I also have C2600 v1.1 with OpenWrt 19.07
On my case system work stabile when scaling_governor set to performance but my router got three times reboot after seven days.
Reboot was always when I try download big ISO file and on the same time I tried copy some file on LAN.
My max uptime was 83 day and currently 39 days.
I think this settings don't have sense.
performance - always set CPU clock to max and on this point at 1200MHz
Setting scaling_min_freq got sense only when scaling_governor is set to ondemand.
I think bellow settings should also be set to policy1 directory (I got this on OpenWrt 19.07)
The routers are consuming more energy by not clocking down. However, I prefer it to keep running without reboots. The maximum possible speed is also not used, as that might also trigger stability issues. 1.2GHz seems stable to what I can observe.
The ondemand scheduler always caused issues sooner or later.
I only use scaling_governor, my devices are at 345, 166 and 87 (it was powered down, not a reboot) days.
Use them as APs though, so there might be a difference, the one with the longest uptime, uses 19.07.3, the other two 19.07.6.
Just bought a used C2600 v1.1 and I am on 21.02.1, don't see many posts about this version's behavior. Have everything on defaults ( scaling_min_freq at 600000, governor ondemand), let's see how it goes
Strange indeed, but who knows what is causing it. Let's please update each other if unplanned reboots occur. For the interim I added the hints in the Wiki as well for others that might have issues and are looking for ideas on how to navigate around the issue.