From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v6 8/8] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops
Date: Thu, 15 Jan 2015 11:12:17 +0000 [thread overview]
Message-ID: <20150115111211.GF23475@arm.com> (raw)
In-Reply-To: <20150115082843.GB30799@ulmo>
On Thu, Jan 15, 2015 at 08:28:44AM +0000, Thierry Reding wrote:
> On Wed, Jan 14, 2015 at 10:46:10AM +0000, Will Deacon wrote:
> > On Wed, Jan 14, 2015 at 09:00:24AM +0000, Alexandre Courbot wrote:
> [...]
> > > 2) Say you want to use the IOMMU API in your driver, and have an iommu
> > > property in your device's DT node. If by chance your IOMMU is registered
> > > early, you will already have a mapping automatically created even before
> > > your probe function is called. Can this be avoided? Is it even safe?
> >
> > Currently, I think you have to either teardown the ops manually or return
> > an error from of_xlate. Thierry was also looking at this sort of thing,
> > so it might be worth talking to him.
>
> I already explained in earlier threads why I think this is a bad idea.
> It's completely unnatural for any driver to manually tear down something
> that it didn't want set up in the first place. It also means that you
> have to carefully audit any users of these IOMMU APIs to make sure that
> they do tear down. That doesn't sound like a good incremental approach,
> as evidenced by the breakage that Alex and Heiko have encountered.
Well, perhaps we hide that behind a get_iommu API or something. We *do*
need this manual teardown step to support things like VFIO, so it makes
sense to reuse it for other users too imo.
> The solution for me has been to completely side-step the issue and not
> register the IOMMU with the new mechanism at all. That is, there's no
> .of_xlate() implementation, which means that the ARM DMA API glue won't
> try to be smart and use the IOMMU in ways it's not meant to be used.
> This has several advantages, such as that I can also use the regular
> driver model for suspend/resume of the IOMMU, and I get to enjoy the
> benefits of devres in the IOMMU driver. Probe ordering is still a tiny
> issue, but we can easily solve that using explicit initcall ordering
> (which really isn't any worse than IOMMU_OF_DECLARE()).
That's a pity. I'd much rather extend what we currently have to satisfy
your use-case. Ho-hum.
Will
next prev parent reply other threads:[~2015-01-15 11:12 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-01 16:57 [PATCH v6 0/8] Introduce automatic DMA configuration for IOMMU masters Will Deacon
2014-12-01 16:57 ` [PATCH v6 1/8] iommu: provide early initialisation hook for IOMMU drivers Will Deacon
2014-12-01 23:54 ` Rob Herring
2014-12-02 9:23 ` Marek Szyprowski
2014-12-02 9:36 ` Arnd Bergmann
2014-12-02 9:43 ` Will Deacon
2014-12-02 12:05 ` Thierry Reding
2014-12-02 10:30 ` Pantelis Antoniou
2014-12-02 14:16 ` Grant Likely
2014-12-03 19:57 ` Arnd Bergmann
2014-12-04 9:49 ` Will Deacon
2014-12-04 10:10 ` Arnd Bergmann
2014-12-04 10:21 ` Will Deacon
2014-12-04 11:19 ` Arnd Bergmann
2014-12-04 11:25 ` Grant Likely
2014-12-04 11:52 ` Will Deacon
2014-12-04 12:43 ` Grant Likely
2014-12-04 12:26 ` Robin Murphy
2014-12-04 12:42 ` Grant Likely
2014-12-04 13:43 ` Robin Murphy
2014-12-04 13:58 ` Grant Likely
2014-12-04 14:49 ` Thierry Reding
2014-12-04 17:42 ` Robin Murphy
2014-12-04 17:58 ` Grant Likely
2014-12-04 19:42 ` Robin Murphy
2014-12-05 12:10 ` Will Deacon
2014-12-05 12:21 ` Arnd Bergmann
2014-12-05 12:35 ` Robin Murphy
2014-12-05 13:06 ` Grant Likely
2014-12-05 13:18 ` Thierry Reding
2014-12-05 13:21 ` Grant Likely
2014-12-05 13:31 ` Thierry Reding
2014-12-05 13:49 ` Marek Szyprowski
2014-12-04 12:51 ` Arnd Bergmann
2014-12-01 16:57 ` [PATCH v6 2/8] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops Will Deacon
2014-12-01 22:58 ` Rob Herring
2014-12-02 9:16 ` Arnd Bergmann
2014-12-01 16:57 ` [PATCH v6 3/8] iommu: add new iommu_ops callback for adding an OF device Will Deacon
2014-12-01 16:57 ` [PATCH v6 4/8] iommu: provide helper function to configure an IOMMU for an of master Will Deacon
2014-12-01 16:57 ` [PATCH v6 5/8] iommu: fix initialization without 'add_device' callback Will Deacon
2014-12-01 16:57 ` [PATCH v6 6/8] dma-mapping: detect and configure IOMMU in of_dma_configure Will Deacon
2014-12-01 23:06 ` Rob Herring
2014-12-10 14:52 ` Rob Clark
2014-12-10 15:08 ` Will Deacon
2014-12-10 15:54 ` Robin Murphy
2014-12-10 15:56 ` Laurent Pinchart
2014-12-14 15:49 ` Laurent Pinchart
2014-12-14 15:59 ` Laurent Pinchart
2014-12-15 17:10 ` Will Deacon
2014-12-15 16:40 ` Will Deacon
2014-12-15 17:16 ` Laurent Pinchart
2014-12-15 18:09 ` Will Deacon
2014-12-16 12:08 ` Arnd Bergmann
2014-12-17 12:09 ` Will Deacon
2014-12-17 14:15 ` Arnd Bergmann
2014-12-17 14:45 ` Will Deacon
2014-12-17 15:35 ` Arnd Bergmann
2014-12-17 17:17 ` Will Deacon
2014-12-17 19:48 ` Arnd Bergmann
2014-12-21 10:04 ` Will Deacon
2014-12-22 13:36 ` Arnd Bergmann
2015-01-07 18:57 ` Will Deacon
2015-01-07 19:29 ` Arnd Bergmann
2015-01-08 10:53 ` Will Deacon
2014-12-17 14:27 ` Robin Murphy
2014-12-17 15:01 ` Will Deacon
2014-12-17 15:38 ` Arnd Bergmann
2014-12-17 17:20 ` Will Deacon
2014-12-17 0:05 ` Laurent Pinchart
2014-12-14 15:51 ` Laurent Pinchart
2014-12-15 11:32 ` Will Deacon
2014-12-17 0:19 ` Laurent Pinchart
2014-12-17 11:14 ` Will Deacon
2014-12-01 16:57 ` [PATCH v6 7/8] arm: call iommu_init before of_platform_populate Will Deacon
2014-12-01 16:57 ` [PATCH v6 8/8] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops Will Deacon
2015-01-14 9:00 ` Alexandre Courbot
2015-01-14 10:46 ` Will Deacon
2015-01-14 13:51 ` Heiko Stübner
2015-01-14 19:17 ` Will Deacon
2015-01-15 8:30 ` Thierry Reding
2015-01-15 11:13 ` Will Deacon
2015-01-15 2:57 ` Alexandre Courbot
2015-01-15 8:28 ` Thierry Reding
2015-01-15 11:12 ` Will Deacon [this message]
2015-01-15 23:18 ` Laurent Pinchart
2015-01-18 6:54 ` Alexandre Courbot
2015-01-18 11:18 ` Laurent Pinchart
2015-01-19 11:12 ` Will Deacon
2015-01-19 11:34 ` Laurent Pinchart
2015-01-19 12:31 ` Thierry Reding
2015-01-20 15:14 ` Laurent Pinchart
2015-01-20 15:19 ` Will Deacon
2015-01-20 15:21 ` Will Deacon
2015-01-20 15:35 ` Laurent Pinchart
2015-01-19 12:43 ` Thierry Reding
2015-01-19 12:50 ` Will Deacon
2015-01-19 13:36 ` Thierry Reding
2015-01-20 13:50 ` Laurent Pinchart
2015-01-19 16:13 ` Arnd Bergmann
2015-01-20 16:41 ` Laurent Pinchart
2015-01-19 12:36 ` Thierry Reding
2015-01-19 15:52 ` Arnd Bergmann
2015-01-19 16:21 ` Thierry Reding
2015-01-19 17:02 ` Arnd Bergmann
2015-01-20 13:47 ` Laurent Pinchart
2015-01-19 12:49 ` Thierry Reding
2015-01-20 14:05 ` Laurent Pinchart
2014-12-05 7:12 ` [PATCH v6 0/8] Introduce automatic DMA configuration for IOMMU masters Olof Johansson
2014-12-05 12:11 ` Will Deacon
2014-12-15 0:24 ` [PATCH/RFC] iommu/ipmmu-vmsa: Use DT-based instantiation Laurent Pinchart
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