Visual DRM plane artifacts on vertical edges.

Start with the DRM plane configuration in /sys/kernel/debug/dri/1/state on a Raspberry Pi 5, using the reported three-video, two-display layout and the supplied plane positions. Confirm the vertical-edge artifacts and narrow down which plane or layout condition triggers them; done means the behavior is reproducible and the kernel issue has a verified fix.

Describe the bug

While playing around in my software, I managed to come across a DRM plane layout that results in artifacts on vertical plane edges. Look at this screenshot:

I'm playing three videos across two displays (separated by the white line in the screenshot). As a result my software splits the middle video into two planes (labeled '2' and '3'). To reduce overdraw, my software also removes the non-visible part of the plane '3' that's hidden behind the plane '4'.

The video is 560x360 pixel, DRM "YU12". The relevant output in /sys/kernel/debug/dri/1/state for plane '3' is:

    crtc-pos=360x848+0+124
    src-pos=65.000000x320.000000+280.000000+0.000000

For plane '4':

    crtc-pos=1560x1080+360+0
    src-pos=560.000000x320.000000+0.000000+0.000000

So plane '4' touches plane '3' at x=360. That edge has odd bleeding of pixels going on:

Steps to reproduce the behaviour

Not sure yet. That specific configuration doesn't work. Resizing the middle video (and thus plane '2' and '3') likely fixes the issue. Tested only on a Pi5 for now.

Device (s)

Raspberry Pi 5

System

My custom info-beamer OS. Using 6.6.33 kernel from https://github.com/raspberrypi/rpi-firmware:

Linux info-beamer-xxxxxxxxx 6.6.33-v8+ #1770 SMP PREEMPT Wed Jun 12 17:47:55 BST 2024 aarch64 GNU/Linux                                                                                                                                                                                                                                                                                                                                  
2024/06/05 16:41:49 
Copyright (c) 2012 Broadcom
version 6fe0b091 (release) (embedded)

Logs

No response

Additional context

No response