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* [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory
@ 2019-12-04 12:35 Mike Rapoport
  2019-12-04 12:35 ` Mike Rapoport
                   ` (3 more replies)
  0 siblings, 4 replies; 10+ messages in thread
From: Mike Rapoport @ 2019-12-04 12:35 UTC (permalink / raw)
  To: linux-kernel
  Cc: linuxppc-dev, linux-arch, linux-mm, iommu, Mike Rapoport,
	Christian Zigotzky, Benjamin Herrenschmidt, Christoph Hellwig,
	Darren Stevens, mad skateman, Michael Ellerman,
	Nicolas Saenz Julienne, Paul Mackerras, Robin Murphy,
	Rob Herring

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

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.

Link: https://lkml.kernel.org/r/F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de
Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Darren Stevens <darren@stevens-zone.net>
Cc: mad skateman <madskateman@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Rob Herring <robh+dt@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 be941d382c8d..14c2c53e3f9e 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -260,6 +260,14 @@ 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
 
-- 
2.24.0

^ permalink raw reply related	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2019-12-18  4:05 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-04 12:35 [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory Mike Rapoport
2019-12-04 12:35 ` Mike Rapoport
     [not found] ` <20191204123524.22919-1-rppt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2019-12-04 13:56   ` Christoph Hellwig
2019-12-04 13:56     ` Christoph Hellwig
2019-12-09  5:43 ` Michael Ellerman
2019-12-09  5:43   ` Michael Ellerman
2019-12-09  7:54   ` Mike Rapoport
2019-12-09  7:54     ` Mike Rapoport
2019-12-18  4:05 ` Michael Ellerman
2019-12-18  4:05   ` Michael Ellerman

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