quoted

A hard(ware) lockup, not software.
That's why Intel says ICH5 doesn't do hotplug.

OIC.  I don't think there's much left to do from the driver side then.
Or is there any workaround?

I'm not familiar with the ICH5 SATA side but on the PATA side we also
need to run code to fix up chips on a hotplug (and *before* the plug in
some cases) - eg the ICH2 requires we turn off IORDY.