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f8839289
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2020-12-15T12:22:48
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Potential fix for bug 5393 - KMSDRM: using atomic mode setting breaks GPU compatibility
Substring
I was trying the KMSDRM video backend with some very simple programs that were working ok on 2.0.12. The same code won?t work on the current dev branch and I get:
DEBUG: check_modesetting: probing ?/dev/dri/card0?
DEBUG: /dev/dri/card0 connector, encoder and CRTC counts are: 4 5 6
DEBUG: check_modesetting: probing ?/dev/dri/card0?
DEBUG: /dev/dri/card0 connector, encoder and CRTC counts are: 4 5 6
DEBUG: KMSDRM_VideoInit()
DEBUG: Opening device /dev/dri/card0
DEBUG: Opened DRM FD (3)
DEBUG: no atomic modesetting support.
DEBUG: Video subsystem has not been initialized
INFO: Using SDL video driver: (null)
DEBUG: Video subsystem has not been initialized
After carefully checking, the radeon driver doesn?t support atomic modesetting. That?s not the only problem : the same happens with the amdgpu driver if we disable Display Core (kernel parameter amdgpu.dc=0, which is required to get analogue outputs working).
This is a major regression in the KMSDRM driver.
Using atomic mode setting is great, but having no fallback to the "standard KMS" is bad.
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