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    SubjectRE: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes required by fsl PAMU driver.
    Date


    > -----Original Message-----
    > From: Wood Scott-B07421
    > Sent: Monday, December 03, 2012 10:34 PM
    > To: Sethi Varun-B16395
    > Cc: Joerg Roedel; linux-kernel@vger.kernel.org; iommu@lists.linux-
    > foundation.org; Wood Scott-B07421; linuxppc-dev@lists.ozlabs.org; Tabi
    > Timur-B04825
    > Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes
    > required by fsl PAMU driver.
    >
    > On 12/03/2012 10:57:29 AM, Sethi Varun-B16395 wrote:
    > >
    > >
    > > > -----Original Message-----
    > > > From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
    > > > bounces@lists.linux-foundation.org] On Behalf Of Joerg Roedel
    > > > Sent: Sunday, December 02, 2012 7:33 PM
    > > > To: Sethi Varun-B16395
    > > > Cc: linux-kernel@vger.kernel.org; iommu@lists.linux-foundation.org;
    > > Wood
    > > > Scott-B07421; linuxppc-dev@lists.ozlabs.org; Tabi Timur-B04825
    > > > Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes
    > > > required by fsl PAMU driver.
    > > >
    > > > Hmm, we need to work out a good abstraction for this.
    > > >
    > > > On Tue, Nov 20, 2012 at 07:24:56PM +0530, Varun Sethi wrote:
    > > > > Added the following domain attributes required by FSL PAMU driver:
    > > > > 1. Subwindows field added to the iommu domain geometry attribute.
    > > >
    > > > Are the Subwindows mapped with full size or do you map only parts
    > > of the
    > > > subwindows?
    > > >
    > > [Sethi Varun-B16395] It's possible to map a part of the subwindow i.e.
    > > size of the mapping can be less than the sub window size.
    > >
    > > > > + * This attribute indicates number of DMA subwindows
    > supported
    > > by
    > > > > + * the geometry. If there is a single window that maps the
    > > entire
    > > > > + * geometry, attribute must be set to "1". A value of "0"
    > > implies
    > > > > + * that this mechanism is not used at all(normal paging is
    > > used).
    > > > > + * Value other than* "0" or "1" indicates the actual number
    > of
    > > > > + * subwindows.
    > > > > + */
    > > >
    > > > This semantic is ugly, how about a feature detection mechanism?
    > > >
    > > [Sethi Varun-B16395] A feature mechanism to query the type of IOMMU?
    >
    > A feature mechanism to determine whether this subwindow mechanism is
    > available, and what the limits are.
    >
    So, we use the IOMMU capability interface to find out if IOMMU supports sub windows or not, right? But still number of sub windows would be specified as a part of the geometry and the valid value for sub windows would 0,1 or actual number of sub windows.

    -Varun




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