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From: Arnd Bergmann <arnd@kernel.org>
To: Sven Peter <sven@svenpeter.dev>
Cc: Rob Herring <robh@kernel.org>, DTML <devicetree@vger.kernel.org>,
	Will Deacon <will@kernel.org>, Hector Martin <marcan@marcan.st>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
	Marc Zyngier <maz@kernel.org>,
	Mohamed Mediouni <mohamed.mediouni@caramail.com>,
	Stan Skowronek <stan@corellium.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: [PATCH 0/3] Apple M1 DART IOMMU driver
Date: Thu, 25 Mar 2021 22:41:09 +0100	[thread overview]
Message-ID: <CAK8P3a0fvnYLrG=cGiOQ6u8aZnriTeM0R=MW7FX=94mO13Rq0w@mail.gmail.com> (raw)
In-Reply-To: <43685c67-6d9c-4e72-b320-0462c2273bf0@www.fastmail.com>

On Thu, Mar 25, 2021 at 8:53 AM Sven Peter <sven@svenpeter.dev> wrote:
> On Tue, Mar 23, 2021, at 21:53, Rob Herring wrote:
>
> I'm probably just confused or maybe the documentation is outdated but I don't
> see how I could specify "this device can only use DMA addresses from
> 0x00100000...0x3ff00000 but can map these via the iommu to any physical
> address" using 'dma-ranges'.

It sounds like this is a holdover from the original powerpc iommu, which also
had a limited set of virtual addresses in the iommu.

I would think it's sufficient to describe it in the iommu itself,
since the limitation
is more "addresses coming into the iommu must be this range" than "this device
must use that address range for talking to the iommu".

If the addresses are allocated by the iommu driver, and each iommu only has
one DMA master attached to it, having a simple range property in the iommu
node should do the trick here. If there might be multiple devices on the same
iommu but with different address ranges (which I don't think is the case), then
it could be part of the reference to the iommu.

         Arnd
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  parent reply	other threads:[~2021-03-25 21:41 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-20 15:19 [PATCH 0/3] Apple M1 DART IOMMU driver Sven Peter via iommu
2021-03-20 15:19 ` [PATCH 1/3] iommu: io-pgtable: add DART pagetable format Sven Peter via iommu
2021-03-24 16:37   ` Robin Murphy
2021-03-25 20:47     ` Sven Peter via iommu
2021-03-20 15:20 ` [PATCH 2/3] dt-bindings: iommu: add DART iommu bindings Sven Peter via iommu
2021-03-22  0:15   ` Rob Herring
2021-03-22 18:16     ` Sven Peter via iommu
2021-03-21 16:00 ` [PATCH 0/3] Apple M1 DART IOMMU driver Mark Kettenis
2021-03-21 17:22   ` Sven Peter via iommu
2021-03-21 18:35     ` Mark Kettenis
2021-03-22 22:17       ` Sven Peter via iommu
2021-03-23 20:00         ` Mark Kettenis
2021-03-23 21:03           ` Sven Peter via iommu
2021-03-21 17:28   ` Sven Peter via iommu
2021-03-23 20:53   ` Rob Herring
2021-03-23 22:33     ` Mark Kettenis
2021-03-25  7:53     ` Sven Peter via iommu
2021-03-25 11:50       ` Robin Murphy
2021-03-25 20:49         ` Sven Peter via iommu
2021-03-27 15:33         ` Sven Peter via iommu
2021-03-25 21:41       ` Arnd Bergmann [this message]
2021-03-26 15:59         ` Mark Kettenis
2021-03-26 16:09           ` Arnd Bergmann
2021-03-26 16:10           ` Sven Peter via iommu
2021-03-26 16:38             ` Arnd Bergmann
2021-03-26 17:06               ` Sven Peter via iommu
2021-03-26 17:26               ` Mark Kettenis
2021-03-26 17:34                 ` Robin Murphy
2021-03-26 17:51                   ` Sven Peter via iommu
2021-03-26 19:59                     ` Arnd Bergmann
2021-03-26 21:16                       ` Mark Kettenis
2021-03-27 15:30                       ` Sven Peter via iommu
2021-03-26 20:03                 ` Arnd Bergmann
2021-03-26 21:13                   ` Mark Kettenis
2021-03-24 15:29 ` Robin Murphy
2021-03-25  7:58   ` Sven Peter via iommu

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