4c421a34f8
Instead of initializing UDMA mode, we turned it off and made sure that it stays off by turning on the "UDMA enable by SET FEATURES" disable. The damage was limited by bugs in cookie lookup, and suitable initialization by some BIOSes. The cookie list has slaves before masters, and the unit number is ignored when cookies are looked up, so cookie lookup always finds cookies for slaves and the bug only clobbers slaves, so the bug was harmless for common configurations with no slaves or only non-UDMA slaves. UDMA initialization for masters actually worked if the BIOS turns on the UDMA mode bit and turns off the "UDMA enable by SET FEATURES" disable.