From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH v4 0/8] Introduce automatic DMA configuration for IOMMU masters
Date: Fri, 14 Nov 2014 19:27:54 +0000 [thread overview]
Message-ID: <20141114192754.GB9291@arm.com> (raw)
In-Reply-To: <3630936.HRExZgJGyp@wuerfel>
Hi Arnd,
Thanks for having a look.
On Fri, Nov 14, 2014 at 07:11:23PM +0000, Arnd Bergmann wrote:
> On Friday 14 November 2014 18:56:29 Will Deacon wrote:
> >
> > Here is the fourth iteration of the RFC I've previously posted here:
> >
> > RFCv1: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-August/283023.html
> > RFCv2: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-September/283752.html
> > RFCv3: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-September/287031.html
> >
> > Changes since RFCv3 include:
> >
> > - Drastic simplification of the data structures, so that we no longer
> > pass around lists of domains. Instead, dma-mapping is expected to
> > allocate the domain (Joerg talked about adding a get_default_domain
> > operation to iommu_ops).
> >
> > - iommu_ops is used to hold the per-instance IOMMU data
> >
> > - Configuration of DMA segments added to of_dma_configure
> >
> > All feedback welcome.
> >
> >
>
> Overall I think this is really nice, and I don't mind this going in,
> I only have one issue with they way you use iommu_ops now:
Hehe, I thought you might have something to say about that. I also had second
thoughts, but decided it wasn't worse than what we already have (more below).
> At the moment, iommu_ops is a structure that can get used for any
> number of iommus of the same type, but by putting per-device private
> data into the same structure you have to duplicate it per instance.
I'm not sure I agree -- the pgsize_bitmap, for example, could vary between
different implementations of the same IOMMU. I think we already have this in
Juno (some SMMUs can only do 64k pages, whilst others can do 4k and 64k).
> I think rather than adding a .priv pointer to iommu_ops, we should do
> the same thing that a lot of other subsystems have:
>
> /* generic structure */
> struct iommu {
> struct iommu_ops *ops;
> /* possibly other generic per-instance members */
> };
>
> /* driver specific structure */
> struct arm_smmu {
> struct iommu iommu;
>
> /* smmu specific members */
> };
> static inline struct arm_smmu *to_arm_smmu(struct iommu *iommu)
> {
> return container_of(iommu, struct arm_smmu, iommu);
> }
Regardless of the arguments above, I think this layout is cleaner. We could
also move the pgsize_bitmap into struct iommu in that case, however, that
would be a more invasive patch series than I what I currently have.
If I do another version of the patch, I can easily add a struct iommu and
stash that in the device_node data for the IOMMU instead of directly
putting the ops there. That's at least a step in the right direction.
Cheers,
Will
next prev parent reply other threads:[~2014-11-14 19:27 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-14 18:56 [RFC PATCH v4 0/8] Introduce automatic DMA configuration for IOMMU masters Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 1/8] iommu: provide early initialisation hook for IOMMU drivers Will Deacon
2014-11-18 12:28 ` Marek Szyprowski
2014-11-14 18:56 ` [RFC PATCH v4 2/8] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 3/8] iommu: add new iommu_ops callback for adding an OF device Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 4/8] iommu: provide helper function to configure an IOMMU for an of master Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 5/8] dma-mapping: detect and configure IOMMU in of_dma_configure Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 6/8] dma-mapping: set dma segment properties " Will Deacon
2014-11-25 13:05 ` Robin Murphy
2014-11-26 11:37 ` Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 7/8] arm: call iommu_init before of_platform_populate Will Deacon
2014-11-14 18:56 ` [RFC PATCH v4 8/8] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops Will Deacon
2014-11-17 11:29 ` Robin Murphy
2014-11-17 11:41 ` Will Deacon
2014-11-14 19:11 ` [RFC PATCH v4 0/8] Introduce automatic DMA configuration for IOMMU masters Arnd Bergmann
2014-11-14 19:27 ` Will Deacon [this message]
2014-11-14 20:01 ` Arnd Bergmann
2015-01-19 16:06 ` Will Deacon
2015-01-20 16:56 ` Laurent Pinchart
2015-01-21 14:48 ` Will Deacon
2015-01-21 15:02 ` Laurent Pinchart
2014-11-19 11:21 ` Marek Szyprowski
2014-11-19 11:41 ` Will Deacon
2014-11-25 7:35 ` Marek Szyprowski
2014-11-26 17:47 ` Will Deacon
2014-11-28 13:03 ` jroedel at suse.de
2014-11-28 13:19 ` Will Deacon
2014-12-15 17:21 ` Laurent Pinchart
2014-12-15 17:34 ` Will Deacon
2014-12-15 17:55 ` Laurent Pinchart
2014-11-25 13:15 ` Robin Murphy
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