I observe exactly the same behavior with my Fritzbox 3490, both with the stable and the snapshot release.
Maybe our boxes have a different USB controller ?
Once you've done that there's a xhcifw.mem file sitting in there, perhaps you can rename this file and it's the one ? I notice this file is the exact same size as the one linked to above though.
Now I have the same file from three sources (github, AVM image and renesas). I renamed the files to renesas_usb_fw.mem and copied them to /lib/firmware.
Anyhow, I get still the same messages:
root@3490-DG:~# logread | grep usb
Mon Feb 24 08:39:41 2025 kern.info kernel: [ 0.359079] usbcore: registered new interface driver usbfs
Mon Feb 24 08:39:41 2025 kern.info kernel: [ 0.364637] usbcore: registered new interface driver hub
Mon Feb 24 08:39:41 2025 kern.info kernel: [ 0.369936] usbcore: registered new device driver usb
Mon Feb 24 08:39:41 2025 kern.info kernel: [ 9.183500] pci 0000:01:00.0: quirk_usb_early_handoff+0x0/0x9d4 took 5656357 usecs
Mon Feb 24 08:40:15 2025 kern.err kernel: [ 74.749475] xhci_hcd 0000:01:00.0: failed to load firmware renesas_usb_fw.mem: -145
root@3490-DG:~# logread | grep xhci
Mon Feb 24 08:40:15 2025 kern.err kernel: [ 74.749475] xhci_hcd 0000:01:00.0: failed to load firmware renesas_usb_fw.mem: -145
Mon Feb 24 08:40:15 2025 kern.warn kernel: [ 74.755786] xhci_hcd: probe of 0000:01:00.0 failed with error -145
Don't worry about it, the other file is OK it's just that it's not getting loaded early enough. You need to build openwrt yourself and make those changes with loading the file earlier.
I build openwrt as you described and error messages disappeared.
But the ls doesn't show attached devices as expected.
root@3490-DG:~# lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux 6.6.73 xhci-hcd xHCI Host Controller
Bus 001 Device 002: ID 048d:1167 USB007 USB Mass Storage Device
Bus 002 Device 001: ID 1d6b:0003 Linux 6.6.73 xhci-hcd xHCI Host Controller
root@3490-DG:~# ls -al /dev/sd*
ls: /dev/sd*: No such file or directory
root@3490-DG:~# dmesg | grep usb
[ 0.365881] usbcore: registered new interface driver usbfs
[ 0.371415] usbcore: registered new interface driver hub
[ 0.376800] usbcore: registered new device driver usb
[ 9.136148] pci 0000:01:00.0: quirk_usb_early_handoff+0x0/0x9a4 took 5652917 usecs
[ 11.753335] usb usb2: We don't know the algorithms for LPM for this host, disabling LPM.
[ 12.280497] usb 1-1: new high-speed USB device number 2 using xhci_hcd
root@3490-DG:~# dmesg | grep xhc
[ 11.699195] xhci_hcd 0000:01:00.0: xHCI Host Controller
[ 11.703084] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus number 1
[ 11.715983] xhci_hcd 0000:01:00.0: hcc params 0x014051cf hci version 0x100 quirks 0x0000001100000090
[ 11.724530] xhci_hcd 0000:01:00.0: xHCI Host Controller
[ 11.729014] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus number 2
[ 11.736413] xhci_hcd 0000:01:00.0: Host supports USB 3.0 SuperSpeed
[ 12.280497] usb 1-1: new high-speed USB device number 2 using xhci_hcd