From: Christoph Hellwig <hch@infradead.org>
To: Will Deacon <will@kernel.org>
Cc: janghyuck.kim@samsung.com, catalin.marinas@arm.com,
linux-kernel@vger.kernel.org, hyesoo.yu@samsung.com,
iommu@lists.linux-foundation.org,
Cho KyongHo <pullip.cho@samsung.com>,
robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] dma-mapping: introduce relaxed version of dma sync
Date: Tue, 18 Aug 2020 17:10:06 +0100 [thread overview]
Message-ID: <20200818161006.GA25124@infradead.org> (raw)
In-Reply-To: <20200818100756.GA15543@willie-the-truck>
On Tue, Aug 18, 2020 at 11:07:57AM +0100, Will Deacon wrote:
> > > so I'm not sure
> > > that we should be complicating the implementation like this to try to
> > > make it "fast".
> > >
> > I agree that this patch makes the implementation of dma API a bit more
> > but I don't think this does not impact its complication seriously.
>
> It's death by a thousand cuts; this patch further fragments the architecture
> backends and leads to arm64-specific behaviour which consequently won't get
> well tested by anybody else. Now, it might be worth it, but there's not
> enough information here to make that call.
So it turns out I misread the series (*cough*, crazy long lines,
*cough*), and it does not actually expose a new API as I thought, but
it still makes a total mess of the internal interface. It turns out
that on the for cpu side we already have arch_sync_dma_for_cpu_all,
which should do all that is needed. We could do the equivalent for
the to device side, but only IFF there really is a major benefit for
something that actually is mainstream and matters.
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next prev parent reply other threads:[~2020-08-18 16:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200818075050epcas2p15c780650f5f6b4a54ce731c273d24c98@epcas2p1.samsung.com>
2020-08-18 7:43 ` [PATCH 1/2] dma-mapping: introduce relaxed version of dma sync Cho KyongHo
[not found] ` <CGME20200818075051epcas2p316edad6edd3df59444c08d392b075ea8@epcas2p3.samsung.com>
2020-08-18 7:43 ` [PATCH 2/2] arm64: dma-mapping: add relaxed DMA sync Cho KyongHo
2020-08-18 8:28 ` [PATCH 1/2] dma-mapping: introduce relaxed version of dma sync Will Deacon
2020-08-18 8:37 ` Christoph Hellwig
2020-08-18 9:46 ` Cho KyongHo
2020-08-18 9:37 ` Cho KyongHo
2020-08-18 10:07 ` Will Deacon
2020-08-18 16:10 ` Christoph Hellwig [this message]
2020-08-19 2:01 ` Cho KyongHo
2020-08-19 1:24 ` Cho KyongHo
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