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RPi4 KMS: console only displayed on HDMI1 when two displays are connected #4540

@HiassofT

Description

@HiassofT

When booting RPiOS lite on RPi4 with two 1920x1200 monitors connected the linux console is only displayed on HDMI1 if kms is used.

The monitor on HDMI0 receives a proper (1920x1200@60) signal, but the screen is blank.

Running "modetest" or switching VTs makes the console visible on HDMI0, too.

When booting with drm.debug=0x1f or drm.debug=0x14 the issue didn't show up, so it might be a timing issue or race. Testing without drm.debug or with drm.debug=0x04 reliably showed the issue across multiple reboots and cold boots.

System: RPiOS lite, 32bit running kernel 5.10.60 (commit 2dd846f, bcm2711_defconfig) and Aug 19 firmware

root@raspberrypi:~# uname -a
Linux raspberrypi 5.10.60-v7l+ #1 SMP Sun Aug 22 11:02:45 CEST 2021 armv7l GNU/Linux
root@raspberrypi:~# vcgencmd version
Aug 19 2021 12:27:01 
Copyright (c) 2012 Broadcom
version ef2c018dccdeb94b0376db62a2ea4c882f9b500d (clean) (release) (start)

dmesg with drm.debug=0x04: http://ix.io/3wEC

ping @mripard

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