From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] devicetree: Add generic IOMMU device tree bindings
Date: Fri, 30 May 2014 21:01:19 +0200 [thread overview]
Message-ID: <4830064.JvgTAs8Xty@wuerfel> (raw)
In-Reply-To: <20140530112226.GA3949@e103592.cambridge.arm.com>
On Friday 30 May 2014 12:22:32 Dave Martin wrote:
> > +
> > +Examples:
> > +=========
> > +
> > +Single-master IOMMU:
> > +--------------------
> > +
> > + iommu {
> > + #address-cells = <0>;
> > + #size-cells = <0>;
> > + };
> > +
> > + master {
> > + iommus = <&/iommu>;
> > + };
> > +
> > +Multiple-master IOMMU with fixed associations:
> > +----------------------------------------------
> > +
> > + /* multiple-master IOMMU */
> > + iommu {
> > + /*
> > + * Masters are statically associated with this IOMMU and
> > + * address translation is always enabled.
> > + */
> > + #address-cells = <0>;
> > + #size-cells = <0>;
>
> In this example, can different translations be set up for the different
> masters?
>
> With no cells available to contain any sort of ID, it looks like this
> is not possible.
Correct, this example is for an IOMMU that does not use IDs but has a
shared address space for all devices.
> > +Multiple-master IOMMU with configurable DMA window:
> > +---------------------------------------------------
> > +
> > + / {
> > + #address-cells = <1>;
> > + #size-cells = <1>;
> > +
> > + iommu {
> > + /* master ID, address of DMA window */
> > + #address-cells = <2>;
> > + #size-cells = <2>;
> > + };
> > +
> > + master {
> > + /* master ID 42, 4 GiB DMA window starting at 0 */
> > + iommus = <&/iommu 42 0 0x1 0x0>;
>
> I'm still concerned that in order to deal with future cases we will have
> to invent multiple ways to parse the "iommus" property. For example, if
> we have a PCEe RC mastering through an IOMMU, it will pass a huge set
> of possible master IDs to the IOMMU, not just noe or two.
>
> Do you have a solution in mind for that which doesn't break backwards
> compatibility?
I think we can treat PCI as a special case here and have an interface
that gets used by the PCI core code to talk to the IOMMU core code
when setting up a the dma_map_ops for a PCI function. As long as the
IOMMU driver understands what PCI is, we don't have to describe the
mapping in detail.
> One option is to include an extra cell to the IOMMUs property
> that indicates how to parse it. For now, only a single value would
> be defined. For example:
>
> iommus = <&/iommu IOMMU_SIMPLE 42>;
>
> Then maybe later
>
> iommus = <&/iommu IOMMU_RANGE 0x10000 0x10000>;
>
> (I'm not suggesting what IOMMU_RANGE might mean.)
>
This can really be left up to the specific IOMMU driver itself.
We can have drivers that support both #address-cells=<1>
and #address-cells=<2> and behave differently based on that.
I don't see a reason to define that across IOMMU implementations.
> Other options are to introduce a new property name
>
> range-iommus = <&/iommu 0x10000 0x10000>;
>
> or control the parsing of incompatible iommus properties via a compatible
> string somewhere.
Introducing a new compatible string is always an option as the last resort.
Arnd
next prev parent reply other threads:[~2014-05-30 19:01 UTC|newest]
Thread overview: 71+ 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
2014-05-29 15:52 ` Stephen Warren
2014-05-30 7:30 ` Thierry Reding
2014-05-30 11:27 ` Dave Martin
2014-05-30 19:11 ` Arnd Bergmann
2014-06-02 10:56 ` Dave Martin
2014-06-04 21:12 ` Thierry Reding
2014-06-16 12:57 ` Will Deacon
2014-06-17 11:58 ` Thierry Reding
2014-06-17 12:18 ` Will Deacon
2014-06-17 23:37 ` Thierry Reding
2014-06-18 10:14 ` Will Deacon
2014-06-20 15:53 ` Arnd Bergmann
2014-06-20 17:50 ` Will Deacon
2014-06-20 18:55 ` Arnd Bergmann
2014-05-30 11:22 ` Dave Martin
2014-05-30 19:01 ` Arnd Bergmann [this message]
2014-06-02 11:44 ` Dave Martin
2014-06-04 21:32 ` Thierry Reding
2014-06-05 9:42 ` Arnd Bergmann
[not found] <1400877218-4113-1-git-send-email-thierry.reding@gmail.com>
2014-05-30 13:16 ` Rob Herring
2014-05-30 19:06 ` Arnd Bergmann
2014-05-30 19:29 ` Hiroshi Doyu
2014-05-30 19:54 ` Arnd Bergmann
2014-06-01 9:55 ` Will Deacon
2014-06-04 13:39 ` Thierry Reding
2014-06-04 13:44 ` Thierry Reding
2014-06-04 13:53 ` Arnd Bergmann
2014-06-04 13:56 ` Will Deacon
2014-06-04 14:01 ` Arnd Bergmann
2014-06-04 16:39 ` Will Deacon
2014-05-30 19:31 ` Rob Herring
2014-05-30 19:49 ` Arnd Bergmann
2014-06-02 10:41 ` Dave Martin
2014-06-04 14:35 ` Thierry Reding
2014-06-04 16:41 ` Will Deacon
2014-06-04 21:00 ` Thierry Reding
2014-06-05 19:10 ` Varun Sethi
2014-06-16 15:27 ` Will Deacon
2014-06-16 16:56 ` Stuart Yoder
2014-06-16 17:04 ` Will Deacon
2014-06-16 17:30 ` Arnd Bergmann
2014-06-16 18:53 ` Stuart Yoder
2014-06-17 10:26 ` Varun Sethi
2014-06-17 10:43 ` Will Deacon
2014-06-17 11:21 ` Varun Sethi
2014-06-17 14:50 ` Stuart Yoder
2014-06-18 9:29 ` Will Deacon
2014-06-17 14:39 ` Stuart Yoder
2014-06-20 23:16 ` Olav Haugan
2014-06-24 9:18 ` Will Deacon
2014-06-24 17:57 ` Olav Haugan
2014-06-24 18:11 ` Will Deacon
2014-06-24 18:20 ` Arnd Bergmann
2014-06-25 9:17 ` Will Deacon
2014-06-25 9:27 ` Arnd Bergmann
2014-06-25 9:38 ` Will Deacon
2014-06-25 9:48 ` Arnd Bergmann
2014-06-25 9:57 ` Will Deacon
2014-06-25 10:12 ` Arnd Bergmann
2014-06-25 10:14 ` Will Deacon
2014-06-24 21:35 ` Olav Haugan
2014-06-25 9:18 ` Will Deacon
2014-06-27 22:23 ` Olav Haugan
2014-06-30 9:52 ` Will Deacon
2014-07-09 1:07 ` Olav Haugan
2014-07-09 10:54 ` Will Deacon
2014-07-10 22:32 ` Olav Haugan
2014-07-11 12:24 ` Will Deacon
[not found] <20140606224542.GA22188@mithrandir>
2014-06-07 13:22 ` Arnd Bergmann
2014-06-09 10:49 ` Thierry Reding
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