So I ran "pacman -Syu" on my Raspberry Pi, original B model. This install is quite old, it's been upgraded this way many times over the past few years. I had updated individual packages at times, but had not upgraded the kernel in a while. I came up from a 4.4.x release to the current release. Following the upgrades, I rebooted the Pi and it was unable to boot.
Initially, the Pi would not boot at all. When power is applied, the ACT light flashes just once and then nothing else happens. The screen stays dark.
I tried to manually rebuilt my /boot partition from the raspberrypi-firmware package in ALARM's repos but this resulted in no change at all. Also manually recopied the kernel and initrd from the arch package just to rule out corruption. No change.
I then grabbed a copy of Raspbian and extracted its /boot partition and copied everything other than "kernel.img", "cmdline.txt" and "config.txt" into my Pi's /boot partition, overwriting any existing files. After doing this, the Pi does boot and the display comes on, but the boot process stops midway through with no obvious error messages explaining the cause. The USB stack seems to have issues, because if I leave the system running, repeated messages like the last one in the below screenshot appear (the messages about device descriptor read errors). I cannot use any input devices and the Ethernet lights never come on.
Link to a screenshot of what I'm able to see: https://www.dropbox.com/s/nfu6cfmo8bm6xpa/2017-04-02%2018.22.03.jpg?dl=0
I'm wondering if somehow the repos for the ARMv6 processor somehow got "contaminated" with code from a later version of the Pi?
I do not have a copy of the older kernel package (to free up some space I had cleared the pacman cache) so I cannot roll back to my previous kernel (I can't find an archive of ALARM packages).
I know this is not a hardware problem as I tried the SD card in two other Pi's, another B and also a B+ first generation and had exactly the same result.
I'm hoping to be able to repair this installation, without having to redo the entire setup from scratch and reconfigure everything from the past few years.
Anyone have any advice?