/*
 * Copyright (C) 2001 Mike Corrigan & Dave Engebretsen, IBM Corporation
 * 
 * Rewrite, cleanup, new allocation schemes, virtual merging: 
 * Copyright (C) 2004 Olof Johansson, IBM Corporation
 *               and  Ben. Herrenschmidt, IBM Corporation
 *
 * Dynamic DMA mapping support, bus-independent parts.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */


#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/dma-mapping.h>
#include <linux/bitmap.h>
#include <linux/iommu-helper.h>
#include <linux/crash_dump.h>
#include <linux/hash.h>
#include <linux/fault-inject.h>
#include <linux/pci.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/iommu.h>
#include <asm/pci-bridge.h>
#include <asm/machdep.h>
#include <asm/kdump.h>
#include <asm/fadump.h>
#include <asm/vio.h>

#define DBG(...)

static int novmerge;

static void __iommu_free(struct iommu_table *, dma_addr_t, unsigned int);

static int __init setup_iommu(char *str)
{
        if (!strcmp(str, "novmerge"))
                novmerge = 1;
        else if (!strcmp(str, "vmerge"))
                novmerge = 0;
        return 1;
}

__setup("iommu=", setup_iommu);

static DEFINE_PER_CPU(unsigned int, iommu_pool_hash);

/*
 * We precalculate the hash to avoid doing it on every allocation.
 *
 * The hash is important to spread CPUs across all the pools. For example,
 * on a POWER7 with 4 way SMT we want interrupts on the primary threads and
 * with 4 pools all primary threads would map to the same pool.
 */
static int __init setup_iommu_pool_hash(void)
{
        unsigned int i;

        for_each_possible_cpu(i)
                per_cpu(iommu_pool_hash, i) = hash_32(i, IOMMU_POOL_HASHBITS);

        return 0;
}
subsys_initcall(setup_iommu_pool_hash);

#ifdef CONFIG_FAIL_IOMMU

static DECLARE_FAULT_ATTR(fail_iommu);

static int __init setup_fail_iommu(char *str)
{
        return setup_fault_attr(&fail_iommu, str);
}
__setup("fail_iommu=", setup_fail_iommu);

static bool should_fail_iommu(struct device *dev)
{
        return dev->archdata.fail_iommu && should_fail(&fail_iommu, 1);
}

static int __init fail_iommu_debugfs(void)
{
        struct dentry *dir = fault_create_debugfs_attr("fail_iommu",
                                                       NULL, &fail_iommu);

        return IS_ERR(dir) ? PTR_ERR(dir) : 0;
}
late_initcall(fail_iommu_debugfs);

static ssize_t fail_iommu_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", dev->archdata.fail_iommu);
}

static ssize_t fail_iommu_store(struct device *dev,
                                struct device_attribute *attr, const char *buf,
                                size_t count)
{
        int i;

        if (count > 0 && sscanf(buf, "%d", &i) > 0)
                dev->archdata.fail_iommu = (i == 0) ? 0 : 1;

        return count;
}

static DEVICE_ATTR(fail_iommu, S_IRUGO|S_IWUSR, fail_iommu_show,
                   fail_iommu_store);

static int fail_iommu_bus_notify(struct notifier_block *nb,
                                 unsigned long action, void *data)
{
        struct device *dev = data;

        if (action == BUS_NOTIFY_ADD_DEVICE) {
                if (device_create_file(dev, &dev_attr_fail_iommu))
                        pr_warn("Unable to create IOMMU fault injection sysfs "
                                "entries\n");
        } else if (action == BUS_NOTIFY_DEL_DEVICE) {
                device_remove_file(dev, &dev_attr_fail_iommu);
        }

        return 0;
}

static struct notifier_block fail_iommu_bus_notifier = {
        .notifier_call = fail_iommu_bus_notify
};

static int __init fail_iommu_setup(void)
{
#ifdef CONFIG_PCI
        bus_register_notifier(&pci_bus_type, &fail_iommu_bus_notifier);
#endif
#ifdef CONFIG_IBMVIO
        bus_register_notifier(&vio_bus_type, &fail_iommu_bus_notifier);
#endif

        return 0;
}
/*
 * Must execute after PCI and VIO subsystem have initialised but before
 * devices are probed.
 */
arch_initcall(fail_iommu_setup);
#else
static inline bool should_fail_iommu(struct device *dev)
{
        return false;
}
#endif

static unsigned long iommu_range_alloc(struct device *dev,
                                       struct iommu_table *tbl,
                                       unsigned long npages,
                                       unsigned long *handle,
                                       unsigned long mask,
                                       unsigned int align_order)
{ 
        unsigned long n, end, start;
        unsigned long limit;
        int largealloc = npages > 15;
        int pass = 0;
        unsigned long align_mask;
        unsigned long boundary_size;
        unsigned long flags;
        unsigned int pool_nr;
        struct iommu_pool *pool;

        align_mask = 0xffffffffffffffffl >> (64 - align_order);

        /* This allocator was derived from x86_64's bit string search */

        /* Sanity check */
        if (unlikely(npages == 0)) {
                if (printk_ratelimit())
                        WARN_ON(1);
                return DMA_ERROR_CODE;
        }

        if (should_fail_iommu(dev))
                return DMA_ERROR_CODE;

        /*
         * We don't need to disable preemption here because any CPU can
         * safely use any IOMMU pool.
         */
        pool_nr = __raw_get_cpu_var(iommu_pool_hash) & (tbl->nr_pools - 1);

        if (largealloc)
                pool = &(tbl->large_pool);
        else
                pool = &(tbl->pools[pool_nr]);

        spin_lock_irqsave(&(pool->lock), flags);

again:
        if ((pass == 0) && handle && *handle &&
            (*handle >= pool->start) && (*handle < pool->end))
                start = *handle;
        else
                start = pool->hint;

        limit = pool->end;

        /* The case below can happen if we have a small segment appended
         * to a large, or when the previous alloc was at the very end of
         * the available space. If so, go back to the initial start.
         */
        if (start >= limit)
                start = pool->start;

        if (limit + tbl->it_offset > mask) {
                limit = mask - tbl->it_offset + 1;
                /* If we're constrained on address range, first try
                 * at the masked hint to avoid O(n) search complexity,
                 * but on second pass, start at 0 in pool 0.
                 */
                if ((start & mask) >= limit || pass > 0) {
                        spin_unlock(&(pool->lock));
                        pool = &(tbl->pools[0]);
                        spin_lock(&(pool->lock));
                        start = pool->start;
                } else {
                        start &= mask;
                }
        }

        if (dev)
                boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1,
                                      1 << IOMMU_PAGE_SHIFT);
        else
                boundary_size = ALIGN(1UL << 32, 1 << IOMMU_PAGE_SHIFT);
        /* 4GB boundary for iseries_hv_alloc and iseries_hv_map */

        n = iommu_area_alloc(tbl->it_map, limit, start, npages,
                             tbl->it_offset, boundary_size >> IOMMU_PAGE_SHIFT,
                             align_mask);
        if (n == -1) {
                if (likely(pass == 0)) {
                        /* First try the pool from the start */
                        pool->hint = pool->start;
                        pass++;
                        goto again;

                } else if (pass <= tbl->nr_pools) {
                        /* Now try scanning all the other pools */
                        spin_unlock(&(pool->lock));
                        pool_nr = (pool_nr + 1) & (tbl->nr_pools - 1);
                        pool = &tbl->pools[pool_nr];
                        spin_lock(&(pool->lock));
                        pool->hint = pool->start;
                        pass++;
                        goto again;

                } else {
                        /* Give up */
                        spin_unlock_irqrestore(&(pool->lock), flags);
                        return DMA_ERROR_CODE;
                }
        }

        end = n + npages;

        /* Bump the hint to a new block for small allocs. */
        if (largealloc) {
                /* Don't bump to new block to avoid fragmentation */
                pool->hint = end;
        } else {
                /* Overflow will be taken care of at the next allocation */
                pool->hint = (end + tbl->it_blocksize - 1) &
                                ~(tbl->it_blocksize - 1);
        }

        /* Update handle for SG allocations */
        if (handle)
                *handle = end;

        spin_unlock_irqrestore(&(pool->lock), flags);

        return n;
}

static dma_addr_t iommu_alloc(struct device *dev, struct iommu_table *tbl,
                              void *page, unsigned int npages,
                              enum dma_data_direction direction,
                              unsigned long mask, unsigned int align_order,
                              struct dma_attrs *attrs)
{
        unsigned long entry;
        dma_addr_t ret = DMA_ERROR_CODE;
        int build_fail;

        entry = iommu_range_alloc(dev, tbl, npages, NULL, mask, align_order);

        if (unlikely(entry == DMA_ERROR_CODE))
                return DMA_ERROR_CODE;

        entry += tbl->it_offset;        /* Offset into real TCE table */
        ret = entry << IOMMU_PAGE_SHIFT;        /* Set the return dma address */

        /* Put the TCEs in the HW table */
        build_fail = ppc_md.tce_build(tbl, entry, npages,
                                      (unsigned long)page & IOMMU_PAGE_MASK,
                                      direction, attrs);

        /* ppc_md.tce_build() only returns non-zero for transient errors.
         * Clean up the table bitmap in this case and return
         * DMA_ERROR_CODE. For all other errors the functionality is
         * not altered.
         */
        if (unlikely(build_fail)) {
                __iommu_free(tbl, ret, npages);
                return DMA_ERROR_CODE;
        }

        /* Flush/invalidate TLB caches if necessary */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        /* Make sure updates are seen by hardware */
        mb();

        return ret;
}

static bool iommu_free_check(struct iommu_table *tbl, dma_addr_t dma_addr,
                             unsigned int npages)
{
        unsigned long entry, free_entry;

        entry = dma_addr >> IOMMU_PAGE_SHIFT;
        free_entry = entry - tbl->it_offset;

        if (((free_entry + npages) > tbl->it_size) ||
            (entry < tbl->it_offset)) {
                if (printk_ratelimit()) {
                        printk(KERN_INFO "iommu_free: invalid entry\n");
                        printk(KERN_INFO "\tentry     = 0x%lx\n", entry); 
                        printk(KERN_INFO "\tdma_addr  = 0x%llx\n", (u64)dma_addr);
                        printk(KERN_INFO "\tTable     = 0x%llx\n", (u64)tbl);
                        printk(KERN_INFO "\tbus#      = 0x%llx\n", (u64)tbl->it_busno);
                        printk(KERN_INFO "\tsize      = 0x%llx\n", (u64)tbl->it_size);
                        printk(KERN_INFO "\tstartOff  = 0x%llx\n", (u64)tbl->it_offset);
                        printk(KERN_INFO "\tindex     = 0x%llx\n", (u64)tbl->it_index);
                        WARN_ON(1);
                }

                return false;
        }

        return true;
}

static struct iommu_pool *get_pool(struct iommu_table *tbl,
                                   unsigned long entry)
{
        struct iommu_pool *p;
        unsigned long largepool_start = tbl->large_pool.start;

        /* The large pool is the last pool at the top of the table */
        if (entry >= largepool_start) {
                p = &tbl->large_pool;
        } else {
                unsigned int pool_nr = entry / tbl->poolsize;

                BUG_ON(pool_nr > tbl->nr_pools);
                p = &tbl->pools[pool_nr];
        }

        return p;
}

static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
                         unsigned int npages)
{
        unsigned long entry, free_entry;
        unsigned long flags;
        struct iommu_pool *pool;

        entry = dma_addr >> IOMMU_PAGE_SHIFT;
        free_entry = entry - tbl->it_offset;

        pool = get_pool(tbl, free_entry);

        if (!iommu_free_check(tbl, dma_addr, npages))
                return;

        ppc_md.tce_free(tbl, entry, npages);

        spin_lock_irqsave(&(pool->lock), flags);
        bitmap_clear(tbl->it_map, free_entry, npages);
        spin_unlock_irqrestore(&(pool->lock), flags);
}

static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
                unsigned int npages)
{
        __iommu_free(tbl, dma_addr, npages);

        /* Make sure TLB cache is flushed if the HW needs it. We do
         * not do an mb() here on purpose, it is not needed on any of
         * the current platforms.
         */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);
}

int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
                 struct scatterlist *sglist, int nelems,
                 unsigned long mask, enum dma_data_direction direction,
                 struct dma_attrs *attrs)
{
        dma_addr_t dma_next = 0, dma_addr;
        struct scatterlist *s, *outs, *segstart;
        int outcount, incount, i, build_fail = 0;
        unsigned int align;
        unsigned long handle;
        unsigned int max_seg_size;

        BUG_ON(direction == DMA_NONE);

        if ((nelems == 0) || !tbl)
                return 0;

        outs = s = segstart = &sglist[0];
        outcount = 1;
        incount = nelems;
        handle = 0;

        /* Init first segment length for backout at failure */
        outs->dma_length = 0;

        DBG("sg mapping %d elements:\n", nelems);

        max_seg_size = dma_get_max_seg_size(dev);
        for_each_sg(sglist, s, nelems, i) {
                unsigned long vaddr, npages, entry, slen;

                slen = s->length;
                /* Sanity check */
                if (slen == 0) {
                        dma_next = 0;
                        continue;
                }
                /* Allocate iommu entries for that segment */
                vaddr = (unsigned long) sg_virt(s);
                npages = iommu_num_pages(vaddr, slen, IOMMU_PAGE_SIZE);
                align = 0;
                if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && slen >= PAGE_SIZE &&
                    (vaddr & ~PAGE_MASK) == 0)
                        align = PAGE_SHIFT - IOMMU_PAGE_SHIFT;
                entry = iommu_range_alloc(dev, tbl, npages, &handle,
                                          mask >> IOMMU_PAGE_SHIFT, align);

                DBG("  - vaddr: %lx, size: %lx\n", vaddr, slen);

                /* Handle failure */
                if (unlikely(entry == DMA_ERROR_CODE)) {
                        if (printk_ratelimit())
                                dev_info(dev, "iommu_alloc failed, tbl %p "
                                         "vaddr %lx npages %lu\n", tbl, vaddr,
                                         npages);
                        goto failure;
                }

                /* Convert entry to a dma_addr_t */
                entry += tbl->it_offset;
                dma_addr = entry << IOMMU_PAGE_SHIFT;
                dma_addr |= (s->offset & ~IOMMU_PAGE_MASK);

                DBG("  - %lu pages, entry: %lx, dma_addr: %lx\n",
                            npages, entry, dma_addr);

                /* Insert into HW table */
                build_fail = ppc_md.tce_build(tbl, entry, npages,
                                              vaddr & IOMMU_PAGE_MASK,
                                              direction, attrs);
                if(unlikely(build_fail))
                        goto failure;

                /* If we are in an open segment, try merging */
                if (segstart != s) {
                        DBG("  - trying merge...\n");
                        /* We cannot merge if:
                         * - allocated dma_addr isn't contiguous to previous allocation
                         */
                        if (novmerge || (dma_addr != dma_next) ||
                            (outs->dma_length + s->length > max_seg_size)) {
                                /* Can't merge: create a new segment */
                                segstart = s;
                                outcount++;
                                outs = sg_next(outs);
                                DBG("    can't merge, new segment.\n");
                        } else {
                                outs->dma_length += s->length;
                                DBG("    merged, new len: %ux\n", outs->dma_length);
                        }
                }

                if (segstart == s) {
                        /* This is a new segment, fill entries */
                        DBG("  - filling new segment.\n");
                        outs->dma_address = dma_addr;
                        outs->dma_length = slen;
                }

                /* Calculate next page pointer for contiguous check */
                dma_next = dma_addr + slen;

                DBG("  - dma next is: %lx\n", dma_next);
        }

        /* Flush/invalidate TLB caches if necessary */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        DBG("mapped %d elements:\n", outcount);

        /* For the sake of iommu_unmap_sg, we clear out the length in the
         * next entry of the sglist if we didn't fill the list completely
         */
        if (outcount < incount) {
                outs = sg_next(outs);
                outs->dma_address = DMA_ERROR_CODE;
                outs->dma_length = 0;
        }

        /* Make sure updates are seen by hardware */
        mb();

        return outcount;

 failure:
        for_each_sg(sglist, s, nelems, i) {
                if (s->dma_length != 0) {
                        unsigned long vaddr, npages;

                        vaddr = s->dma_address & IOMMU_PAGE_MASK;
                        npages = iommu_num_pages(s->dma_address, s->dma_length,
                                                 IOMMU_PAGE_SIZE);
                        __iommu_free(tbl, vaddr, npages);
                        s->dma_address = DMA_ERROR_CODE;
                        s->dma_length = 0;
                }
                if (s == outs)
                        break;
        }
        return 0;
}


void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist,
                int nelems, enum dma_data_direction direction,
                struct dma_attrs *attrs)
{
        struct scatterlist *sg;

        BUG_ON(direction == DMA_NONE);

        if (!tbl)
                return;

        sg = sglist;
        while (nelems--) {
                unsigned int npages;
                dma_addr_t dma_handle = sg->dma_address;

                if (sg->dma_length == 0)
                        break;
                npages = iommu_num_pages(dma_handle, sg->dma_length,
                                         IOMMU_PAGE_SIZE);
                __iommu_free(tbl, dma_handle, npages);
                sg = sg_next(sg);
        }

        /* Flush/invalidate TLBs if necessary. As for iommu_free(), we
         * do not do an mb() here, the affected platforms do not need it
         * when freeing.
         */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);
}

static void iommu_table_clear(struct iommu_table *tbl)
{
        /*
         * In case of firmware assisted dump system goes through clean
         * reboot process at the time of system crash. Hence it's safe to
         * clear the TCE entries if firmware assisted dump is active.
         */
        if (!is_kdump_kernel() || is_fadump_active()) {
                /* Clear the table in case firmware left allocations in it */
                ppc_md.tce_free(tbl, tbl->it_offset, tbl->it_size);
                return;
        }

#ifdef CONFIG_CRASH_DUMP
        if (ppc_md.tce_get) {
                unsigned long index, tceval, tcecount = 0;

                /* Reserve the existing mappings left by the first kernel. */
                for (index = 0; index < tbl->it_size; index++) {
                        tceval = ppc_md.tce_get(tbl, index + tbl->it_offset);
                        /*
                         * Freed TCE entry contains 0x7fffffffffffffff on JS20
                         */
                        if (tceval && (tceval != 0x7fffffffffffffffUL)) {
                                __set_bit(index, tbl->it_map);
                                tcecount++;
                        }
                }

                if ((tbl->it_size - tcecount) < KDUMP_MIN_TCE_ENTRIES) {
                        printk(KERN_WARNING "TCE table is full; freeing ");
                        printk(KERN_WARNING "%d entries for the kdump boot\n",
                                KDUMP_MIN_TCE_ENTRIES);
                        for (index = tbl->it_size - KDUMP_MIN_TCE_ENTRIES;
                                index < tbl->it_size; index++)
                                __clear_bit(index, tbl->it_map);
                }
        }
#endif
}

/*
 * Build a iommu_table structure.  This contains a bit map which
 * is used to manage allocation of the tce space.
 */
struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
{
        unsigned long sz;
        static int welcomed = 0;
        struct page *page;
        unsigned int i;
        struct iommu_pool *p;

        /* number of bytes needed for the bitmap */
        sz = (tbl->it_size + 7) >> 3;

        page = alloc_pages_node(nid, GFP_ATOMIC, get_order(sz));
        if (!page)
                panic("iommu_init_table: Can't allocate %ld bytes\n", sz);
        tbl->it_map = page_address(page);
        memset(tbl->it_map, 0, sz);

        /*
         * Reserve page 0 so it will not be used for any mappings.
         * This avoids buggy drivers that consider page 0 to be invalid
         * to crash the machine or even lose data.
         */
        if (tbl->it_offset == 0)
                set_bit(0, tbl->it_map);

        /* We only split the IOMMU table if we have 1GB or more of space */
        if ((tbl->it_size << IOMMU_PAGE_SHIFT) >= (1UL * 1024 * 1024 * 1024))
                tbl->nr_pools = IOMMU_NR_POOLS;
        else
                tbl->nr_pools = 1;

        /* We reserve the top 1/4 of the table for large allocations */
        tbl->poolsize = (tbl->it_size * 3 / 4) / tbl->nr_pools;

        for (i = 0; i < tbl->nr_pools; i++) {
                p = &tbl->pools[i];
                spin_lock_init(&(p->lock));
                p->start = tbl->poolsize * i;
                p->hint = p->start;
                p->end = p->start + tbl->poolsize;
        }

        p = &tbl->large_pool;
        spin_lock_init(&(p->lock));
        p->start = tbl->poolsize * i;
        p->hint = p->start;
        p->end = tbl->it_size;

        iommu_table_clear(tbl);

        if (!welcomed) {
                printk(KERN_INFO "IOMMU table initialized, virtual merging %s\n",
                       novmerge ? "disabled" : "enabled");
                welcomed = 1;
        }

        return tbl;
}

void iommu_free_table(struct iommu_table *tbl, const char *node_name)
{
        unsigned long bitmap_sz, i;
        unsigned int order;

        if (!tbl || !tbl->it_map) {
                printk(KERN_ERR "%s: expected TCE map for %s\n", __func__,
                                node_name);
                return;
        }

        /* verify that table contains no entries */
        /* it_size is in entries, and we're examining 64 at a time */
        for (i = 0; i < (tbl->it_size/64); i++) {
                if (tbl->it_map[i] != 0) {
                        printk(KERN_WARNING "%s: Unexpected TCEs for %s\n",
                                __func__, node_name);
                        break;
                }
        }

        /* calculate bitmap size in bytes */
        bitmap_sz = (tbl->it_size + 7) / 8;

        /* free bitmap */
        order = get_order(bitmap_sz);
        free_pages((unsigned long) tbl->it_map, order);

        /* free table */
        kfree(tbl);
}

/* Creates TCEs for a user provided buffer.  The user buffer must be
 * contiguous real kernel storage (not vmalloc).  The address passed here
 * comprises a page address and offset into that page. The dma_addr_t
 * returned will point to the same byte within the page as was passed in.
 */
dma_addr_t iommu_map_page(struct device *dev, struct iommu_table *tbl,
                          struct page *page, unsigned long offset, size_t size,
                          unsigned long mask, enum dma_data_direction direction,
                          struct dma_attrs *attrs)
{
        dma_addr_t dma_handle = DMA_ERROR_CODE;
        void *vaddr;
        unsigned long uaddr;
        unsigned int npages, align;

        BUG_ON(direction == DMA_NONE);

        vaddr = page_address(page) + offset;
        uaddr = (unsigned long)vaddr;
        npages = iommu_num_pages(uaddr, size, IOMMU_PAGE_SIZE);

        if (tbl) {
                align = 0;
                if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && size >= PAGE_SIZE &&
                    ((unsigned long)vaddr & ~PAGE_MASK) == 0)
                        align = PAGE_SHIFT - IOMMU_PAGE_SHIFT;

                dma_handle = iommu_alloc(dev, tbl, vaddr, npages, direction,
                                         mask >> IOMMU_PAGE_SHIFT, align,
                                         attrs);
                if (dma_handle == DMA_ERROR_CODE) {
                        if (printk_ratelimit())  {
                                dev_info(dev, "iommu_alloc failed, tbl %p "
                                         "vaddr %p npages %d\n", tbl, vaddr,
                                         npages);
                        }
                } else
                        dma_handle |= (uaddr & ~IOMMU_PAGE_MASK);
        }

        return dma_handle;
}

void iommu_unmap_page(struct iommu_table *tbl, dma_addr_t dma_handle,
                      size_t size, enum dma_data_direction direction,
                      struct dma_attrs *attrs)
{
        unsigned int npages;

        BUG_ON(direction == DMA_NONE);

        if (tbl) {
                npages = iommu_num_pages(dma_handle, size, IOMMU_PAGE_SIZE);
                iommu_free(tbl, dma_handle, npages);
        }
}

/* Allocates a contiguous real buffer and creates mappings over it.
 * Returns the virtual address of the buffer and sets dma_handle
 * to the dma address (mapping) of the first page.
 */
void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
                           size_t size, dma_addr_t *dma_handle,
                           unsigned long mask, gfp_t flag, int node)
{
        void *ret = NULL;
        dma_addr_t mapping;
        unsigned int order;
        unsigned int nio_pages, io_order;
        struct page *page;

        size = PAGE_ALIGN(size);
        order = get_order(size);

        /*
         * Client asked for way too much space.  This is checked later
         * anyway.  It is easier to debug here for the drivers than in
         * the tce tables.
         */
        if (order >= IOMAP_MAX_ORDER) {
                dev_info(dev, "iommu_alloc_consistent size too large: 0x%lx\n",
                         size);
                return NULL;
        }

        if (!tbl)
                return NULL;

        /* Alloc enough pages (and possibly more) */
        page = alloc_pages_node(node, flag, order);
        if (!page)
                return NULL;
        ret = page_address(page);
        memset(ret, 0, size);

        /* Set up tces to cover the allocated range */
        nio_pages = size >> IOMMU_PAGE_SHIFT;
        io_order = get_iommu_order(size);
        mapping = iommu_alloc(dev, tbl, ret, nio_pages, DMA_BIDIRECTIONAL,
                              mask >> IOMMU_PAGE_SHIFT, io_order, NULL);
        if (mapping == DMA_ERROR_CODE) {
                free_pages((unsigned long)ret, order);
                return NULL;
        }
        *dma_handle = mapping;
        return ret;
}

void iommu_free_coherent(struct iommu_table *tbl, size_t size,
                         void *vaddr, dma_addr_t dma_handle)
{
        if (tbl) {
                unsigned int nio_pages;

                size = PAGE_ALIGN(size);
                nio_pages = size >> IOMMU_PAGE_SHIFT;
                iommu_free(tbl, dma_handle, nio_pages);
                size = PAGE_ALIGN(size);
                free_pages((unsigned long)vaddr, get_order(size));
        }
}