From: Arnd Bergmann <arnd@arndb.de>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: iommu@lists.linux-foundation.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
dri-devel@lists.freedesktop.org,
Will Deacon <will.deacon@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Robin Murphy <robin.murphy@arm.com>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Joerg Roedel <joro@8bytes.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Sakari Ailus <sakari.ailus@iki.fi>,
Mark Yao <mark.yao@rock-chips.com>,
Heiko Stuebner <heiko@sntech.de>,
Tomasz Figa <tfiga@chromium.org>, Inki Dae <inki.dae@samsung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Krzysztof Kozlowski <k.kozlowski@samsung.com>
Subject: Re: [RFC 3/3] iommu: dma-iommu: use common implementation also on ARM architecture
Date: Thu, 25 Feb 2016 15:44:44 +0100 [thread overview]
Message-ID: <4895295.FP9RzJmAYS@wuerfel> (raw)
In-Reply-To: <56CEF2E9.5040706@samsung.com>
On Thursday 25 February 2016 13:26:17 Marek Szyprowski wrote:
> >> +}
> >> +
> >> +extern void *arch_alloc_from_atomic_pool(size_t size, struct page **ret_page,
> >> + gfp_t flags);
> >> +extern bool arch_in_atomic_pool(void *start, size_t size);
> >> +extern int arch_free_from_atomic_pool(void *start, size_t size);
> >> +
> >> +
> > doesn't feel completely right yet. In particular the arch_flush_page()
> > interface is probably still too specific to ARM/ARM64 and won't work
> > that way on other architectures.
> >
> > I think it would be better to do this either more generic, or less generic:
> >
> > a) leave the iommu_dma_map_ops definition in the architecture specific
> > code, but make it call helper functions in the drivers/iommu to do all
> > of the really generic parts.
> >
> > b) clarify that this is only applicable to arch/arm and arch/arm64, and
> > unify things further between these two, as they have very similar
> > requirements in the CPU architecture.
>
> Some really generic parts are already in iommu/dma-iommu.c and one can build
> it's own, non-ARM CPU architecture based IOMMU/DMA-mapping code. Initially I
> also wanted to use that generic code on both ARM and ARM64, but it
> turned out
> that both archs, ARM and ARM64 will duplicate 99% of code, which use this
> 'generic' functions. This was the reason why I dedided to move all that
> common code from arch/{arm,arm64}/mm/dma-mapping.c to
> drivers/iommu/dma-iommu-ops.c
>
> I'm not sure if I can design all the changes that need to be made to
> drivers/iommu/dma-iommu-ops.c to make it more generic. Maybe when one will
> try to use that code with other, non-ARM architecture based arch glue code,
> a better abstraction can be developed. For now I would like to keep all this
> code in a common place so both arm and arm64 will benefit from improvements
> done there.
Fair enough. Let's stay with your approach then.
Arnd
next prev parent reply other threads:[~2016-02-25 14:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-19 8:22 [RFC 0/3] Unify IOMMU-based DMA-mapping code for ARM and ARM64 Marek Szyprowski
2016-02-19 8:22 ` [RFC 1/3] drm/exynos: rewrite IOMMU support code Marek Szyprowski
2016-02-19 8:22 ` [RFC 2/3] iommu: dma-iommu: move IOMMU/DMA-mapping code from ARM64 arch to drivers Marek Szyprowski
2016-04-18 2:20 ` Mark yao
2016-02-19 8:22 ` [RFC 3/3] iommu: dma-iommu: use common implementation also on ARM architecture Marek Szyprowski
2016-02-19 10:30 ` Arnd Bergmann
2016-02-25 12:26 ` Marek Szyprowski
2016-02-25 14:44 ` Arnd Bergmann [this message]
2016-03-15 12:33 ` Robin Murphy
2016-03-15 11:18 ` Magnus Damm
2016-03-15 11:45 ` Robin Murphy
2016-03-15 12:03 ` Marek Szyprowski
2016-04-18 2:20 ` Mark yao
2016-04-18 2:18 ` [RFC 0/3] Unify IOMMU-based DMA-mapping code for ARM and ARM64 Mark yao
2016-04-19 3:17 ` [PATCH] drm/rockchip: rewrite IOMMU support code Mark Yao
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