modesetting DDX puts display in unsupported configuration (asleep/blank) when native mode is higher than connection supports
To reproduce:
1-Connect ATI HD 3470 1002:95c0 or NVidia GT218 10de:0a65 via HDMI cable to 2560x1440 display
2-start the server
Actual behavior:
1-server on vtty7 produces "no signal" on otherwise black display screen
2-framebuffer vttys run in supported 1920x1080 mode
Expected behavior:
1-server runs in supported 1920x1080 mode
2-framebuffer vttys run in supported 1920x1080 mode
"Bisected" Regression Timeline:
OS/Kernel State /boot/vmlinuz timestamp
openSUSE 15.1/kernel 4.12.14 OK 2019-12-06
Fedora 31/5.3.16 kernel OK 2019-12-13
openSUSE 15.2/5.3.16 kernel OK 2019-12-31
Tumbleweed/5.4.7 kernel OK 2020-01-08
Mageia 7/5.4.10 kernel OK 2020-01-09
Mageia 8/5.4.11 kernel OK 2020-01-13
Debian Buster/kernel 4.19.x OK 2020-01-26
Tumbleweed/kernel 5.4.14 bad 2020-02-02
Fedora 31/5.4.20 kernel OK 2020-02-17
Fedora 30/5.4.21 kernel OK 2020-02-19
Fedora 31/5.5.5 kernel bad 2020-02-19
openSUSE 15.2/kernel 5.3.18 bad 2020-02-21
Behavior is normal when connected to 1920x1200 display or using dual-link DVI connection to 2560x1440 display.