arm: dma-mapping: Add support to extend DMA IOMMU mappings

Instead of using just one bitmap to keep track of IO virtual addresses
(handed out for IOMMU use) introduce an array of bitmaps. This allows
us to extend existing mappings when running out of iova space in the
initial mapping etc.

If there is not enough space in the mapping to service an IO virtual
address allocation request, __alloc_iova() tries to extend the mapping
-- by allocating another bitmap -- and makes another allocation
attempt using the freshly allocated bitmap.

This allows arm iommu drivers to start with a decent initial size when
an dma_iommu_mapping is created and still to avoid running out of IO
virtual addresses for the mapping.

Signed-off-by: Andreas Herrmann <andreas.herrmann@calxeda.com>
[mszyprow: removed extensions parameter to arm_iommu_create_mapping()
 function, which will be modified in the next patch anyway, also some
 debug messages about extending bitmap]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h
index a8c56acc8c985ba54b917f08c2956f3d26a1cca1..686797cf5618776c717e7c14e691f010f35dce4b 100644 (file)
--- a/arch/arm/include/asm/dma-iommu.h
+++ b/arch/arm/include/asm/dma-iommu.h
@@ -13,8 +13,12 @@ struct dma_iommu_mapping {
        /* iommu specific data */
        struct iommu_domain     *domain;
 
-       void                    *bitmap;
-       size_t                  bits;
+       unsigned long           **bitmaps;      /* array of bitmaps */
+       unsigned int            nr_bitmaps;     /* nr of elements in array */
+       unsigned int            extensions;
+       size_t                  bitmap_size;    /* size of a single bitmap */
+       size_t                  bits;           /* per bitmap */
+       unsigned int            size;           /* per bitmap */
        unsigned int            order;
        dma_addr_t              base;
 

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 11b3914660d2a9f518f15b09028d3dad78ad07e0..4d06295b8e3ef1ef3067f4faa0417e78bb688aff 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1069,6 +1069,8 @@ fs_initcall(dma_debug_do_init);
 
 /* IOMMU */
 
+static int extend_iommu_mapping(struct dma_iommu_mapping *mapping);
+
 static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
                                      size_t size)
 {
@@ -1076,6 +1078,8 @@ static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
        unsigned int align = 0;
        unsigned int count, start;
        unsigned long flags;
+       dma_addr_t iova;
+       int i;
 
        if (order > CONFIG_ARM_DMA_IOMMU_ALIGNMENT)
                order = CONFIG_ARM_DMA_IOMMU_ALIGNMENT;
@@ -1087,30 +1091,78 @@ static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
                align = (1 << (order - mapping->order)) - 1;
 
        spin_lock_irqsave(&mapping->lock, flags);
-       start = bitmap_find_next_zero_area(mapping->bitmap, mapping->bits, 0,
-                                          count, align);
-       if (start > mapping->bits) {
-               spin_unlock_irqrestore(&mapping->lock, flags);
-               return DMA_ERROR_CODE;
+       for (i = 0; i < mapping->nr_bitmaps; i++) {
+               start = bitmap_find_next_zero_area(mapping->bitmaps[i],
+                               mapping->bits, 0, count, align);
+
+               if (start > mapping->bits)
+                       continue;
+
+               bitmap_set(mapping->bitmaps[i], start, count);
+               break;
        }
 
-       bitmap_set(mapping->bitmap, start, count);
+       /*
+        * No unused range found. Try to extend the existing mapping
+        * and perform a second attempt to reserve an IO virtual
+        * address range of size bytes.
+        */
+       if (i == mapping->nr_bitmaps) {
+               if (extend_iommu_mapping(mapping)) {
+                       spin_unlock_irqrestore(&mapping->lock, flags);
+                       return DMA_ERROR_CODE;
+               }
+
+               start = bitmap_find_next_zero_area(mapping->bitmaps[i],
+                               mapping->bits, 0, count, align);
+
+               if (start > mapping->bits) {
+                       spin_unlock_irqrestore(&mapping->lock, flags);
+                       return DMA_ERROR_CODE;
+               }
+
+               bitmap_set(mapping->bitmaps[i], start, count);
+       }
        spin_unlock_irqrestore(&mapping->lock, flags);
 
-       return mapping->base + (start << (mapping->order + PAGE_SHIFT));
+       iova = mapping->base + (mapping->size * i);
+       iova += start << (mapping->order + PAGE_SHIFT);
+
+       return iova;
 }
 
 static inline void __free_iova(struct dma_iommu_mapping *mapping,
                               dma_addr_t addr, size_t size)
 {
-       unsigned int start = (addr - mapping->base) >>
-                            (mapping->order + PAGE_SHIFT);
-       unsigned int count = ((size >> PAGE_SHIFT) +
-                             (1 << mapping->order) - 1) >> mapping->order;
+       unsigned int start, count;
        unsigned long flags;
+       dma_addr_t bitmap_base;
+       u32 bitmap_index;
+
+       if (!size)
+               return;
+
+       bitmap_index = (u32) (addr - mapping->base) / (u32) mapping->size;
+       BUG_ON(addr < mapping->base || bitmap_index > mapping->extensions);
+
+       bitmap_base = mapping->base + mapping->size * bitmap_index;
+
+       start = (addr - bitmap_base) >> (mapping->order + PAGE_SHIFT);
+
+       if (addr + size > bitmap_base + mapping->size) {
+               /*
+                * The address range to be freed reaches into the iova
+                * range of the next bitmap. This should not happen as
+                * we don't allow this in __alloc_iova (at the
+                * moment).
+                */
+               BUG();
+       } else
+               count = ((size >> PAGE_SHIFT) +
+                       (1 << mapping->order) - 1) >> mapping->order;
 
        spin_lock_irqsave(&mapping->lock, flags);
-       bitmap_clear(mapping->bitmap, start, count);
+       bitmap_clear(mapping->bitmaps[bitmap_index], start, count);
        spin_unlock_irqrestore(&mapping->lock, flags);
 }
 
@@ -1890,8 +1942,8 @@ arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
                         int order)
 {
        unsigned int count = size >> (PAGE_SHIFT + order);
-       unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);
        struct dma_iommu_mapping *mapping;
+       int extensions = 0;
        int err = -ENOMEM;
 
        if (!count)
@@ -1901,23 +1953,35 @@ arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
        if (!mapping)
                goto err;
 
-       mapping->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
-       if (!mapping->bitmap)
+       mapping->bitmap_size = BITS_TO_LONGS(count) * sizeof(long);
+       mapping->bitmaps = kzalloc((extensions + 1) * sizeof(unsigned long *),
+                               GFP_KERNEL);
+       if (!mapping->bitmaps)
                goto err2;
 
+       mapping->bitmaps[0] = kzalloc(mapping->bitmap_size, GFP_KERNEL);
+       if (!mapping->bitmaps[0])
+               goto err3;
+
+       mapping->nr_bitmaps = 1;
+       mapping->extensions = extensions;
        mapping->base = base;
-       mapping->bits = BITS_PER_BYTE * bitmap_size;
+       mapping->size = size;
        mapping->order = order;
+       mapping->bits = BITS_PER_BYTE * mapping->bitmap_size;
+
        spin_lock_init(&mapping->lock);
 
        mapping->domain = iommu_domain_alloc(bus);
        if (!mapping->domain)
-               goto err3;
+               goto err4;
 
        kref_init(&mapping->kref);
        return mapping;
+err4:
+       kfree(mapping->bitmaps[0]);
 err3:
-       kfree(mapping->bitmap);
+       kfree(mapping->bitmaps);
 err2:
        kfree(mapping);
 err:
@@ -1927,14 +1991,35 @@ EXPORT_SYMBOL_GPL(arm_iommu_create_mapping);
 
 static void release_iommu_mapping(struct kref *kref)
 {
+       int i;
        struct dma_iommu_mapping *mapping =
                container_of(kref, struct dma_iommu_mapping, kref);
 
        iommu_domain_free(mapping->domain);
-       kfree(mapping->bitmap);
+       for (i = 0; i < mapping->nr_bitmaps; i++)
+               kfree(mapping->bitmaps[i]);
+       kfree(mapping->bitmaps);
        kfree(mapping);
 }
 
+static int extend_iommu_mapping(struct dma_iommu_mapping *mapping)
+{
+       int next_bitmap;
+
+       if (mapping->nr_bitmaps > mapping->extensions)
+               return -EINVAL;
+
+       next_bitmap = mapping->nr_bitmaps;
+       mapping->bitmaps[next_bitmap] = kzalloc(mapping->bitmap_size,
+                                               GFP_ATOMIC);
+       if (!mapping->bitmaps[next_bitmap])
+               return -ENOMEM;
+
+       mapping->nr_bitmaps++;
+
+       return 0;
+}
+
 void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping)
 {
        if (mapping)