hotplug vga(drm radeon) turns disconnected to connected, but is still disabled from sys

Here is my graphic card:

03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos [Radeon HD 6450/7450/8450 / R5 230 OEM]        Subsystem: XFX Pine Group Inc. Caicos [Radeon HD 6450/7450/8450 / R5 230 OEM]        Kernel driver in use: radeon

After booting without Vga plugging in, I hotplug Vga monitor. But the screen is still black and lightdm/xdm doesn't show up. I noticed though

• VGA status is connected,
• butenabled is disabled:

root@lccy7:~# cat /sys/class/drm/card0-VGA-1/status connectedroot@lccy7:~# cat /sys/class/drm/card0-VGA-1/enabled disabled

xdm runs happily in the background:

root@lccy7:~# systemctl status xdm* xdm.service - X-Window Display Manager   Loaded: loaded (/lib/systemd/system/xdm.service; enabled; vendor preset: enabled)   Active: active (running) since Tue 2020-05-12 14:37:03 CST; 1h 3min ago Main PID: 2589 (xdm)    Tasks: 4 (limit: 4915)   CGroup: /system.slice/xdm.service           |-2589 /usr/bin/xdm -nodaemon           `-2604 /usr/lib/xorg/Xorg :0 -auth /var/lib/xdm/authdir/authfiles/A:0-InChxFMay 12 14:37:01 lccy7 systemd[1]: Starting X-Window Display Manager...May 12 14:37:03 lccy7 systemd[1]: Started X-Window Display Manager.May 12 14:37:04 lccy7 xdm[2635]: pam_unix(greeter:session): session opened for user root by (uid=0)

Once I switch to other tty(e.g., Ctrl Alt F1, it is both connected and enabled:

root@lccy7:~# cat /sys/class/drm/card0-VGA-1/status connectedroot@lccy7:~# cat /sys/class/drm/card0-VGA-1/enabled enabled

I turned drm to verbose mode with drm.debug=0x1e log_buf_len=4M, and here is kernel log(journalctl -b 0 -k | grep -E "enabled|\bconnected|hotplug" | grep -v i2c):

# before plugging in Vga:root@lccy7:~# journalctl -b 0 -k | grep -E "enabled|\bconnected|hotplug" | grep -v i2cMay 12 16:34:31 lccy7 kernel: console [tty0] enabledMay 12 16:34:31 lccy7 kernel: raid6: .... xor() 1078 MB/s, rmw enabledMay 12 16:34:31 lccy7 kernel: [drm] radeon kernel modesetting enabled.May 12 16:34:31 lccy7 kernel: [drm] PCIE GART of 1024M enabled (table at 0x0000000000274000).May 12 16:34:31 lccy7 kernel: radeon 0000:03:00.0: WB enabledMay 12 16:34:31 lccy7 kernel: [drm:drm_sysfs_hotplug_event] generating hotplug eventMay 12 16:34:31 lccy7 kernel: [drm:drm_sysfs_hotplug_event] generating hotplug eventMay 12 16:34:31 lccy7 kernel: [drm:drm_sysfs_hotplug_event] generating hotplug eventMay 12 16:34:31 lccy7 kernel: radeon 0000:03:00.0: No connectors reported connected with modesMay 12 16:34:31 lccy7 kernel: [drm:drm_enable_connectors] connector 37 enabled? noMay 12 16:34:31 lccy7 kernel: [drm:drm_enable_connectors] connector 39 enabled? noMay 12 16:34:31 lccy7 kernel: [drm:drm_enable_connectors] connector 41 enabled? noMay 12 16:34:31 lccy7 kernel: [drm] amdgpu kernel modesetting enabled.May 12 16:34:31 lccy7 kernel: sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUAMay 12 16:34:31 lccy7 kernel: sd 2:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUAMay 12 16:34:36 lccy7 kernel: [drm:drm_sysfs_hotplug_event] generating hotplug eventMay 12 16:34:36 lccy7 kernel: [drm:drm_fb_helper_hotplug_event] May 12 16:34:36 lccy7 kernel: [drm:drm_enable_connectors] connector 37 enabled? noMay 12 16:34:36 lccy7 kernel: [drm:drm_enable_connectors] connector 39 enabled? noMay 12 16:34:36 lccy7 kernel: [drm:drm_enable_connectors] connector 41 enabled? no# After plugging to Vga: May 12 16:41:35 lccy7 kernel: [drm:radeon_atombios_connected_scratch_regs] CRT1 connectedMay 12 16:41:35 lccy7 kernel: [drm:output_poll_execute] [CONNECTOR:41:VGA-1] status updated from disconnected to connectedMay 12 16:41:35 lccy7 kernel: [drm:drm_sysfs_hotplug_event] generating hotplug eventMay 12 16:41:35 lccy7 kernel: [drm:radeon_atombios_connected_scratch_regs] CRT1 connected# After switching to tty1: May 12 16:45:39 lccy7 kernel: [drm:drm_fb_helper_hotplug_event] May 12 16:45:39 lccy7 kernel: [drm:radeon_atombios_connected_scratch_regs] CRT1 connectedMay 12 16:45:39 lccy7 kernel: [drm:drm_enable_connectors] connector 37 enabled? noMay 12 16:45:39 lccy7 kernel: [drm:drm_enable_connectors] connector 39 enabled? noMay 12 16:45:39 lccy7 kernel: [drm:drm_enable_connectors] connector 41 enabled? yes

Here is the full drm|radeon log(with many ioctl logs): https://paste.ubuntu.com/p/rWDZ7GCdN6/

From the full log, I found the first ioctl after switching to tty is:

May 12 16:44:41 lccy7 kernel: [drm:drm_ioctl] pid=4206, dev=0xe200, auth=1, DRM_IOCTL_MODE_SETCRTC

I have made sure if I boot with plugged Vga, lightdm/xdm can show without problems.