I had to touch s390 again after a long break. Guess what I found. Marcelo 2.4.20 does not compile due to a syntax error in the chandev. And nobody posted anything. The stupid mainframe simply has no community. Nobody ever tests whatever is in the open. IBM produces "drops", which vendors incorporate in big chunks. The result is the proprietary software development model which happens to produce GPLed code.
Today I managed to do a little sparc work, applied Eric Brower's patch to support nodes with "interrupts" property, but without "intr" property. Also did other small things around serial ports, etc.