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From: Mike Rapoport <rppt@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org,
	Darren Stevens <darren@stevens-zone.net>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	Rob Herring <robh+dt@kernel.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	mad skateman <madskateman@gmail.com>,
	Christian Zigotzky <chzigotzky@xenosoft.de>,
	linuxppc-dev@lists.ozlabs.org, Christoph Hellwig <hch@lst.de>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory
Date: Wed,  4 Dec 2019 14:35:24 +0200
Message-ID: <20191204123524.22919-1-rppt@kernel.org> (raw)

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

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Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-04 12:35 Mike Rapoport [this message]
2019-12-04 13:56 ` Christoph Hellwig
2019-12-09  5:43 ` Michael Ellerman
2019-12-09  7:54   ` Mike Rapoport

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