From: Mike Rapoport <rppt@xxxxxxxxxxxxx> [ 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@xxxxxxxxxxx> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20191204123524.22919-1-rppt@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/powerpc/mm/mem.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 1efe5ca5c3bc..5bb2c89d55c8 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -330,6 +330,14 @@ 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 -- 2.20.1
