From: Christoph Hellwig <hch@lst.de>
To: David Daney <ddaney@cavium.com>, Huacai Chen <chenhc@lemote.com>
Cc: "Hongliang Tao" <taohl@lemote.com>, "Hua Yan" <yanh@lemote.com>,
"Alex Smith" <alex.smith@imgtec.com>,
"Ralf Baechle" <ralf@linux-mips.org>,
"Rafał Miłecki" <zajec5@gmail.com>,
linux-mips@linux-mips.org
Subject: mb() calls in octeon / loongson swiotlb dma_map_ops
Date: Sat, 30 Dec 2017 17:09:28 +0100 [thread overview]
Message-ID: <20171230160928.GB3883@lst.de> (raw)
Hi David and others,
I've recently been refactoring the dma direct mapping and swiotlb
code, and one odd thing I noticed is that the octeon and loongson
swiotlb ops have mb() calls after basically all swiotlb calls.
None of that is explained in either the earlier octeon dma map
commits, nor the commit that added the octeon swiotlb support
(b93b2abce497873be97d765b848e0a955d29f200), and neither in the
loonsoon commit that apparently copy and pasted it
(1299b0e05e106f621fff1504df5251f2a678097e).
Can someone explain what these memory barrier are supposed to do?
next reply other threads:[~2017-12-30 16:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-30 16:09 Christoph Hellwig [this message]
2018-01-02 2:28 ` mb() calls in octeon / loongson swiotlb dma_map_ops Huacai Chen
2018-01-05 1:21 ` David Daney
2018-01-09 18:31 ` Christoph Hellwig
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