Read the statement by Michael Teeuw here.
Applied change to config.txt, MM fails to boot.
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 Update to 2.4.0, and made the sudo nano /boot/config.txt dtoverlay=vc4-kms-v3d change. Shut down Pi, powered Pi back on, and now fails to boot, showing just a cursor top left of monitor. 
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 Comment out the dtoverlay=vc4-kms-v3d change, and Pi boots, MM starts OK. Does it matter where in config.txt that the new line is placed? 
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 Or…, is it best to use the sudo raspi-config /Advanced/… route? 
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 Did you remove these entries in the config.txt? display_rotate = 1 
 avoid_warnings = 1
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 display_rotate = 1 - is commented out (I’m happy with MM in landscape mode) 
 avoid_warnings = 1 - line doesn’t exist.
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 I had the same issue. I changed dtoverlay=vc4-kms-v3dtodtoverlay=vc4-fkms-v3dand was able to boot up again.
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 That doesn’t work for me, MM boots to a few lines about blocks, then nothing else. 
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 Did you try the rasps-config tool to configure the GL driver? 
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 No, because if that kills it, I don’t know how to bring it back - what file to edit etc…? 
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 @richard238 It just modifies the config.txt for you in a save way. There is a bigger chance of you killing your pi doing it manually than using the config tool. 


