[PATCH 5.4 072/165] powerpc: Ensure that swiotlb buffer is allocated from low memory

Greg Kroah-Hartman
2020-01-11T10:26:57Z

From: Mike Rapoport <rppt@linux.ibm.com>

[ 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>
---
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 d30a2e6e68b4..9f5b32163bda 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -282,6 +282,14 @@ 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