powerpc: Ensure that swiotlb buffer is allocated from low memory
commit 8fabc623 upstream. 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. Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20191204123524.22919-1-rppt@kernel.org Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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