Messages in this thread | | | Date | Mon, 5 Nov 2012 17:56:07 -0600 | From | Scott Wood <> | Subject | Re: [PATCH 3/4 v4] iommu/fsl: Add iommu domain attributes required by fsl PAMU driver. |
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On 11/05/2012 05:19:20 AM, Varun Sethi wrote: > Added the following domain attributes required by FSL PAMU driver: > 1. Subwindows field added to the iommu domain geometry attribute. > 2. Added new iommu stash attribute, which allows setting of the > LIODN specific stash id parameter through IOMMU API. > 3. Added an attribute for enabling/disabling DMA to a particular > memory window. > > > Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com> > --- > changes in v4: > - Updated comment explaining subwindows(as mentioned by Scott). > change in v3: > -renamed the stash attribute targets > include/linux/iommu.h | 36 ++++++++++++++++++++++++++++++++++++ > 1 files changed, 36 insertions(+), 0 deletions(-) > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index f3b99e1..e72f5e5 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -44,6 +44,34 @@ struct iommu_domain_geometry { > dma_addr_t aperture_start; /* First address that can be > mapped */ > dma_addr_t aperture_end; /* Last address that can be > mapped */ > bool force_aperture; /* DMA only allowed in mappable > range? */ > + > + /** > + * There could be a single contiguous window tha maps the entire > + * geometry or it could be split in to multiple subwindows.
...or it could be a normal IOMMU that supports arbitrary paging throughout the aperture.
> + * Subwindows allow for supporting physically discontiguous > mappings.
...in the absence of arbitrary paging.
> + * This attribute indicates number of DMA subwindows supported > by > + * the geometry.
s/indicates number/indicates the number/
> If there is a single window that maps the entire > + * geometry, attribute must be set to "1". A value of "0" > implies > + * that there are 256 subwindows each of size 4K. Value other > than > + * "0" or "1" indicates the actual number of subwindows.
No, a value of "0" indicates that this mechanism is not in use at all, and normal paging is used. PAMU specific things like "256 subwindows" must not be a default value in a generic API.
In the case of PAMU, if you specify 0 here, the aperture is limited to 1 MiB because that is the limit of PAMU's ability to simulate arbitrary paging with subwindows, but this is only the limit of one implementation. It's not part of the API.
-Scott
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