On Fri, Jan 18, 2019 at 01:46:46PM +0100, Christian Zigotzky wrote:

Sorry, it's not possible to patch 
'257002094bc5935dd63207a380d9698ab81f0775' with your patch. I also tried it 
manually but without any success.

Weird:

hch@carbon:~/work/linux$ git checkout 257002094bc5935dd63207a380d9698ab81f0775
HEAD is now at 257002094bc5 powerpc/dma: use the dma-direct allocator for coherent platforms
hch@carbon:~/work/linux$ patch -p1 < dbg.diff 
patching file kernel/dma/direct.c

I've pushed the result to

git://git.infradead.org/users/hch/misc.git

as a new powerpc-dma.6-debug branch