Commit 055b4a62 authored Dec 04, 2019 by Mike Rapoport Committed by Greg Kroah-Hartman Jan 12, 2020

powerpc: Ensure that swiotlb buffer is allocated from low memory



[ Upstream commit 8fabc623238e68b3ac63c0dd1657bf86c1fa33af ]

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: Sasha Levin <sashal@kernel.org>

parent 7d5ad9fe

arch/powerpc/mm/mem.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -344,6 +344,14 @@ 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