This is a note to let you know that I've just added the patch titled
powerpc: Ensure that swiotlb buffer is allocated from low memory
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-ensure-that-swiotlb-buffer-is-allocated-from.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c5db76c8b989866e636c89c3d2e91e47141fe875
Author: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Date: Wed Dec 4 14:35:24 2019 +0200
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@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>
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
