From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2] devicetree: Add generic IOMMU device tree bindings
Date: Tue, 24 Jun 2014 19:11:50 +0100 [thread overview]
Message-ID: <20140624181150.GB4067@arm.com> (raw)
In-Reply-To: <53A9BC18.2090106@codeaurora.org>
On Tue, Jun 24, 2014 at 06:57:44PM +0100, Olav Haugan wrote:
> On 6/24/2014 2:18 AM, Will Deacon wrote:
> > On Sat, Jun 21, 2014 at 12:16:25AM +0100, Olav Haugan wrote:
> >> We have multiple-master SMMUs and each master emits a variable number of
> >> StreamIDs. However, we have to apply a mask (the ARM SMMU spec allows
> >> for this) to the StreamIDs due to limited number of StreamID 2 Context
> >> Bank entries in the SMMU. If my understanding is correct we would
> >> represent this in the DT like this:
> >>
> >> iommu {
> >> #address-cells = <2>;
> >> #size-cells = <0>;
> >> };
> >>
> >> master at a {
> >> ...
> >> iommus = <&iommu StreamID0 MASK0>,
> >> <&iommu StreamID1 MASK1>,
> >> <&iommu StreamID2 MASK2>;
> >> };
> >
> > Stupid question, but why not simply describe the masked IDs? What use does
> > the `raw' ID have to Linux?
>
> We do describe the masked StreamID (SID) but we need to specify the mask
> that the SMMU should apply to the incoming SIDs, right?
>
> We have a bus master that emits 43 unique SIDs. However, we have only 40
> SMMU_SMRn registers in the SMMU. So we need to mask out some of the
> incoming SID bits so that the 43 SIDs can match one of 40 entries in the
> SMR.
Hmm, so you're talking about stream matching, right? That doesn't belong in
the device-tree. I appreciate that the current driver does a terrible job at
allocating the SMRs (it's bloody difficult!), but we should try to improve
the dynamic behaviour instead of moving configuration of the SMMU out into
device-tree, where it's inflexible at best.
There have been patches previously posted by Andreas Herrmann helping here.
I'd be glad to see them revived.
Will
next prev parent reply other threads:[~2014-06-24 18:11 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1400877218-4113-1-git-send-email-thierry.reding@gmail.com>
2014-05-30 13:16 ` [PATCH v2] devicetree: Add generic IOMMU device tree bindings 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 [this message]
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
2014-05-23 20:36 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
2014-06-02 11:44 ` Dave Martin
2014-06-04 21:32 ` Thierry Reding
2014-06-05 9:42 ` Arnd Bergmann
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