No display output after upgrading to App 2.5.0 (image v1.4.0)

[OriAndDarkChocolate]

This seems to be similar to the issue #376 #376

After upgrading offline to App 2.5.0, no display output to the webgui anymore.

# cat /etc/kvm/hdmi_version
ux


[VI BE_Dbg_Info]
VIPreBEDoneSts          :0x0            VIPreBEDmaIdleStatus    :0x7
[VI Post_Dbg_Info]
VIIspTopStatus          :0x3ff
[VI DMA_Dbg_Info]
VIWdma0ErrStatus        :0x3000000      VIWdma0IdleStatus       :0xffffffff
VIWdma1ErrStatus        :0x3000000      VIWdma1IdleStatus       :0xffffffff
VIRdmaErrStatus         :0x3000000      VIRdmaIdleStatus        :0xffffffff
[VI ISP_PIPE_A FE_Dbg_Info]
VIPreFERawDbgSts        :0x3ff          VIPreFEDbgInfo          :0x3f
[VI ISP_PIPE_A]
VIOutImgWidth           :1920
VIOutImgHeight          :1080
VIInImgWidth            :1920
VIInImgHeight           :1080
VIDevFPS                :  60
VIFPS                   :   0
VISofCh0Cnt             : 740
VIPreFECh0Cnt           :   0
VIPreBECh0Cnt           :   0
VIPostCnt               :   0
VIDropCnt               :   0
VIDumpCnt               :   0
[VI ISP_PIPE_A Csi_Dbg_Info]
VICsiIntStatus0         :0x3
VICsiIntStatus1         :0x0
VICsiCh0Dbg             :0x0
VICsiCh1Dbg             :0x0
VICsiOverFlowCnt        :   0
VICsiCh0WidthGTCnt      :   0
VICsiCh0WidthLSCnt      :  32
VICsiCh0HeightGTCnt     :   0
VICsiCh0HeightLSCnt     :   0

After S95nanokvm restart, the terminal will output repeatedly:
[2026-08-08 18:21:18.544] [error] [kvm_vision.go:50] failed to read kvm image: -4
[2026-08-08 18:21:18.577] [error] [kvm_vision.go:50] failed to read kvm image: -4
[2026-08-08 18:21:18.611] [error] [kvm_vision.go:50] failed to read kvm image: -4

Setting the following in another ssh session does not help neither.
echo 1920 > /kvmapp/kvm/width; echo 1080 > /kvmapp/kvm/height

Downgrading the app version per the instruction on issue #376 and reboot, and everything is back to normal.
#376 (comment)

Thought to report my experience before it's available on the webgui.

[SiYue-ZO]

Thank you for reporting this issue.

I have tried to reproduce the problem, but everything works as expected in my environment. It would be helpful if you could provide more details about your setup and the exact steps that trigger the issue.

Once we have this information, we can take a closer look. Thanks for your help!

[OriAndDarkChocolate]

Typical setup, Dell (Broadwell) workstation, gpu HDMI port to the Cube (full version) HDMI port (powered by proper usb-c adapter), has been working reasonably well for months in previous App versions with some reboots in between.

After an offline update of App to 2.5.0 via the webgui (tar.gz from the github page and checksum verified) and rebooted, as noted in the post above, VIFPS showed 0. VIDevFPS seems normal at 60. No extra step is needed to reproduce this, just upgrade and reboot.

cat /kvmapp/version showed it was at 2.5.0, as did on the webgui showing the new version. So I would assume the upgrade was successful.

Setting HDMI auto or manual mode made no difference (e.g. echo 1 > /etc/kvm/hdmi_mode)
and tried, echo 1920 > /kvmapp/kvm/width; echo 1080 > /kvmapp/kvm/height
After S95nanokvm restart, as noted above, keep getting [error] [kvm_vision.go:50] failed to read kvm image: -4
Rebooted a few times with no impact, VIFPS showed 0.

Once App was downgraded back to 2.4.3 (per issue post $376) and rebooted, everything works again with no further changes. I'd avoid upgrading to 2.5.0 for now, I needed it for remote access for the next little while, so not sure what other info can be provided to pin point the cause. I'm ok for now but just to report a potential issue.

[watermeko]

1. Upgrade the image to 1.4.3, then upgrade the APP to 2.5.0. https://github.com/sipeed/NanoKVM/releases/tag/v1.4.3 (Try this first.)
2. Do you use HTTPS to access web pages?
3. Run /kvmapp/system/tool/nanokvm_update_edid /kvmapp/system/tool/E21_NanoKVM.bin to refresh the EDID, then restart NanoKVM.

[OriAndDarkChocolate]

Thanks for the suggestions. Using HTTPS to access the webgui. I'll try updating the image the next time going onsite, can't risk losing the access for now.

[watermeko]

Glad to hear that! Please re-open this issue when the problem occur again.