[PATCH] swiotlb: move from arch/ia64/lib/ to lib/

The swiotlb implementation is shared by both IA-64 and EM64T. However,
the source itself lives under arch/ia64. This patch moves swiotlb.c
from arch/ia64/lib to lib/ and fixes-up the appropriate Makefile and
Kconfig files. No actual changes are made to swiotlb.c.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 759 insertions, 0 deletions

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
new file mode 100644
index 000000000000..875b0c16250c
--- /dev/null
+++ b/lib/swiotlb.c
@@ -0,0 +1,759 @@
+/*
+ * Dynamic DMA mapping support.
+ *
+ * This implementation is for IA-64 platforms that do not support
+ * I/O TLBs (aka DMA address translation hardware).
+ * Copyright (C) 2000 Asit Mallick <Asit.K.Mallick@intel.com>
+ * Copyright (C) 2000 Goutham Rao <goutham.rao@intel.com>
+ * Copyright (C) 2000, 2003 Hewlett-Packard Co
+ *      David Mosberger-Tang <davidm@hpl.hp.com>
+ *
+ * 03/05/07 davidm      Switch from PCI-DMA to generic device DMA API.
+ * 00/12/13 davidm      Rename to swiotlb.c and add mark_clean() to avoid
+ *                      unnecessary i-cache flushing.
+ * 04/07/.. ak          Better overflow handling. Assorted fixes.
+ */
+
+#include <linux/cache.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ctype.h>
+
+#include <asm/io.h>
+#include <asm/pci.h>
+#include <asm/dma.h>
+
+#include <linux/init.h>
+#include <linux/bootmem.h>
+
+#define OFFSET(val,align) ((unsigned long)      \
+                           ( (val) & ( (align) - 1)))
+
+#define SG_ENT_VIRT_ADDRESS(sg) (page_address((sg)->page) + (sg)->offset)
+#define SG_ENT_PHYS_ADDRESS(SG) virt_to_phys(SG_ENT_VIRT_ADDRESS(SG))
+
+/*
+ * Maximum allowable number of contiguous slabs to map,
+ * must be a power of 2.  What is the appropriate value ?
+ * The complexity of {map,unmap}_single is linearly dependent on this value.
+ */
+#define IO_TLB_SEGSIZE  128
+
+/*
+ * log of the size of each IO TLB slab.  The number of slabs is command line
+ * controllable.
+ */
+#define IO_TLB_SHIFT 11
+
+#define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
+
+/*
+ * Minimum IO TLB size to bother booting with.  Systems with mainly
+ * 64bit capable cards will only lightly use the swiotlb.  If we can't
+ * allocate a contiguous 1MB, we're probably in trouble anyway.
+ */
+#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
+
+int swiotlb_force;
+
+/*
+ * Used to do a quick range check in swiotlb_unmap_single and
+ * swiotlb_sync_single_*, to see if the memory was in fact allocated by this
+ * API.
+ */
+static char *io_tlb_start, *io_tlb_end;
+
+/*
+ * The number of IO TLB blocks (in groups of 64) betweeen io_tlb_start and
+ * io_tlb_end.  This is command line adjustable via setup_io_tlb_npages.
+ */
+static unsigned long io_tlb_nslabs;
+
+/*
+ * When the IOMMU overflows we return a fallback buffer. This sets the size.
+ */
+static unsigned long io_tlb_overflow = 32*1024;
+
+void *io_tlb_overflow_buffer;
+
+/*
+ * This is a free list describing the number of free entries available from
+ * each index
+ */
+static unsigned int *io_tlb_list;
+static unsigned int io_tlb_index;
+
+/*
+ * We need to save away the original address corresponding to a mapped entry
+ * for the sync operations.
+ */
+static unsigned char **io_tlb_orig_addr;
+
+/*
+ * Protect the above data structures in the map and unmap calls
+ */
+static DEFINE_SPINLOCK(io_tlb_lock);
+
+static int __init
+setup_io_tlb_npages(char *str)
+{
+        if (isdigit(*str)) {
+                io_tlb_nslabs = simple_strtoul(str, &str, 0);
+                /* avoid tail segment of size < IO_TLB_SEGSIZE */
+                io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+        }
+        if (*str == ',')
+                ++str;
+        if (!strcmp(str, "force"))
+                swiotlb_force = 1;
+        return 1;
+}
+__setup("swiotlb=", setup_io_tlb_npages);
+/* make io_tlb_overflow tunable too? */
+
+/*
+ * Statically reserve bounce buffer space and initialize bounce buffer data
+ * structures for the software IO TLB used to implement the PCI DMA API.
+ */
+void
+swiotlb_init_with_default_size (size_t default_size)
+{
+        unsigned long i;
+
+        if (!io_tlb_nslabs) {
+                io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
+                io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+        }
+
+        /*
+         * Get IO TLB memory from the low pages
+         */
+        io_tlb_start = alloc_bootmem_low_pages(io_tlb_nslabs *
+                                               (1 << IO_TLB_SHIFT));
+        if (!io_tlb_start)
+                panic("Cannot allocate SWIOTLB buffer");
+        io_tlb_end = io_tlb_start + io_tlb_nslabs * (1 << IO_TLB_SHIFT);
+
+        /*
+         * Allocate and initialize the free list array.  This array is used
+         * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
+         * between io_tlb_start and io_tlb_end.
+         */
+        io_tlb_list = alloc_bootmem(io_tlb_nslabs * sizeof(int));
+        for (i = 0; i < io_tlb_nslabs; i++)
+                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+        io_tlb_index = 0;
+        io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(char *));
+
+        /*
+         * Get the overflow emergency buffer
+         */
+        io_tlb_overflow_buffer = alloc_bootmem_low(io_tlb_overflow);
+        printk(KERN_INFO "Placing software IO TLB between 0x%lx - 0x%lx\n",
+               virt_to_phys(io_tlb_start), virt_to_phys(io_tlb_end));
+}
+
+void
+swiotlb_init (void)
+{
+        swiotlb_init_with_default_size(64 * (1<<20));   /* default to 64MB */
+}
+
+/*
+ * Systems with larger DMA zones (those that don't support ISA) can
+ * initialize the swiotlb later using the slab allocator if needed.
+ * This should be just like above, but with some error catching.
+ */
+int
+swiotlb_late_init_with_default_size (size_t default_size)
+{
+        unsigned long i, req_nslabs = io_tlb_nslabs;
+        unsigned int order;
+
+        if (!io_tlb_nslabs) {
+                io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
+                io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+        }
+
+        /*
+         * Get IO TLB memory from the low pages
+         */
+        order = get_order(io_tlb_nslabs * (1 << IO_TLB_SHIFT));
+        io_tlb_nslabs = SLABS_PER_PAGE << order;
+
+        while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
+                io_tlb_start = (char *)__get_free_pages(GFP_DMA | __GFP_NOWARN,
+                                                        order);
+                if (io_tlb_start)
+                        break;
+                order--;
+        }
+
+        if (!io_tlb_start)
+                goto cleanup1;
+
+        if (order != get_order(io_tlb_nslabs * (1 << IO_TLB_SHIFT))) {
+                printk(KERN_WARNING "Warning: only able to allocate %ld MB "
+                       "for software IO TLB\n", (PAGE_SIZE << order) >> 20);
+                io_tlb_nslabs = SLABS_PER_PAGE << order;
+        }
+        io_tlb_end = io_tlb_start + io_tlb_nslabs * (1 << IO_TLB_SHIFT);
+        memset(io_tlb_start, 0, io_tlb_nslabs * (1 << IO_TLB_SHIFT));
+
+        /*
+         * Allocate and initialize the free list array.  This array is used
+         * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
+         * between io_tlb_start and io_tlb_end.
+         */
+        io_tlb_list = (unsigned int *)__get_free_pages(GFP_KERNEL,
+                                      get_order(io_tlb_nslabs * sizeof(int)));
+        if (!io_tlb_list)
+                goto cleanup2;
+
+        for (i = 0; i < io_tlb_nslabs; i++)
+                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+        io_tlb_index = 0;
+
+        io_tlb_orig_addr = (unsigned char **)__get_free_pages(GFP_KERNEL,
+                                   get_order(io_tlb_nslabs * sizeof(char *)));
+        if (!io_tlb_orig_addr)
+                goto cleanup3;
+
+        memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(char *));
+
+        /*
+         * Get the overflow emergency buffer
+         */
+        io_tlb_overflow_buffer = (void *)__get_free_pages(GFP_DMA,
+                                                  get_order(io_tlb_overflow));
+        if (!io_tlb_overflow_buffer)
+                goto cleanup4;
+
+        printk(KERN_INFO "Placing %ldMB software IO TLB between 0x%lx - "
+               "0x%lx\n", (io_tlb_nslabs * (1 << IO_TLB_SHIFT)) >> 20,
+               virt_to_phys(io_tlb_start), virt_to_phys(io_tlb_end));
+
+        return 0;
+
+cleanup4:
+        free_pages((unsigned long)io_tlb_orig_addr, get_order(io_tlb_nslabs *
+                                                              sizeof(char *)));
+        io_tlb_orig_addr = NULL;
+cleanup3:
+        free_pages((unsigned long)io_tlb_list, get_order(io_tlb_nslabs *
+                                                         sizeof(int)));
+        io_tlb_list = NULL;
+        io_tlb_end = NULL;
+cleanup2:
+        free_pages((unsigned long)io_tlb_start, order);
+        io_tlb_start = NULL;
+cleanup1:
+        io_tlb_nslabs = req_nslabs;
+        return -ENOMEM;
+}
+
+static inline int
+address_needs_mapping(struct device *hwdev, dma_addr_t addr)
+{
+        dma_addr_t mask = 0xffffffff;
+        /* If the device has a mask, use it, otherwise default to 32 bits */
+        if (hwdev && hwdev->dma_mask)
+                mask = *hwdev->dma_mask;
+        return (addr & ~mask) != 0;
+}
+
+/*
+ * Allocates bounce buffer and returns its kernel virtual address.
+ */
+static void *
+map_single(struct device *hwdev, char *buffer, size_t size, int dir)
+{
+        unsigned long flags;
+        char *dma_addr;
+        unsigned int nslots, stride, index, wrap;
+        int i;
+
+        /*
+         * For mappings greater than a page, we limit the stride (and
+         * hence alignment) to a page size.
+         */
+        nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+        if (size > PAGE_SIZE)
+                stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
+        else
+                stride = 1;
+
+        if (!nslots)
+                BUG();
+
+        /*
+         * Find suitable number of IO TLB entries size that will fit this
+         * request and allocate a buffer from that IO TLB pool.
+         */
+        spin_lock_irqsave(&io_tlb_lock, flags);
+        {
+                wrap = index = ALIGN(io_tlb_index, stride);
+
+                if (index >= io_tlb_nslabs)
+                        wrap = index = 0;
+
+                do {
+                        /*
+                         * If we find a slot that indicates we have 'nslots'
+                         * number of contiguous buffers, we allocate the
+                         * buffers from that slot and mark the entries as '0'
+                         * indicating unavailable.
+                         */
+                        if (io_tlb_list[index] >= nslots) {
+                                int count = 0;
+
+                                for (i = index; i < (int) (index + nslots); i++)
+                                        io_tlb_list[i] = 0;
+                                for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
+                                        io_tlb_list[i] = ++count;
+                                dma_addr = io_tlb_start + (index << IO_TLB_SHIFT);
+
+                                /*
+                                 * Update the indices to avoid searching in
+                                 * the next round.
+                                 */
+                                io_tlb_index = ((index + nslots) < io_tlb_nslabs
+                                                ? (index + nslots) : 0);
+
+                                goto found;
+                        }
+                        index += stride;
+                        if (index >= io_tlb_nslabs)
+                                index = 0;
+                } while (index != wrap);
+
+                spin_unlock_irqrestore(&io_tlb_lock, flags);
+                return NULL;
+        }
+  found:
+        spin_unlock_irqrestore(&io_tlb_lock, flags);
+
+        /*
+         * Save away the mapping from the original address to the DMA address.
+         * This is needed when we sync the memory.  Then we sync the buffer if
+         * needed.
+         */
+        io_tlb_orig_addr[index] = buffer;
+        if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
+                memcpy(dma_addr, buffer, size);
+
+        return dma_addr;
+}
+
+/*
+ * dma_addr is the kernel virtual address of the bounce buffer to unmap.
+ */
+static void
+unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
+{
+        unsigned long flags;
+        int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+        int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
+        char *buffer = io_tlb_orig_addr[index];
+
+        /*
+         * First, sync the memory before unmapping the entry
+         */
+        if (buffer && ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
+                /*
+                 * bounce... copy the data back into the original buffer * and
+                 * delete the bounce buffer.
+                 */
+                memcpy(buffer, dma_addr, size);
+
+        /*
+         * Return the buffer to the free list by setting the corresponding
+         * entries to indicate the number of contigous entries available.
+         * While returning the entries to the free list, we merge the entries
+         * with slots below and above the pool being returned.
+         */
+        spin_lock_irqsave(&io_tlb_lock, flags);
+        {
+                count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ?
+                         io_tlb_list[index + nslots] : 0);
+                /*
+                 * Step 1: return the slots to the free list, merging the
+                 * slots with superceeding slots
+                 */
+                for (i = index + nslots - 1; i >= index; i--)
+                        io_tlb_list[i] = ++count;
+                /*
+                 * Step 2: merge the returned slots with the preceding slots,
+                 * if available (non zero)
+                 */
+                for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
+                        io_tlb_list[i] = ++count;
+        }
+        spin_unlock_irqrestore(&io_tlb_lock, flags);
+}
+
+static void
+sync_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
+{
+        int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
+        char *buffer = io_tlb_orig_addr[index];
+
+        /*
+         * bounce... copy the data back into/from the original buffer
+         * XXX How do you handle DMA_BIDIRECTIONAL here ?
+         */
+        if (dir == DMA_FROM_DEVICE)
+                memcpy(buffer, dma_addr, size);
+        else if (dir == DMA_TO_DEVICE)
+                memcpy(dma_addr, buffer, size);
+        else
+                BUG();
+}
+
+void *
+swiotlb_alloc_coherent(struct device *hwdev, size_t size,
+                       dma_addr_t *dma_handle, int flags)
+{
+        unsigned long dev_addr;
+        void *ret;
+        int order = get_order(size);
+
+        /*
+         * XXX fix me: the DMA API should pass us an explicit DMA mask
+         * instead, or use ZONE_DMA32 (ia64 overloads ZONE_DMA to be a ~32
+         * bit range instead of a 16MB one).
+         */
+        flags |= GFP_DMA;
+
+        ret = (void *)__get_free_pages(flags, order);
+        if (ret && address_needs_mapping(hwdev, virt_to_phys(ret))) {
+                /*
+                 * The allocated memory isn't reachable by the device.
+                 * Fall back on swiotlb_map_single().
+                 */
+                free_pages((unsigned long) ret, order);
+                ret = NULL;
+        }
+        if (!ret) {
+                /*
+                 * We are either out of memory or the device can't DMA
+                 * to GFP_DMA memory; fall back on
+                 * swiotlb_map_single(), which will grab memory from
+                 * the lowest available address range.
+                 */
+                dma_addr_t handle;
+                handle = swiotlb_map_single(NULL, NULL, size, DMA_FROM_DEVICE);
+                if (dma_mapping_error(handle))
+                        return NULL;
+
+                ret = phys_to_virt(handle);
+        }
+
+        memset(ret, 0, size);
+        dev_addr = virt_to_phys(ret);
+
+        /* Confirm address can be DMA'd by device */
+        if (address_needs_mapping(hwdev, dev_addr)) {
+                printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016lx\n",
+                       (unsigned long long)*hwdev->dma_mask, dev_addr);
+                panic("swiotlb_alloc_coherent: allocated memory is out of "
+                      "range for device");
+        }
+        *dma_handle = dev_addr;
+        return ret;
+}
+
+void
+swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
+                      dma_addr_t dma_handle)
+{
+        if (!(vaddr >= (void *)io_tlb_start
+                    && vaddr < (void *)io_tlb_end))
+                free_pages((unsigned long) vaddr, get_order(size));
+        else
+                /* DMA_TO_DEVICE to avoid memcpy in unmap_single */
+                swiotlb_unmap_single (hwdev, dma_handle, size, DMA_TO_DEVICE);
+}
+
+static void
+swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
+{
+        /*
+         * Ran out of IOMMU space for this operation. This is very bad.
+         * Unfortunately the drivers cannot handle this operation properly.
+         * unless they check for pci_dma_mapping_error (most don't)
+         * When the mapping is small enough return a static buffer to limit
+         * the damage, or panic when the transfer is too big.
+         */
+        printk(KERN_ERR "PCI-DMA: Out of SW-IOMMU space for %lu bytes at "
+               "device %s\n", size, dev ? dev->bus_id : "?");
+
+        if (size > io_tlb_overflow && do_panic) {
+                if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)
+                        panic("PCI-DMA: Memory would be corrupted\n");
+                if (dir == PCI_DMA_TODEVICE || dir == PCI_DMA_BIDIRECTIONAL)
+                        panic("PCI-DMA: Random memory would be DMAed\n");
+        }
+}
+
+/*
+ * Map a single buffer of the indicated size for DMA in streaming mode.  The
+ * PCI address to use is returned.
+ *
+ * Once the device is given the dma address, the device owns this memory until
+ * either swiotlb_unmap_single or swiotlb_dma_sync_single is performed.
+ */
+dma_addr_t
+swiotlb_map_single(struct device *hwdev, void *ptr, size_t size, int dir)
+{
+        unsigned long dev_addr = virt_to_phys(ptr);
+        void *map;
+
+        if (dir == DMA_NONE)
+                BUG();
+        /*
+         * If the pointer passed in happens to be in the device's DMA window,
+         * we can safely return the device addr and not worry about bounce
+         * buffering it.
+         */
+        if (!address_needs_mapping(hwdev, dev_addr) && !swiotlb_force)
+                return dev_addr;
+
+        /*
+         * Oh well, have to allocate and map a bounce buffer.
+         */
+        map = map_single(hwdev, ptr, size, dir);
+        if (!map) {
+                swiotlb_full(hwdev, size, dir, 1);
+                map = io_tlb_overflow_buffer;
+        }
+
+        dev_addr = virt_to_phys(map);
+
+        /*
+         * Ensure that the address returned is DMA'ble
+         */
+        if (address_needs_mapping(hwdev, dev_addr))
+                panic("map_single: bounce buffer is not DMA'ble");
+
+        return dev_addr;
+}
+
+/*
+ * Since DMA is i-cache coherent, any (complete) pages that were written via
+ * DMA can be marked as "clean" so that lazy_mmu_prot_update() doesn't have to
+ * flush them when they get mapped into an executable vm-area.
+ */
+static void
+mark_clean(void *addr, size_t size)
+{
+        unsigned long pg_addr, end;
+
+        pg_addr = PAGE_ALIGN((unsigned long) addr);
+        end = (unsigned long) addr + size;
+        while (pg_addr + PAGE_SIZE <= end) {
+                struct page *page = virt_to_page(pg_addr);
+                set_bit(PG_arch_1, &page->flags);
+                pg_addr += PAGE_SIZE;
+        }
+}
+
+/*
+ * Unmap a single streaming mode DMA translation.  The dma_addr and size must
+ * match what was provided for in a previous swiotlb_map_single call.  All
+ * other usages are undefined.
+ *
+ * After this call, reads by the cpu to the buffer are guaranteed to see
+ * whatever the device wrote there.
+ */
+void
+swiotlb_unmap_single(struct device *hwdev, dma_addr_t dev_addr, size_t size,
+                     int dir)
+{
+        char *dma_addr = phys_to_virt(dev_addr);
+
+        if (dir == DMA_NONE)
+                BUG();
+        if (dma_addr >= io_tlb_start && dma_addr < io_tlb_end)
+                unmap_single(hwdev, dma_addr, size, dir);
+        else if (dir == DMA_FROM_DEVICE)
+                mark_clean(dma_addr, size);
+}
+
+/*
+ * Make physical memory consistent for a single streaming mode DMA translation
+ * after a transfer.
+ *
+ * If you perform a swiotlb_map_single() but wish to interrogate the buffer
+ * using the cpu, yet do not wish to teardown the PCI dma mapping, you must
+ * call this function before doing so.  At the next point you give the PCI dma
+ * address back to the card, you must first perform a
+ * swiotlb_dma_sync_for_device, and then the device again owns the buffer
+ */
+void
+swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
+                            size_t size, int dir)
+{
+        char *dma_addr = phys_to_virt(dev_addr);
+
+        if (dir == DMA_NONE)
+                BUG();
+        if (dma_addr >= io_tlb_start && dma_addr < io_tlb_end)
+                sync_single(hwdev, dma_addr, size, dir);
+        else if (dir == DMA_FROM_DEVICE)
+                mark_clean(dma_addr, size);
+}
+
+void
+swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
+                               size_t size, int dir)
+{
+        char *dma_addr = phys_to_virt(dev_addr);
+
+        if (dir == DMA_NONE)
+                BUG();
+        if (dma_addr >= io_tlb_start && dma_addr < io_tlb_end)
+                sync_single(hwdev, dma_addr, size, dir);
+        else if (dir == DMA_FROM_DEVICE)
+                mark_clean(dma_addr, size);
+}
+
+/*
+ * Map a set of buffers described by scatterlist in streaming mode for DMA.
+ * This is the scatter-gather version of the above swiotlb_map_single
+ * interface.  Here the scatter gather list elements are each tagged with the
+ * appropriate dma address and length.  They are obtained via
+ * sg_dma_{address,length}(SG).
+ *
+ * NOTE: An implementation may be able to use a smaller number of
+ *       DMA address/length pairs than there are SG table elements.
+ *       (for example via virtual mapping capabilities)
+ *       The routine returns the number of addr/length pairs actually
+ *       used, at most nents.
+ *
+ * Device ownership issues as mentioned above for swiotlb_map_single are the
+ * same here.
+ */
+int
+swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+               int dir)
+{
+        void *addr;
+        unsigned long dev_addr;
+        int i;
+
+        if (dir == DMA_NONE)
+                BUG();
+
+        for (i = 0; i < nelems; i++, sg++) {
+                addr = SG_ENT_VIRT_ADDRESS(sg);
+                dev_addr = virt_to_phys(addr);
+                if (swiotlb_force || address_needs_mapping(hwdev, dev_addr)) {
+                        sg->dma_address = (dma_addr_t) virt_to_phys(map_single(hwdev, addr, sg->length, dir));
+                        if (!sg->dma_address) {
+                                /* Don't panic here, we expect map_sg users
+                                   to do proper error handling. */
+                                swiotlb_full(hwdev, sg->length, dir, 0);
+                                swiotlb_unmap_sg(hwdev, sg - i, i, dir);
+                                sg[0].dma_length = 0;
+                                return 0;
+                        }
+                } else
+                        sg->dma_address = dev_addr;
+                sg->dma_length = sg->length;
+        }
+        return nelems;
+}
+
+/*
+ * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
+ * concerning calls here are the same as for swiotlb_unmap_single() above.
+ */
+void
+swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+                 int dir)
+{
+        int i;
+
+        if (dir == DMA_NONE)
+                BUG();
+
+        for (i = 0; i < nelems; i++, sg++)
+                if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
+                        unmap_single(hwdev, (void *) phys_to_virt(sg->dma_address), sg->dma_length, dir);
+                else if (dir == DMA_FROM_DEVICE)
+                        mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
+}
+
+/*
+ * Make physical memory consistent for a set of streaming mode DMA translations
+ * after a transfer.
+ *
+ * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
+ * and usage.
+ */
+void
+swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
+                        int nelems, int dir)
+{
+        int i;
+
+        if (dir == DMA_NONE)
+                BUG();
+
+        for (i = 0; i < nelems; i++, sg++)
+                if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
+                        sync_single(hwdev, (void *) sg->dma_address,
+                                    sg->dma_length, dir);
+}
+
+void
+swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+                           int nelems, int dir)
+{
+        int i;
+
+        if (dir == DMA_NONE)
+                BUG();
+
+        for (i = 0; i < nelems; i++, sg++)
+                if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
+                        sync_single(hwdev, (void *) sg->dma_address,
+                                    sg->dma_length, dir);
+}
+
+int
+swiotlb_dma_mapping_error(dma_addr_t dma_addr)
+{
+        return (dma_addr == virt_to_phys(io_tlb_overflow_buffer));
+}
+
+/*
+ * Return whether the given PCI device DMA address mask can be supported
+ * properly.  For example, if your device can only drive the low 24-bits
+ * during PCI bus mastering, then you would pass 0x00ffffff as the mask to
+ * this function.
+ */
+int
+swiotlb_dma_supported (struct device *hwdev, u64 mask)
+{
+        return (virt_to_phys (io_tlb_end) - 1) <= mask;
+}
+
+EXPORT_SYMBOL(swiotlb_init);
+EXPORT_SYMBOL(swiotlb_map_single);
+EXPORT_SYMBOL(swiotlb_unmap_single);
+EXPORT_SYMBOL(swiotlb_map_sg);
+EXPORT_SYMBOL(swiotlb_unmap_sg);
+EXPORT_SYMBOL(swiotlb_sync_single_for_cpu);
+EXPORT_SYMBOL(swiotlb_sync_single_for_device);
+EXPORT_SYMBOL(swiotlb_sync_sg_for_cpu);
+EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
+EXPORT_SYMBOL(swiotlb_dma_mapping_error);
+EXPORT_SYMBOL(swiotlb_alloc_coherent);
+EXPORT_SYMBOL(swiotlb_free_coherent);
+EXPORT_SYMBOL(swiotlb_dma_supported);