From: Christoph Hellwig <hch@lst.de>
To: iommu@lists.linux-foundation.org
Cc: Guan Xuetao <gxt@pku.edu.cn>, Shawn Anastasio <shawn@anastas.io>,
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>,
Geert Uytterhoeven <geert@linux-m68k.org>,
linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org
Subject: [PATCH 6/6] MIPS: document mixing "slightly different CCAs"
Date: Mon, 26 Aug 2019 15:25:53 +0200 [thread overview]
Message-ID: <20190826132553.4116-7-hch@lst.de> (raw)
In-Reply-To: <20190826132553.4116-1-hch@lst.de>
Based on an email from Paul Burton, quoting section 4.8 "Cacheability and
Coherency Attributes and Access Types" of "MIPS Architecture Volume 1:
Introduction to the MIPS32 Architecture" (MD00080, revision 6.01).
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/mips/Kconfig | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index fc88f68ea1ee..aff1cadeea43 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1119,6 +1119,13 @@ config DMA_PERDEV_COHERENT
config DMA_NONCOHERENT
bool
+ #
+ # MIPS allows mixing "slightly different" Cacheability and Coherency
+ # Attribute bits. It is believed that the uncached access through
+ # KSEG1 and the implementation specific "uncached accelerated" used
+ # by pgprot_writcombine can be mixed, and the latter sometimes provides
+ # significant advantages.
+ #
select ARCH_HAS_DMA_WRITE_COMBINE
select ARCH_HAS_SYNC_DMA_FOR_DEVICE
select ARCH_HAS_UNCACHED_SEGMENT
--
2.20.1
next prev parent reply other threads:[~2019-08-26 13:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 13:25 cleanup the dma_pgprot handling v2 Christoph Hellwig
2019-08-26 13:25 ` [PATCH 1/6] unicore32: remove the unused pgprot_dmacoherent define Christoph Hellwig
2019-08-26 13:25 ` [PATCH 2/6] arm-nommu: " Christoph Hellwig
2019-08-26 13:25 ` [PATCH 3/6] dma-mapping: remove arch_dma_mmap_pgprot Christoph Hellwig
2019-08-27 10:02 ` Paul Burton
2019-08-26 13:25 ` [PATCH 4/6] dma-mapping: make dma_atomic_pool_init self-contained Christoph Hellwig
2019-08-26 13:25 ` [PATCH 5/6] arm64: document the choice of page attributes for pgprot_dmacoherent Christoph Hellwig
2019-08-26 13:25 ` Christoph Hellwig [this message]
2019-08-27 10:03 ` [PATCH 6/6] MIPS: document mixing "slightly different CCAs" Paul Burton
2019-08-29 15:28 ` cleanup the dma_pgprot handling v2 Christoph Hellwig
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