[PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory

[Christoph Hellwig]

On Wed, Dec 04, 2019 at 02:35:24PM +0200, Mike Rapoport wrote:
> From: Mike Rapoport <rppt at linux.ibm.com>
> 
> Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a
> system has more physical memory than this limit, the swiotlb buffer is not
> addressable because it is allocated from memblock using top-down mode.
> 
> Force memblock to bottom-up mode before calling swiotlb_init() to ensure
> that the swiotlb buffer is DMA-able.
> 
> Link: https://lkml.kernel.org/r/F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de
> Reported-by: Christian Zigotzky <chzigotzky at xenosoft.de>
> Signed-off-by: Mike Rapoport <rppt at linux.ibm.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch at lst.de>