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powerpc: Ensure that swiotlb buffer is allocated from low memory

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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
This commit is contained in:
Mike Rapoport 2019-12-04 14:35:24 +02:00 committed by Michael Ellerman
parent 656c21d6af
commit 8fabc62323
1 changed files with 8 additions and 0 deletions
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8
arch/powerpc/mm/mem.c
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@ -289,6 +289,14 @@ void __init mem_init(void)
BUILD_BUG_ON(MMU_PAGE_COUNT > 16);
#ifdef CONFIG_SWIOTLB
/*
* Some platforms (e.g. 85xx) limit DMA-able memory way below
* 4G. We force memblock to bottom-up mode to ensure that the
* memory allocated in swiotlb_init() is DMA-able.
* As it's the last memblock allocation, no need to reset it
* back to to-down.
*/
memblock_set_bottom_up(true);
swiotlb_init(0);
#endif