences in the 3D hardware, so I would expect some difference in CPU load. Generally I would have expected Pi4 to be better, but it depends on exactly the paths being taken.

DRM supports direct rendering of planes, but it also only supports a single authorised client at a time. If X is running, then it is the client, and other applications can't directly add layers.
With FKMS we can cheat and ask the firmware to add layers via either DIspmanX or MMAL. Generally composition is done by EGL which isn't as efficient, and depends on how the application drives it as to how efficient it is.
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rhildinger
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Re: When will the Full KMS driver for Raspberry Pi 4 be available?

Tue Oct 08, 2019 9:20 pm

How might one educate oneself on the whole KMS vs FKMS driver system?

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