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From: Arnd Bergmann <arnd@arndb.de>
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Subject: Re: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms
Date: Tue, 03 Feb 2015 17:36:59 +0100
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On Tuesday 03 February 2015 11:22:01 Rob Clark wrote:
> On Tue, Feb 3, 2015 at 11:12 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > I agree for the case you are describing here. From what I understood
> > from Rob was that he is looking at something more like:
> >
> > Fig 3
> > CPU--L1cache--L2cache--Memory--IOMMU---<iobus>--device
> >
> > where the IOMMU controls one or more contexts per device, and is
> > shared across GPU and non-GPU devices. Here, we need to use the
> > dmap-mapping interface to set up the IO page table for any device
> > that is unable to address all of system RAM, and we can use it
> > for purposes like isolation of the devices. There are also cases
> > where using the IOMMU is not optional.
> 
> 
> Actually, just to clarify, the IOMMU instance is specific to the GPU..
> not shared with other devices.  Otherwise managing multiple contexts
> would go quite badly..
> 
> But other devices have their own instance of the same IOMMU.. so same
> driver could be used.

I think from the driver perspective, I'd view those two cases as
identical. Not sure if Russell agrees with that.

	Arnd

From mboxrd@z Thu Jan  1 00:00:00 1970
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From: Arnd Bergmann <arnd@arndb.de>
To: linaro-kernel@lists.linaro.org
Cc: Rob Clark <robdclark@gmail.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	Tomasz Stanislawski <stanislawski.tomasz@googlemail.com>,
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Subject: Re: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms
Date: Tue, 03 Feb 2015 17:36:59 +0100
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On Tuesday 03 February 2015 11:22:01 Rob Clark wrote:
> On Tue, Feb 3, 2015 at 11:12 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > I agree for the case you are describing here. From what I understood
> > from Rob was that he is looking at something more like:
> >
> > Fig 3
> > CPU--L1cache--L2cache--Memory--IOMMU---<iobus>--device
> >
> > where the IOMMU controls one or more contexts per device, and is
> > shared across GPU and non-GPU devices. Here, we need to use the
> > dmap-mapping interface to set up the IO page table for any device
> > that is unable to address all of system RAM, and we can use it
> > for purposes like isolation of the devices. There are also cases
> > where using the IOMMU is not optional.
> 
> 
> Actually, just to clarify, the IOMMU instance is specific to the GPU..
> not shared with other devices.  Otherwise managing multiple contexts
> would go quite badly..
> 
> But other devices have their own instance of the same IOMMU.. so same
> driver could be used.

I think from the driver perspective, I'd view those two cases as
identical. Not sure if Russell agrees with that.

	Arnd

From mboxrd@z Thu Jan  1 00:00:00 1970
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From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms
Date: Tue, 03 Feb 2015 17:36:59 +0100
Message-ID: <7233574.nKiRa7HnXU@wuerfel>
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Cc: Rob Clark <robdclark@gmail.com>, Russell King - ARM Linux <linux@arm.linux.org.uk>, Tomasz Stanislawski <stanislawski.tomasz@googlemail.com>, LKML <linux-kernel@vger.kernel.org>, DRI mailing list <dri-devel@lists.freedesktop.org>, "linaro-mm-sig@lists.linaro.org" <linaro-mm-sig@lists.linaro.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Daniel Vetter <daniel@ffwll.ch>, Robin Murphy <robin.murphy@arm.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-media@vger.kernel.org" <linux-media@vger.kernel.org>

On Tuesday 03 February 2015 11:22:01 Rob Clark wrote:
> On Tue, Feb 3, 2015 at 11:12 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > I agree for the case you are describing here. From what I understood
> > from Rob was that he is looking at something more like:
> >
> > Fig 3
> > CPU--L1cache--L2cache--Memory--IOMMU---<iobus>--device
> >
> > where the IOMMU controls one or more contexts per device, and is
> > shared across GPU and non-GPU devices. Here, we need to use the
> > dmap-mapping interface to set up the IO page table for any device
> > that is unable to address all of system RAM, and we can use it
> > for purposes like isolation of the devices. There are also cases
> > where using the IOMMU is not optional.
> 
> 
> Actually, just to clarify, the IOMMU instance is specific to the GPU..
> not shared with other devices.  Otherwise managing multiple contexts
> would go quite badly..
> 
> But other devices have their own instance of the same IOMMU.. so same
> driver could be used.

I think from the driver perspective, I'd view those two cases as
identical. Not sure if Russell agrees with that.

	Arnd

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From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Tue, 03 Feb 2015 17:36:59 +0100
Subject: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing
 attacher constraints with dma-parms
In-Reply-To: <CAF6AEGsttiufoqPbDiZfUX2ndbv2XfeZzcfyaf-AcUJgJpgLkA@mail.gmail.com>
References: <1422347154-15258-1-git-send-email-sumit.semwal@linaro.org>
 <6906596.JU5vQoa1jV@wuerfel>
 <CAF6AEGsttiufoqPbDiZfUX2ndbv2XfeZzcfyaf-AcUJgJpgLkA@mail.gmail.com>
Message-ID: <7233574.nKiRa7HnXU@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tuesday 03 February 2015 11:22:01 Rob Clark wrote:
> On Tue, Feb 3, 2015 at 11:12 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > I agree for the case you are describing here. From what I understood
> > from Rob was that he is looking at something more like:
> >
> > Fig 3
> > CPU--L1cache--L2cache--Memory--IOMMU---<iobus>--device
> >
> > where the IOMMU controls one or more contexts per device, and is
> > shared across GPU and non-GPU devices. Here, we need to use the
> > dmap-mapping interface to set up the IO page table for any device
> > that is unable to address all of system RAM, and we can use it
> > for purposes like isolation of the devices. There are also cases
> > where using the IOMMU is not optional.
> 
> 
> Actually, just to clarify, the IOMMU instance is specific to the GPU..
> not shared with other devices.  Otherwise managing multiple contexts
> would go quite badly..
> 
> But other devices have their own instance of the same IOMMU.. so same
> driver could be used.

I think from the driver perspective, I'd view those two cases as
identical. Not sure if Russell agrees with that.

	Arnd

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing
 attacher constraints with dma-parms
Date: Tue, 03 Feb 2015 17:36:59 +0100
Message-ID: <7233574.nKiRa7HnXU@wuerfel>
References: <1422347154-15258-1-git-send-email-sumit.semwal@linaro.org>
 <6906596.JU5vQoa1jV@wuerfel>
 <CAF6AEGsttiufoqPbDiZfUX2ndbv2XfeZzcfyaf-AcUJgJpgLkA@mail.gmail.com>
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