OK, I'm just giving a short update on what I've found. In asm-mips/mach-generic/ide.h is a function ide_probe_legacy() which is called to determine IDE support but which returns 0 for my setup. I simply hard-wired this value to 1 and now at least it tries to probe something.
However, it is looking at ioports in the range 366-3f6, which are already reserved by something else. Anyway, that is rather a legacy PC-style layout and thus probably doesn't apply to the PCMCIA version, if I'm not mistaken. I also tried simply removing the check whether they are reserved, but that just OOPSed.
Looking at EBOOT (a bootloader for win CE that boots off the compactflash), it tries to access the IDE interface at address 0x1a00000 for io_addr and 0x1a00000e for control, let's see if I can find any IDE hardware at that address...
Uhm, I don't think you'll resolve this that easily. There is some code that needs to go in the au1x00 socket driver which means you would have to understand pretty well how this thing works. Ultimately the addresses you'll probe are very high ioremapped addresses, since the pcmcia attribute, common mem, and i/o are 36 bit physical addresses.
Pete
