That patch reminds me about a nouveau bug[1] I had a couple of weeks ago. According to one of the developers behind nouveau it was caused by a new memory mapping/allocation scheme that broke things on systems with more than 4 GBs of RAM. Some device memory (registers etc) was mapped above 4 GBs and some of them don't like this. So he built a new kernel which reverted the change and the problem was "miraculously" fixed.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=689825