From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Rob Clark <robdclark@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
"linaro-mm-sig@lists.linaro.org" <linaro-mm-sig@lists.linaro.org>,
Linaro Kernel Mailman List <linaro-kernel@lists.linaro.org>,
Robin Murphy <robin.murphy@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
DRI mailing list <dri-devel@lists.freedesktop.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Daniel Vetter <daniel@ffwll.ch>,
Tomasz Stanislawski <stanislawski.tomasz@googlemail.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: Re: [Linaro-mm-sig] [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms
Date: Tue, 3 Feb 2015 17:01:46 +0000 [thread overview]
Message-ID: <20150203170146.GX8656@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAF6AEGsttiufoqPbDiZfUX2ndbv2XfeZzcfyaf-AcUJgJpgLkA@mail.gmail.com>
On Tue, Feb 03, 2015 at 11:22:01AM -0500, 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.
Okay, so that is my Fig.2 case, and we don't have to worry about Fig.3.
One thing I forgot in Fig.1/2 which my original did have were to mark
the system MMU as optional. (Think an ARM64 with SMMU into a 32-bit
peripheral bus.) Do we support stacked MMUs in the DMA API? We may
need to if we keep IOMMUs in the DMA API.
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2015-02-03 17:02 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-27 8:25 [RFCv3 1/2] device: add dma_params->max_segment_count Sumit Semwal
2015-01-27 8:25 ` [RFCv3 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms Sumit Semwal
2015-01-29 14:16 ` Maarten Lankhorst
2015-01-29 14:39 ` Russell King - ARM Linux
2015-01-29 15:30 ` Sumit Semwal
2015-01-29 15:47 ` Russell King - ARM Linux
2015-01-29 16:55 ` Sumit Semwal
2015-01-29 18:52 ` Rob Clark
2015-01-29 19:26 ` Russell King - ARM Linux
2015-01-29 22:18 ` Rob Clark
2015-01-29 22:31 ` Russell King - ARM Linux
2015-01-29 23:19 ` Rob Clark
2015-02-02 16:54 ` Daniel Vetter
2015-02-02 20:30 ` Rob Clark
2015-02-02 21:46 ` Russell King - ARM Linux
2015-02-02 22:36 ` Rob Clark
2015-02-03 7:50 ` Daniel Vetter
2015-02-03 7:46 ` Daniel Vetter
2015-02-03 7:48 ` Daniel Vetter
2015-02-03 12:28 ` Russell King - ARM Linux
2015-02-03 13:00 ` Daniel Vetter
2015-02-03 13:28 ` Christian Gmeiner
2015-02-03 14:32 ` Russell King - ARM Linux
2015-02-03 14:25 ` Rob Clark
2015-02-03 14:04 ` Rob Clark
2015-02-03 14:17 ` Arnd Bergmann
2015-02-03 14:41 ` Russell King - ARM Linux
2015-02-03 14:52 ` Arnd Bergmann
2015-02-03 15:22 ` Russell King - ARM Linux
2015-02-03 15:31 ` [Linaro-mm-sig] " Arnd Bergmann
2015-02-03 15:54 ` Russell King - ARM Linux
2015-02-03 16:12 ` Arnd Bergmann
2015-02-03 16:22 ` Rob Clark
2015-02-03 16:36 ` Arnd Bergmann
2015-02-03 20:04 ` Daniel Vetter
2015-02-03 21:42 ` Arnd Bergmann
2015-02-03 22:07 ` Daniel Vetter
2015-02-04 0:14 ` Russell King - ARM Linux
2015-02-03 17:01 ` Russell King - ARM Linux [this message]
2015-02-03 16:58 ` Russell King - ARM Linux
2015-02-03 17:35 ` Rob Clark
2015-02-03 20:08 ` Daniel Vetter
2015-02-03 21:44 ` Arnd Bergmann
2015-02-03 15:25 ` Rob Clark
2015-02-03 15:19 ` Rob Clark
2015-02-03 14:37 ` Russell King - ARM Linux
2015-02-03 14:44 ` Rob Clark
2015-02-03 14:58 ` Russell King - ARM Linux
2015-02-02 5:53 ` Sumit Semwal
2015-02-11 8:28 ` Marek Szyprowski
2015-02-11 11:12 ` Russell King - ARM Linux
2015-02-11 11:23 ` Rob Clark
2015-02-11 12:56 ` Daniel Vetter
2015-02-11 13:30 ` Rob Clark
2015-02-11 12:20 ` Marek Szyprowski
2015-02-11 16:23 ` Russell King - ARM Linux
2015-05-05 14:41 ` Sumit Semwal
2015-06-03 6:39 ` [Linaro-mm-sig] " Hans Verkuil
2015-06-03 8:41 ` Russell King - ARM Linux
2015-06-03 9:37 ` Hans Verkuil
2015-06-04 5:24 ` Sumit Semwal
2015-01-28 14:09 ` [RFCv3 1/2] device: add dma_params->max_segment_count Marek Szyprowski
2015-06-03 6:13 ` [Linaro-mm-sig] " Hans Verkuil
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