iommu/iova: Support disabling domain iova alignment

Currently the IOVA framework automatically applies IOVA alignment to
provided IOVAs based on the requested IOVA size and the alignment configs
which are enabled.

Some clients who don't require any IOVA alignment would benefit from the
reduced fragmentation that would result from disabling IOVA alignment.

Add support to allow clients to disable IOVA alignment on an IOMMU domain.

Change-Id: Ifa6a75576e7a084c443abf38726d790b883f00b3
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
[lmark@codeaurora.org: cleanup change]
Signed-off-by: Liam Mark <lmark@codeaurora.org>

drivers/iommu/Kconfig

@@ -35,6 +35,22 @@ config IOMMU_IOVA_ALIGNMENT
 	  The order is expressed a power of two multiplied by the PAGE_SIZE.
 
 	  If unsure, leave the default value "9".
+
+config DMA_CONFIGURE_ALIGNMENT
+        bool "Configure IOVA alignment"
+        help
+	  Currently the IOVA framework automatically applies IOVA
+	  alignment to provided IOVAs based on the requested IOVA size and
+	  the alignment configs which are enabled.
+
+	  Some clients who don't require any IOVA alignment would
+	  benefit from the reduced fragmentation that would result from
+	  disabling IOVA alignment.
+
+	  Enable this option to allow clients to disable IOVA alignment on
+	  an IOMMU domain.
+
+	  If unsure, say N.
 endif
 
 menuconfig IOMMU_SUPPORT

drivers/iommu/dma-iommu.c

@@ -400,6 +400,27 @@ int iommu_dma_enable_best_fit_algo(struct device *dev)
 }
 EXPORT_SYMBOL(iommu_dma_enable_best_fit_algo);
 
+#ifdef CONFIG_DMA_CONFIGURE_ALIGNMENT
+/*
+ * Should be called prior to using dma-apis.
+ */
+int iommu_dma_configure_alignment(struct device *dev, bool force_no_align)
+{
+	struct iommu_domain *domain;
+	struct iova_domain *iovad;
+
+	domain = iommu_get_domain_for_dev(dev);
+	if (!domain || !domain->iova_cookie)
+		return -EINVAL;
+
+	iovad = &((struct iommu_dma_cookie *)domain->iova_cookie)->iovad;
+
+	iovad->force_no_align = force_no_align;
+	return 0;
+}
+EXPORT_SYMBOL(iommu_dma_configure_alignment);
+#endif
+
 /**
  * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
  *                    page flags.

drivers/iommu/iova.c

@@ -51,6 +51,9 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	rb_link_node(&iovad->anchor.node, NULL, &iovad->rbroot.rb_node);
 	rb_insert_color(&iovad->anchor.node, &iovad->rbroot);
 	iovad->best_fit = false;
+#ifdef CONFIG_DMA_CONFIGURE_ALIGNMENT
+	iovad->force_no_align = false;
+#endif
 	init_iova_rcaches(iovad);
 }
 EXPORT_SYMBOL_GPL(init_iova_domain);
@@ -385,6 +388,11 @@ alloc_iova(struct iova_domain *iovad, unsigned long size,
 	if (!new_iova)
 		return NULL;
 
+#ifdef CONFIG_DMA_CONFIGURE_ALIGNMENT
+	if (iovad->force_no_align)
+		size_aligned = false;
+#endif
+
 	if (iovad->best_fit) {
 		ret = __alloc_and_insert_iova_best_fit(iovad, size,
 				limit_pfn + 1, new_iova, size_aligned);

include/linux/dma-iommu.h

@@ -58,6 +58,16 @@ int iommu_dma_reserve_iova(struct device *dev, dma_addr_t base,
 
 int iommu_dma_enable_best_fit_algo(struct device *dev);
 
+#ifdef CONFIG_DMA_CONFIGURE_ALIGNMENT
+int iommu_dma_configure_alignment(struct device *dev, bool force_no_align);
+#else /* CONFIG_DMA_CONFIGURE_ALIGNMENT */
+static inline int iommu_dma_configure_alignment(struct device *dev,
+						bool force_no_align)
+{
+	return -ENOTSUPP;
+}
+#endif
+
 #else /* CONFIG_IOMMU_DMA */
 
 struct iommu_domain;
@@ -110,5 +120,11 @@ static inline int iommu_dma_enable_best_fit_algo(struct device *dev)
 	return -ENODEV;
 }
 
+static inline int iommu_dma_configure_alignment(struct device *dev,
+						bool force_no_align)
+{
+	return -ENODEV;
+}
+
 #endif	/* CONFIG_IOMMU_DMA */
 #endif	/* __DMA_IOMMU_H */

include/linux/iova.h

@@ -96,6 +96,9 @@ struct iova_domain {
 	atomic_t fq_timer_on;			/* 1 when timer is active, 0
 						   when not */
 	bool best_fit;
+#ifdef CONFIG_DMA_CONFIGURE_ALIGNMENT
+	bool force_no_align;
+#endif
 };
 
 static inline unsigned long iova_size(struct iova *iova)