From: Thierry Reding <thierry.reding@gmail.com>
To: Stephen Warren <swarren@wwwdotorg.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Kumar Gala <galak@codeaurora.org>,
Cho KyongHo <pullip.cho@samsung.com>,
Grant Grundler <grundler@chromium.org>,
Dave Martin <Dave.Martin@arm.com>,
Marc Zyngier <marc.zyngier@arm.com>,
Will Deacon <will.deacon@arm.com>, Joerg Roedel <joro@8bytes.org>,
Hiroshi Doyu <hdoyu@nvidia.com>,
devicetree@vger.kernel.org, iommu@lists.linux-foundation.org,
linux-arm-kernel@lists.infradead.org,
linux-tegra@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] devicetree: Add generic IOMMU device tree bindings
Date: Fri, 30 May 2014 09:30:08 +0200 [thread overview]
Message-ID: <20140530073006.GA24748@ulmo> (raw)
In-Reply-To: <538757B6.4010109@wwwdotorg.org>
[-- Attachment #1: Type: text/plain, Size: 2658 bytes --]
On Thu, May 29, 2014 at 09:52:22AM -0600, Stephen Warren wrote:
> On 05/23/2014 02:36 PM, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> >
> > This commit introduces a generic device tree binding for IOMMU devices.
> > Only a very minimal subset is described here, but it is enough to cover
> > the requirements of both the Exynos System MMU and Tegra SMMU as
> > discussed here:
> >
> > https://lkml.org/lkml/2014/4/27/346
> >
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> > Apologies for the noise, but apparently I mistyped one of the email
> > addresses, should be fixed now.
> >
> > Changes in v2:
> > - add notes about "dma-ranges" property (drop note from commit message)
> > - document priorities of "iommus" property vs. "dma-ranges" property
> > - drop #iommu-cells in favour of #address-cells and #size-cells
>
> I think this is a mistake. address-cells/size-cells are for transactions
> flowing down the bus (from the CPU to date). Describing a connection
> from a device to an IOMMU is something completely different, and should
> therefore simply use an iommu-cells property to describe any necessary
> information. If we start re-using properties for different things in
> different contexts, how is anyone going to know what they mean, and how
> will conflicts be resolved. For example, what if there's a single HW
> module that both acts as a regular register bus with children (where
> address-cells/size-cells defines how transactions reach the children
> from the parent), and is also an IOMMU (where according to this binding
> proposal, address-cells/size-cells represent some aspect of the IOMMU
> feature). Using different properties for different things is the only
> sane way to keep different concepts separate. Another alternative would
> be to represent the single HW module as separate nodes in DT, but I
> think that will only make our lives harder, and where I've done that in
> the past, I've regretted it.
There was some back-and-forth on this topic and the latest concensus
when I wrote the second version was that #address-cells and #size-cells
were to be used.
But there was some bore back-and-forth after that, and it seems like
Arnd no longer thinks that using #address-cells and #size-cells is a
good idea either[0].
Arnd, can you take another look at this binding and see if there's
anything else missing? If not I'll go through the document again and
update all #address-cells/#size-cells references with #iommu-cells as
appropriate and submit v3.
Thanks,
Thierry
[0]: https://lkml.org/lkml/2014/5/20/609
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WARNING: multiple messages have this Message-ID (diff)
From: thierry.reding@gmail.com (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] devicetree: Add generic IOMMU device tree bindings
Date: Fri, 30 May 2014 09:30:08 +0200 [thread overview]
Message-ID: <20140530073006.GA24748@ulmo> (raw)
In-Reply-To: <538757B6.4010109@wwwdotorg.org>
On Thu, May 29, 2014 at 09:52:22AM -0600, Stephen Warren wrote:
> On 05/23/2014 02:36 PM, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> >
> > This commit introduces a generic device tree binding for IOMMU devices.
> > Only a very minimal subset is described here, but it is enough to cover
> > the requirements of both the Exynos System MMU and Tegra SMMU as
> > discussed here:
> >
> > https://lkml.org/lkml/2014/4/27/346
> >
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> > Apologies for the noise, but apparently I mistyped one of the email
> > addresses, should be fixed now.
> >
> > Changes in v2:
> > - add notes about "dma-ranges" property (drop note from commit message)
> > - document priorities of "iommus" property vs. "dma-ranges" property
> > - drop #iommu-cells in favour of #address-cells and #size-cells
>
> I think this is a mistake. address-cells/size-cells are for transactions
> flowing down the bus (from the CPU to date). Describing a connection
> from a device to an IOMMU is something completely different, and should
> therefore simply use an iommu-cells property to describe any necessary
> information. If we start re-using properties for different things in
> different contexts, how is anyone going to know what they mean, and how
> will conflicts be resolved. For example, what if there's a single HW
> module that both acts as a regular register bus with children (where
> address-cells/size-cells defines how transactions reach the children
> from the parent), and is also an IOMMU (where according to this binding
> proposal, address-cells/size-cells represent some aspect of the IOMMU
> feature). Using different properties for different things is the only
> sane way to keep different concepts separate. Another alternative would
> be to represent the single HW module as separate nodes in DT, but I
> think that will only make our lives harder, and where I've done that in
> the past, I've regretted it.
There was some back-and-forth on this topic and the latest concensus
when I wrote the second version was that #address-cells and #size-cells
were to be used.
But there was some bore back-and-forth after that, and it seems like
Arnd no longer thinks that using #address-cells and #size-cells is a
good idea either[0].
Arnd, can you take another look at this binding and see if there's
anything else missing? If not I'll go through the document again and
update all #address-cells/#size-cells references with #iommu-cells as
appropriate and submit v3.
Thanks,
Thierry
[0]: https://lkml.org/lkml/2014/5/20/609
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next prev parent reply other threads:[~2014-05-30 7:30 UTC|newest]
Thread overview: 215+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-23 20:36 [PATCH v2] devicetree: Add generic IOMMU device tree bindings Thierry Reding
2014-05-23 20:36 ` Thierry Reding
2014-05-23 20:36 ` Thierry Reding
[not found] ` <1400877395-4235-1-git-send-email-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-05-29 15:52 ` Stephen Warren
2014-05-29 15:52 ` Stephen Warren
2014-05-29 15:52 ` Stephen Warren
2014-05-30 7:30 ` Thierry Reding [this message]
2014-05-30 7:30 ` Thierry Reding
2014-05-30 11:27 ` Dave Martin
2014-05-30 11:27 ` Dave Martin
2014-05-30 11:27 ` Dave Martin
[not found] ` <20140530112728.GB3949-M5GwZQ6tE7x5pKCnmE3YQBJ8xKzm50AiAL8bYrjMMd8@public.gmane.org>
2014-05-30 19:11 ` Arnd Bergmann
2014-05-30 19:11 ` Arnd Bergmann
2014-05-30 19:11 ` Arnd Bergmann
2014-06-02 10:56 ` Dave Martin
2014-06-02 10:56 ` Dave Martin
2014-06-02 10:56 ` Dave Martin
2014-06-04 21:12 ` Thierry Reding
2014-06-04 21:12 ` Thierry Reding
2014-06-04 21:12 ` Thierry Reding
2014-06-16 12:57 ` Will Deacon
2014-06-16 12:57 ` Will Deacon
2014-06-16 12:57 ` Will Deacon
2014-06-17 11:58 ` Thierry Reding
2014-06-17 11:58 ` Thierry Reding
2014-06-17 11:58 ` Thierry Reding
2014-06-17 12:18 ` Will Deacon
2014-06-17 12:18 ` Will Deacon
2014-06-17 12:18 ` Will Deacon
2014-06-17 23:37 ` Thierry Reding
2014-06-17 23:37 ` Thierry Reding
2014-06-17 23:37 ` Thierry Reding
2014-06-18 10:14 ` Will Deacon
2014-06-18 10:14 ` Will Deacon
2014-06-18 10:14 ` Will Deacon
[not found] ` <20140618101439.GF32699-5wv7dgnIgG8@public.gmane.org>
2014-06-20 15:53 ` Arnd Bergmann
2014-06-20 15:53 ` Arnd Bergmann
2014-06-20 15:53 ` Arnd Bergmann
2014-06-20 17:50 ` Will Deacon
2014-06-20 17:50 ` Will Deacon
2014-06-20 17:50 ` Will Deacon
2014-06-20 18:55 ` Arnd Bergmann
2014-06-20 18:55 ` Arnd Bergmann
2014-06-20 18:55 ` Arnd Bergmann
2014-05-30 11:22 ` Dave Martin
2014-05-30 11:22 ` Dave Martin
2014-05-30 11:22 ` Dave Martin
[not found] ` <20140530112226.GA3949-M5GwZQ6tE7x5pKCnmE3YQBJ8xKzm50AiAL8bYrjMMd8@public.gmane.org>
2014-05-30 19:01 ` Arnd Bergmann
2014-05-30 19:01 ` Arnd Bergmann
2014-05-30 19:01 ` Arnd Bergmann
2014-06-02 11:44 ` Dave Martin
2014-06-02 11:44 ` Dave Martin
2014-06-02 11:44 ` Dave Martin
2014-06-04 21:32 ` Thierry Reding
2014-06-04 21:32 ` Thierry Reding
2014-06-04 21:32 ` Thierry Reding
2014-06-05 9:42 ` Arnd Bergmann
2014-06-05 9:42 ` Arnd Bergmann
2014-06-05 9:42 ` Arnd Bergmann
-- strict thread matches above, loose matches on Subject: below --
2014-06-06 22:45 Thierry Reding
2014-06-06 22:45 ` Thierry Reding
2014-06-07 13:22 ` Arnd Bergmann
2014-06-07 13:22 ` Arnd Bergmann
2014-06-07 13:22 ` Arnd Bergmann
2014-06-09 10:49 ` Thierry Reding
2014-06-09 10:49 ` Thierry Reding
2014-06-09 10:49 ` Thierry Reding
2014-05-23 20:33 Thierry Reding
[not found] ` <1400877218-4113-1-git-send-email-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-05-30 13:16 ` Rob Herring
2014-05-30 13:16 ` Rob Herring
2014-05-30 13:16 ` Rob Herring
[not found] ` <CAL_JsqKumG1PSFoVfeGpLLG+MjXFeF4aUjun=vv1BJpaxk0Byg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-05-30 19:06 ` Arnd Bergmann
2014-05-30 19:06 ` Arnd Bergmann
2014-05-30 19:06 ` Arnd Bergmann
2014-05-30 19:29 ` Hiroshi Doyu
2014-05-30 19:29 ` Hiroshi Doyu
2014-05-30 19:29 ` Hiroshi Doyu
2014-05-30 19:54 ` Arnd Bergmann
2014-05-30 19:54 ` Arnd Bergmann
2014-05-30 19:54 ` Arnd Bergmann
2014-06-01 9:55 ` Will Deacon
2014-06-01 9:55 ` Will Deacon
2014-06-01 9:55 ` Will Deacon
[not found] ` <20140601095546.GA8625-5wv7dgnIgG8@public.gmane.org>
2014-06-04 13:39 ` Thierry Reding
2014-06-04 13:39 ` Thierry Reding
2014-06-04 13:39 ` Thierry Reding
2014-06-04 13:44 ` Thierry Reding
2014-06-04 13:44 ` Thierry Reding
2014-06-04 13:44 ` Thierry Reding
2014-06-04 13:53 ` Arnd Bergmann
2014-06-04 13:53 ` Arnd Bergmann
2014-06-04 13:53 ` Arnd Bergmann
2014-06-04 13:56 ` Will Deacon
2014-06-04 13:56 ` Will Deacon
2014-06-04 13:56 ` Will Deacon
[not found] ` <20140604135600.GD6644-5wv7dgnIgG8@public.gmane.org>
2014-06-04 14:01 ` Arnd Bergmann
2014-06-04 14:01 ` Arnd Bergmann
2014-06-04 14:01 ` Arnd Bergmann
2014-06-04 16:39 ` Will Deacon
2014-06-04 16:39 ` Will Deacon
2014-06-04 16:39 ` Will Deacon
2014-05-30 19:31 ` Rob Herring
2014-05-30 19:31 ` Rob Herring
2014-05-30 19:31 ` Rob Herring
[not found] ` <CAL_Jsq+tkFNpjSEZboT+o69B_Z3a8e-ZVKaYDmLwtkyYoPy6VQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-05-30 19:49 ` Arnd Bergmann
2014-05-30 19:49 ` Arnd Bergmann
2014-05-30 19:49 ` Arnd Bergmann
2014-06-02 10:41 ` Dave Martin
2014-06-02 10:41 ` Dave Martin
2014-06-02 10:41 ` Dave Martin
[not found] ` <20140602104104.GD3855-M5GwZQ6tE7x5pKCnmE3YQBJ8xKzm50AiAL8bYrjMMd8@public.gmane.org>
2014-06-04 14:35 ` Thierry Reding
2014-06-04 14:35 ` Thierry Reding
2014-06-04 14:35 ` Thierry Reding
2014-06-04 16:41 ` Will Deacon
2014-06-04 16:41 ` Will Deacon
2014-06-04 16:41 ` Will Deacon
[not found] ` <20140604164132.GF6644-5wv7dgnIgG8@public.gmane.org>
2014-06-04 21:00 ` Thierry Reding
2014-06-04 21:00 ` Thierry Reding
2014-06-04 21:00 ` Thierry Reding
2014-06-05 19:10 ` Varun Sethi
2014-06-05 19:10 ` Varun Sethi
2014-06-05 19:10 ` Varun Sethi
2014-06-16 15:27 ` Will Deacon
2014-06-16 15:27 ` Will Deacon
2014-06-16 15:27 ` Will Deacon
[not found] ` <20140616152739.GS16758-5wv7dgnIgG8@public.gmane.org>
2014-06-16 16:56 ` Stuart Yoder
2014-06-16 16:56 ` Stuart Yoder
2014-06-16 16:56 ` Stuart Yoder
[not found] ` <8b0492b4697943a0b1f276ef42cc8223-ufbTtyGzTTT8GZusEWM6WuO6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-06-16 17:04 ` Will Deacon
2014-06-16 17:04 ` Will Deacon
2014-06-16 17:04 ` Will Deacon
[not found] ` <20140616170416.GA16758-5wv7dgnIgG8@public.gmane.org>
2014-06-16 17:30 ` Arnd Bergmann
2014-06-16 17:30 ` Arnd Bergmann
2014-06-16 17:30 ` Arnd Bergmann
2014-06-16 18:53 ` Stuart Yoder
2014-06-16 18:53 ` Stuart Yoder
2014-06-16 18:53 ` Stuart Yoder
[not found] ` <419e67f783524d208ab3be16bcd94bd9-ufbTtyGzTTT8GZusEWM6WuO6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-06-17 10:26 ` Varun Sethi
2014-06-17 10:26 ` Varun Sethi
2014-06-17 10:26 ` Varun Sethi
[not found] ` <0587e1f4894546398be0798d2bc2c84f-AZ66ij2kwaacCcN9WK45f+O6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-06-17 10:43 ` Will Deacon
2014-06-17 10:43 ` Will Deacon
2014-06-17 10:43 ` Will Deacon
[not found] ` <20140617104304.GD13808-5wv7dgnIgG8@public.gmane.org>
2014-06-17 11:21 ` Varun Sethi
2014-06-17 11:21 ` Varun Sethi
2014-06-17 11:21 ` Varun Sethi
[not found] ` <32165315f0b84be9948f489fd87bf6a9-AZ66ij2kwaacCcN9WK45f+O6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-06-17 14:50 ` Stuart Yoder
2014-06-17 14:50 ` Stuart Yoder
2014-06-17 14:50 ` Stuart Yoder
2014-06-18 9:29 ` Will Deacon
2014-06-18 9:29 ` Will Deacon
2014-06-18 9:29 ` Will Deacon
2014-06-17 14:39 ` Stuart Yoder
2014-06-17 14:39 ` Stuart Yoder
2014-06-17 14:39 ` Stuart Yoder
2014-06-20 23:16 ` Olav Haugan
2014-06-20 23:16 ` Olav Haugan
2014-06-20 23:16 ` Olav Haugan
2014-06-24 9:18 ` Will Deacon
2014-06-24 9:18 ` Will Deacon
2014-06-24 9:18 ` Will Deacon
[not found] ` <20140624091808.GC26013-5wv7dgnIgG8@public.gmane.org>
2014-06-24 17:57 ` Olav Haugan
2014-06-24 17:57 ` Olav Haugan
2014-06-24 17:57 ` Olav Haugan
2014-06-24 18:11 ` Will Deacon
2014-06-24 18:11 ` Will Deacon
2014-06-24 18:11 ` Will Deacon
[not found] ` <20140624181150.GB4067-5wv7dgnIgG8@public.gmane.org>
2014-06-24 18:20 ` Arnd Bergmann
2014-06-24 18:20 ` Arnd Bergmann
2014-06-24 18:20 ` Arnd Bergmann
2014-06-25 9:17 ` Will Deacon
2014-06-25 9:17 ` Will Deacon
2014-06-25 9:17 ` Will Deacon
2014-06-25 9:27 ` Arnd Bergmann
2014-06-25 9:27 ` Arnd Bergmann
2014-06-25 9:27 ` Arnd Bergmann
2014-06-25 9:38 ` Will Deacon
2014-06-25 9:38 ` Will Deacon
2014-06-25 9:38 ` Will Deacon
2014-06-25 9:48 ` Arnd Bergmann
2014-06-25 9:48 ` Arnd Bergmann
2014-06-25 9:48 ` Arnd Bergmann
2014-06-25 9:57 ` Will Deacon
2014-06-25 9:57 ` Will Deacon
2014-06-25 9:57 ` Will Deacon
[not found] ` <20140625095735.GI6153-5wv7dgnIgG8@public.gmane.org>
2014-06-25 10:12 ` Arnd Bergmann
2014-06-25 10:12 ` Arnd Bergmann
2014-06-25 10:12 ` Arnd Bergmann
2014-06-25 10:14 ` Will Deacon
2014-06-25 10:14 ` Will Deacon
2014-06-25 10:14 ` Will Deacon
2014-06-24 21:35 ` Olav Haugan
2014-06-24 21:35 ` Olav Haugan
2014-06-24 21:35 ` Olav Haugan
[not found] ` <53A9EF3A.2070704-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2014-06-25 9:18 ` Will Deacon
2014-06-25 9:18 ` Will Deacon
2014-06-25 9:18 ` Will Deacon
[not found] ` <20140625091858.GG6153-5wv7dgnIgG8@public.gmane.org>
2014-06-27 22:23 ` Olav Haugan
2014-06-27 22:23 ` Olav Haugan
2014-06-27 22:23 ` Olav Haugan
[not found] ` <53ADEEDF.7060902-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2014-06-30 9:52 ` Will Deacon
2014-06-30 9:52 ` Will Deacon
2014-06-30 9:52 ` Will Deacon
2014-07-09 1:07 ` Olav Haugan
2014-07-09 1:07 ` Olav Haugan
2014-07-09 1:07 ` Olav Haugan
[not found] ` <53BC95DA.1010500-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2014-07-09 10:54 ` Will Deacon
2014-07-09 10:54 ` Will Deacon
2014-07-09 10:54 ` Will Deacon
[not found] ` <20140709105441.GE9485-5wv7dgnIgG8@public.gmane.org>
2014-07-10 22:32 ` Olav Haugan
2014-07-10 22:32 ` Olav Haugan
2014-07-10 22:32 ` Olav Haugan
2014-07-11 12:24 ` Will Deacon
2014-07-11 12:24 ` Will Deacon
2014-07-11 12:24 ` Will Deacon
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