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SubjectRe: [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?

> + * 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?

> +struct iommu_stash_attribute {
> + u32 cpu; /* cpu number */
> + u32 cache; /* cache to stash to: L1,L2,L3 */
> };
>
> struct iommu_domain {
> @@ -60,6 +95,14 @@ struct iommu_domain {
> enum iommu_attr {
> DOMAIN_ATTR_MAX,
> DOMAIN_ATTR_GEOMETRY,
> + /* Set the IOMMU hardware stashing
> + * parameters.
> + */
> + DOMAIN_ATTR_STASH,
> + /* Explicity enable/disable DMA for a
> + * particular memory window.
> + */
> + DOMAIN_ATTR_ENABLE,
> };

When you add implementation specific attributes please add some
indication to the names that it is only for PAMU. DOMAIN_ATTR_STASH
sounds too generic.


Joerg




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