From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org,
Shawn Anastasio <shawn@anastas.io>,
Michael Ellerman <mpe@ellerman.id.au>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Paul Burton <paul.burton@mips.com>,
James Hogan <jhogan@kernel.org>,
linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE
Date: Wed, 18 Sep 2019 20:50:01 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.1909182001260.31718@eddie.linux-mips.org> (raw)
In-Reply-To: <20190807061602.31217-3-hch@lst.de>
On Wed, 7 Aug 2019, Christoph Hellwig wrote:
> Mips uses the KSEG1 kernel memory segment to map dma coherent
> allocations for non-coherent devices as uncacheable, and does not have
> any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation
> path. Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will
> lead to multiple mappings with different caching attributes.
FYI, AFAIK _CACHE_UNCACHED_ACCELERATED (where supported) is effectively
write-combine. Though IIUC someone would have to wire it in first.
Maciej
next prev parent reply other threads:[~2019-09-18 19:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 6:16 fix default dma_mmap_* pgprot v3 Christoph Hellwig
2019-08-07 6:16 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
2019-08-07 6:16 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
2019-09-18 19:50 ` Maciej W. Rozycki [this message]
-- strict thread matches above, loose matches on Subject: below --
2019-08-05 8:01 fix default dma_mmap_* pgprot v2 Christoph Hellwig
2019-08-05 8:01 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
2019-08-05 8:06 ` Sergei Shtylyov
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