aroman_ro
Posts: 23
Joined: Mon May 06, 2019 2:01 pm

Display rotation with vc4 kms

Fri Mar 13, 2020 3:11 pm

Is there any method of rotating the display at the vc4 kms level?

Something like we had for the firmware driver, with a rotation setting in config.txt?

I know it can be done by xorg, but that's done in xorg modesetting and that has a bug with vsync.
Here is a bug report: https://gitlab.freedesktop.org/xorg/xserver/issues/996

I would like to try rotating the display directly with the lower level kernel driver. Is that possible?

jamesh
Raspberry Pi Engineer & Forum Moderator
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Re: Display rotation with vc4 kms

Fri Mar 13, 2020 3:22 pm

When using FKMS you need to use the xrandr settings. The config.txt entries don't play nicely with FKMS
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aroman_ro
Posts: 23
Joined: Mon May 06, 2019 2:01 pm

Re: Display rotation with vc4 kms

Fri Mar 13, 2020 8:34 pm

Exactly what I was afraid of... I'm going to look over the sources to see if there is a relatively easy way before giving up, though.
Otherwise we have to go with wayland or we'll have to compile that dev branch that fixes (hopefully) the issue.

6by9
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Re: Display rotation with vc4 kms

Sat Mar 14, 2020 3:16 pm

If writing your own code then you do have the option of the writeback connector which wraps the transposer hardware block. AIUI Android's SurfaceFlinger is the main client that uses it currently. It's probably not something that can be integrated into Xorg easily though.
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aroman_ro
Posts: 23
Joined: Mon May 06, 2019 2:01 pm

Re: Display rotation with vc4 kms

Mon Mar 16, 2020 9:57 am

Unfortunately, we need to allow people using chrome and so on, not only our own application.

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