Monitor on HDMI does not detect HDMI signal after disconnect/reconnect
by jhg6308 from LinuxQuestions.org on (#6GVWX)
I have the following setup:
Zotac CI323 mini-PC---USB/HDMI--> 2-port KVM --> Keyboard/Monitor
The OS is CentOS7 (yes, I know that's ancient; I plan to upgrade to Debian 12 "soon" :-)
The system is running WITHOUT X, i.e. the console is text only.
If I leave the monitor connected to the PC, it remains on indefinitely.
After I switch away to the other box on the KVM, OR power down the monitor without switching away, then later when I switch back or power on the monitor, the monitor does not detect the PC and goes into sleep mode.
It appears the PC has decided the monitor no longer exists and stops providing an HDMI signal.
The keyboard still works, and I can login "blind" and issue commands, but the monitor never detects a signal. I can login via SSH from a different system with no issues; the Zotac is fully operational, the only issue being that it appears to have stopped providing a signal on HDMI.
So far the only solution I've found is to reboot the system.
Some troubleshooting output:
Code:[jhg@janus ~]$ sudo lshw -c video
*-display
description: VGA compatible controller
product: Atom/Celeron/Pentium Processor x5-E8000/J3xxx/N3xxx Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
logical name: /dev/fb0
version: 21
width: 64 bits
clock: 33MHz
capabilities: pm msi vga_controller bus_master cap_list fb
configuration: depth=32 driver=i915 latency=0 resolution=1920,1080
resources: irq:123 memory:80000000-80ffffff memory:90000000-9fffffff
[jhg@janus ~]$ sudo lspci -k -s 00:02.0
00:02.0 VGA compatible controller: Intel Corporation Atom/Celeron/Pentium Processor x5-E8000/J3xxx/N3xxx Integrated Graphics Controller (rev 21)
DeviceName: Onboard IGD
Subsystem: ZOTAC International (MCO) Ltd. Device b301
Kernel driver in use: i915
Kernel modules: i915
ioport:f000(size=64) memory:c0000-dffffAlso, trying alternate consoles (Alt+Ctrl+F{2,3,4}) caused the system to start agetty on tty{2,3,4} but did not wake up the monitor.
Other things I've tried, with no luck:
- killing the logged in bash process. System relaunches agetty on tty1 but monitor remains off
- killing agetty on tty1; system relaunches agetty (as expected)
- while logged in, echoing text redirected to /dev/tty1, /dev/fb0, /dev/console - no effect
Immediate question: Is there a way to reset the HDMI device without having to reboot?
Other than that, I'd like to understand what's happening. The other device on the KVM is an Intel NUC11 mini-PC, Debian 12, runlevel 3, which does not have this issue.
Zotac CI323 mini-PC---USB/HDMI--> 2-port KVM --> Keyboard/Monitor
The OS is CentOS7 (yes, I know that's ancient; I plan to upgrade to Debian 12 "soon" :-)
The system is running WITHOUT X, i.e. the console is text only.
If I leave the monitor connected to the PC, it remains on indefinitely.
After I switch away to the other box on the KVM, OR power down the monitor without switching away, then later when I switch back or power on the monitor, the monitor does not detect the PC and goes into sleep mode.
It appears the PC has decided the monitor no longer exists and stops providing an HDMI signal.
The keyboard still works, and I can login "blind" and issue commands, but the monitor never detects a signal. I can login via SSH from a different system with no issues; the Zotac is fully operational, the only issue being that it appears to have stopped providing a signal on HDMI.
So far the only solution I've found is to reboot the system.
Some troubleshooting output:
Code:[jhg@janus ~]$ sudo lshw -c video
*-display
description: VGA compatible controller
product: Atom/Celeron/Pentium Processor x5-E8000/J3xxx/N3xxx Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
logical name: /dev/fb0
version: 21
width: 64 bits
clock: 33MHz
capabilities: pm msi vga_controller bus_master cap_list fb
configuration: depth=32 driver=i915 latency=0 resolution=1920,1080
resources: irq:123 memory:80000000-80ffffff memory:90000000-9fffffff
[jhg@janus ~]$ sudo lspci -k -s 00:02.0
00:02.0 VGA compatible controller: Intel Corporation Atom/Celeron/Pentium Processor x5-E8000/J3xxx/N3xxx Integrated Graphics Controller (rev 21)
DeviceName: Onboard IGD
Subsystem: ZOTAC International (MCO) Ltd. Device b301
Kernel driver in use: i915
Kernel modules: i915
ioport:f000(size=64) memory:c0000-dffffAlso, trying alternate consoles (Alt+Ctrl+F{2,3,4}) caused the system to start agetty on tty{2,3,4} but did not wake up the monitor.
Other things I've tried, with no luck:
- killing the logged in bash process. System relaunches agetty on tty1 but monitor remains off
- killing agetty on tty1; system relaunches agetty (as expected)
- while logged in, echoing text redirected to /dev/tty1, /dev/fb0, /dev/console - no effect
Immediate question: Is there a way to reset the HDMI device without having to reboot?
Other than that, I'd like to understand what's happening. The other device on the KVM is an Intel NUC11 mini-PC, Debian 12, runlevel 3, which does not have this issue.