// SPDX-License-Identifier: GPL-2.0-only
/*
 * Dynamic DMA mapping support.
 *
 * This implementation is a fallback for 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.
 * 05/09/10 linville    Add support for syncing ranges, support syncing for
 *                      DMA_BIDIRECTIONAL mappings, miscellaneous cleanup.
 * 08/12/11 beckyb      Add highmem support
 */

#define pr_fmt(fmt) "software IO TLB: " fmt

#include <linux/cache.h>
#include <linux/dma-direct.h>
#include <linux/dma-map-ops.h>
#include <linux/mm.h>
#include <linux/export.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/swiotlb.h>
#include <linux/pfn.h>
#include <linux/types.h>
#include <linux/ctype.h>
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/scatterlist.h>
#include <linux/cc_platform.h>
#include <linux/set_memory.h>
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#endif
#ifdef CONFIG_DMA_RESTRICTED_POOL
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_fdt.h>
#include <linux/of_reserved_mem.h>
#include <linux/slab.h>
#endif

#include <asm/io.h>
#include <asm/dma.h>

#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/iommu-helper.h>

#define CREATE_TRACE_POINTS
#include <trace/events/swiotlb.h>

#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)

#define INVALID_PHYS_ADDR (~(phys_addr_t)0)

enum swiotlb_force swiotlb_force;

struct io_tlb_mem io_tlb_default_mem;

/*
 * Max segment that we can provide which (if pages are contingous) will
 * not be bounced (unless SWIOTLB_FORCE is set).
 */
static unsigned int max_segment;

static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;

static int __init
setup_io_tlb_npages(char *str)
{
        if (isdigit(*str)) {
                /* avoid tail segment of size < IO_TLB_SEGSIZE */
                default_nslabs =
                        ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
        }
        if (*str == ',')
                ++str;
        if (!strcmp(str, "force"))
                swiotlb_force = SWIOTLB_FORCE;
        else if (!strcmp(str, "noforce"))
                swiotlb_force = SWIOTLB_NO_FORCE;

        return 0;
}
early_param("swiotlb", setup_io_tlb_npages);

unsigned int swiotlb_max_segment(void)
{
        return io_tlb_default_mem.nslabs ? max_segment : 0;
}
EXPORT_SYMBOL_GPL(swiotlb_max_segment);

void swiotlb_set_max_segment(unsigned int val)
{
        if (swiotlb_force == SWIOTLB_FORCE)
                max_segment = 1;
        else
                max_segment = rounddown(val, PAGE_SIZE);
}

unsigned long swiotlb_size_or_default(void)
{
        return default_nslabs << IO_TLB_SHIFT;
}

void __init swiotlb_adjust_size(unsigned long size)
{
        /*
         * If swiotlb parameter has not been specified, give a chance to
         * architectures such as those supporting memory encryption to
         * adjust/expand SWIOTLB size for their use.
         */
        if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
                return;
        size = ALIGN(size, IO_TLB_SIZE);
        default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
        pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
}

void swiotlb_print_info(void)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;

        if (!mem->nslabs) {
                pr_warn("No low mem\n");
                return;
        }

        pr_info("mapped [mem %pa-%pa] (%luMB)\n", &mem->start, &mem->end,
               (mem->nslabs << IO_TLB_SHIFT) >> 20);
}

static inline unsigned long io_tlb_offset(unsigned long val)
{
        return val & (IO_TLB_SEGSIZE - 1);
}

static inline unsigned long nr_slots(u64 val)
{
        return DIV_ROUND_UP(val, IO_TLB_SIZE);
}

/*
 * Early SWIOTLB allocation may be too early to allow an architecture to
 * perform the desired operations.  This function allows the architecture to
 * call SWIOTLB when the operations are possible.  It needs to be called
 * before the SWIOTLB memory is used.
 */
void __init swiotlb_update_mem_attributes(void)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;
        void *vaddr;
        unsigned long bytes;

        if (!mem->nslabs || mem->late_alloc)
                return;
        vaddr = phys_to_virt(mem->start);
        bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
        set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
        memset(vaddr, 0, bytes);
}

static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
                                    unsigned long nslabs, bool late_alloc)
{
        void *vaddr = phys_to_virt(start);
        unsigned long bytes = nslabs << IO_TLB_SHIFT, i;

        mem->nslabs = nslabs;
        mem->start = start;
        mem->end = mem->start + bytes;
        mem->index = 0;
        mem->late_alloc = late_alloc;

        if (swiotlb_force == SWIOTLB_FORCE)
                mem->force_bounce = true;

        spin_lock_init(&mem->lock);
        for (i = 0; i < mem->nslabs; i++) {
                mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
                mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
                mem->slots[i].alloc_size = 0;
        }
        memset(vaddr, 0, bytes);
}

int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;
        size_t alloc_size;

        if (swiotlb_force == SWIOTLB_NO_FORCE)
                return 0;

        /* protect against double initialization */
        if (WARN_ON_ONCE(mem->nslabs))
                return -ENOMEM;

        alloc_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), nslabs));
        mem->slots = memblock_alloc(alloc_size, PAGE_SIZE);
        if (!mem->slots)
                panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
                      __func__, alloc_size, PAGE_SIZE);

        swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);

        if (verbose)
                swiotlb_print_info();
        swiotlb_set_max_segment(mem->nslabs << IO_TLB_SHIFT);
        return 0;
}

/*
 * Statically reserve bounce buffer space and initialize bounce buffer data
 * structures for the software IO TLB used to implement the DMA API.
 */
void  __init
swiotlb_init(int verbose)
{
        size_t bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
        void *tlb;

        if (swiotlb_force == SWIOTLB_NO_FORCE)
                return;

        /* Get IO TLB memory from the low pages */
        tlb = memblock_alloc_low(bytes, PAGE_SIZE);
        if (!tlb)
                goto fail;
        if (swiotlb_init_with_tbl(tlb, default_nslabs, verbose))
                goto fail_free_mem;
        return;

fail_free_mem:
        memblock_free(tlb, bytes);
fail:
        pr_warn("Cannot allocate buffer");
}

/*
 * 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 nslabs =
                ALIGN(default_size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
        unsigned long bytes;
        unsigned char *vstart = NULL;
        unsigned int order;
        int rc = 0;

        if (swiotlb_force == SWIOTLB_NO_FORCE)
                return 0;

        /*
         * Get IO TLB memory from the low pages
         */
        order = get_order(nslabs << IO_TLB_SHIFT);
        nslabs = SLABS_PER_PAGE << order;
        bytes = nslabs << IO_TLB_SHIFT;

        while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
                vstart = (void *)__get_free_pages(GFP_DMA | __GFP_NOWARN,
                                                  order);
                if (vstart)
                        break;
                order--;
        }

        if (!vstart)
                return -ENOMEM;

        if (order != get_order(bytes)) {
                pr_warn("only able to allocate %ld MB\n",
                        (PAGE_SIZE << order) >> 20);
                nslabs = SLABS_PER_PAGE << order;
        }
        rc = swiotlb_late_init_with_tbl(vstart, nslabs);
        if (rc)
                free_pages((unsigned long)vstart, order);

        return rc;
}

int
swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;
        unsigned long bytes = nslabs << IO_TLB_SHIFT;

        if (swiotlb_force == SWIOTLB_NO_FORCE)
                return 0;

        /* protect against double initialization */
        if (WARN_ON_ONCE(mem->nslabs))
                return -ENOMEM;

        mem->slots = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
                get_order(array_size(sizeof(*mem->slots), nslabs)));
        if (!mem->slots)
                return -ENOMEM;

        set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT);
        swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);

        swiotlb_print_info();
        swiotlb_set_max_segment(mem->nslabs << IO_TLB_SHIFT);
        return 0;
}

void __init swiotlb_exit(void)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;
        unsigned long tbl_vaddr;
        size_t tbl_size, slots_size;

        if (!mem->nslabs)
                return;

        pr_info("tearing down default memory pool\n");
        tbl_vaddr = (unsigned long)phys_to_virt(mem->start);
        tbl_size = PAGE_ALIGN(mem->end - mem->start);
        slots_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), mem->nslabs));

        set_memory_encrypted(tbl_vaddr, tbl_size >> PAGE_SHIFT);
        if (mem->late_alloc) {
                free_pages(tbl_vaddr, get_order(tbl_size));
                free_pages((unsigned long)mem->slots, get_order(slots_size));
        } else {
                memblock_free_late(mem->start, tbl_size);
                memblock_free_late(__pa(mem->slots), slots_size);
        }

        memset(mem, 0, sizeof(*mem));
}

/*
 * Return the offset into a iotlb slot required to keep the device happy.
 */
static unsigned int swiotlb_align_offset(struct device *dev, u64 addr)
{
        return addr & dma_get_min_align_mask(dev) & (IO_TLB_SIZE - 1);
}

/*
 * Bounce: copy the swiotlb buffer from or back to the original dma location
 */
static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size,
                           enum dma_data_direction dir)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
        int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
        phys_addr_t orig_addr = mem->slots[index].orig_addr;
        size_t alloc_size = mem->slots[index].alloc_size;
        unsigned long pfn = PFN_DOWN(orig_addr);
        unsigned char *vaddr = phys_to_virt(tlb_addr);
        unsigned int tlb_offset, orig_addr_offset;

        if (orig_addr == INVALID_PHYS_ADDR)
                return;

        tlb_offset = tlb_addr & (IO_TLB_SIZE - 1);
        orig_addr_offset = swiotlb_align_offset(dev, orig_addr);
        if (tlb_offset < orig_addr_offset) {
                dev_WARN_ONCE(dev, 1,
                        "Access before mapping start detected. orig offset %u, requested offset %u.\n",
                        orig_addr_offset, tlb_offset);
                return;
        }

        tlb_offset -= orig_addr_offset;
        if (tlb_offset > alloc_size) {
                dev_WARN_ONCE(dev, 1,
                        "Buffer overflow detected. Allocation size: %zu. Mapping size: %zu+%u.\n",
                        alloc_size, size, tlb_offset);
                return;
        }

        orig_addr += tlb_offset;
        alloc_size -= tlb_offset;

        if (size > alloc_size) {
                dev_WARN_ONCE(dev, 1,
                        "Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
                        alloc_size, size);
                size = alloc_size;
        }

        if (PageHighMem(pfn_to_page(pfn))) {
                /* The buffer does not have a mapping.  Map it in and copy */
                unsigned int offset = orig_addr & ~PAGE_MASK;
                char *buffer;
                unsigned int sz = 0;
                unsigned long flags;

                while (size) {
                        sz = min_t(size_t, PAGE_SIZE - offset, size);

                        local_irq_save(flags);
                        buffer = kmap_atomic(pfn_to_page(pfn));
                        if (dir == DMA_TO_DEVICE)
                                memcpy(vaddr, buffer + offset, sz);
                        else
                                memcpy(buffer + offset, vaddr, sz);
                        kunmap_atomic(buffer);
                        local_irq_restore(flags);

                        size -= sz;
                        pfn++;
                        vaddr += sz;
                        offset = 0;
                }
        } else if (dir == DMA_TO_DEVICE) {
                memcpy(vaddr, phys_to_virt(orig_addr), size);
        } else {
                memcpy(phys_to_virt(orig_addr), vaddr, size);
        }
}

#define slot_addr(start, idx)   ((start) + ((idx) << IO_TLB_SHIFT))

/*
 * Carefully handle integer overflow which can occur when boundary_mask == ~0UL.
 */
static inline unsigned long get_max_slots(unsigned long boundary_mask)
{
        if (boundary_mask == ~0UL)
                return 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
        return nr_slots(boundary_mask + 1);
}

static unsigned int wrap_index(struct io_tlb_mem *mem, unsigned int index)
{
        if (index >= mem->nslabs)
                return 0;
        return index;
}

/*
 * Find a suitable number of IO TLB entries size that will fit this request and
 * allocate a buffer from that IO TLB pool.
 */
static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
                              size_t alloc_size, unsigned int alloc_align_mask)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
        unsigned long boundary_mask = dma_get_seg_boundary(dev);
        dma_addr_t tbl_dma_addr =
                phys_to_dma_unencrypted(dev, mem->start) & boundary_mask;
        unsigned long max_slots = get_max_slots(boundary_mask);
        unsigned int iotlb_align_mask =
                dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1);
        unsigned int nslots = nr_slots(alloc_size), stride;
        unsigned int index, wrap, count = 0, i;
        unsigned int offset = swiotlb_align_offset(dev, orig_addr);
        unsigned long flags;

        BUG_ON(!nslots);

        /*
         * For mappings with an alignment requirement don't bother looping to
         * unaligned slots once we found an aligned one.  For allocations of
         * PAGE_SIZE or larger only look for page aligned allocations.
         */
        stride = (iotlb_align_mask >> IO_TLB_SHIFT) + 1;
        if (alloc_size >= PAGE_SIZE)
                stride = max(stride, stride << (PAGE_SHIFT - IO_TLB_SHIFT));
        stride = max(stride, (alloc_align_mask >> IO_TLB_SHIFT) + 1);

        spin_lock_irqsave(&mem->lock, flags);
        if (unlikely(nslots > mem->nslabs - mem->used))
                goto not_found;

        index = wrap = wrap_index(mem, ALIGN(mem->index, stride));
        do {
                if (orig_addr &&
                    (slot_addr(tbl_dma_addr, index) & iotlb_align_mask) !=
                            (orig_addr & iotlb_align_mask)) {
                        index = wrap_index(mem, index + 1);
                        continue;
                }

                /*
                 * 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 (!iommu_is_span_boundary(index, nslots,
                                            nr_slots(tbl_dma_addr),
                                            max_slots)) {
                        if (mem->slots[index].list >= nslots)
                                goto found;
                }
                index = wrap_index(mem, index + stride);
        } while (index != wrap);

not_found:
        spin_unlock_irqrestore(&mem->lock, flags);
        return -1;

found:
        for (i = index; i < index + nslots; i++) {
                mem->slots[i].list = 0;
                mem->slots[i].alloc_size =
                        alloc_size - (offset + ((i - index) << IO_TLB_SHIFT));
        }
        for (i = index - 1;
             io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 &&
             mem->slots[i].list; i--)
                mem->slots[i].list = ++count;

        /*
         * Update the indices to avoid searching in the next round.
         */
        if (index + nslots < mem->nslabs)
                mem->index = index + nslots;
        else
                mem->index = 0;
        mem->used += nslots;

        spin_unlock_irqrestore(&mem->lock, flags);
        return index;
}

phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
                size_t mapping_size, size_t alloc_size,
                unsigned int alloc_align_mask, enum dma_data_direction dir,
                unsigned long attrs)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
        unsigned int offset = swiotlb_align_offset(dev, orig_addr);
        unsigned int i;
        int index;
        phys_addr_t tlb_addr;

        if (!mem)
                panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");

        if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
                pr_warn_once("Memory encryption is active and system is using DMA bounce buffers\n");

        if (mapping_size > alloc_size) {
                dev_warn_once(dev, "Invalid sizes (mapping: %zd bytes, alloc: %zd bytes)",
                              mapping_size, alloc_size);
                return (phys_addr_t)DMA_MAPPING_ERROR;
        }

        index = swiotlb_find_slots(dev, orig_addr,
                                   alloc_size + offset, alloc_align_mask);
        if (index == -1) {
                if (!(attrs & DMA_ATTR_NO_WARN))
                        dev_warn_ratelimited(dev,
        "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",
                                 alloc_size, mem->nslabs, mem->used);
                return (phys_addr_t)DMA_MAPPING_ERROR;
        }

        /*
         * 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.
         */
        for (i = 0; i < nr_slots(alloc_size + offset); i++)
                mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
        tlb_addr = slot_addr(mem->start, index) + offset;
        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
            (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
                swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
        return tlb_addr;
}

static void swiotlb_release_slots(struct device *dev, phys_addr_t tlb_addr)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
        unsigned long flags;
        unsigned int offset = swiotlb_align_offset(dev, tlb_addr);
        int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT;
        int nslots = nr_slots(mem->slots[index].alloc_size + offset);
        int count, i;

        /*
         * Return the buffer to the free list by setting the corresponding
         * entries to indicate the number of contiguous 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(&mem->lock, flags);
        if (index + nslots < ALIGN(index + 1, IO_TLB_SEGSIZE))
                count = mem->slots[index + nslots].list;
        else
                count = 0;

        /*
         * Step 1: return the slots to the free list, merging the slots with
         * superceeding slots
         */
        for (i = index + nslots - 1; i >= index; i--) {
                mem->slots[i].list = ++count;
                mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
                mem->slots[i].alloc_size = 0;
        }

        /*
         * Step 2: merge the returned slots with the preceding slots, if
         * available (non zero)
         */
        for (i = index - 1;
             io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 && mem->slots[i].list;
             i--)
                mem->slots[i].list = ++count;
        mem->used -= nslots;
        spin_unlock_irqrestore(&mem->lock, flags);
}

/*
 * tlb_addr is the physical address of the bounce buffer to unmap.
 */
void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
                              size_t mapping_size, enum dma_data_direction dir,
                              unsigned long attrs)
{
        /*
         * First, sync the memory before unmapping the entry
         */
        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
            (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
                swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_FROM_DEVICE);

        swiotlb_release_slots(dev, tlb_addr);
}

void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
                size_t size, enum dma_data_direction dir)
{
        if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
                swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE);
        else
                BUG_ON(dir != DMA_FROM_DEVICE);
}

void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
                size_t size, enum dma_data_direction dir)
{
        if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
                swiotlb_bounce(dev, tlb_addr, size, DMA_FROM_DEVICE);
        else
                BUG_ON(dir != DMA_TO_DEVICE);
}

/*
 * Create a swiotlb mapping for the buffer at @paddr, and in case of DMAing
 * to the device copy the data into it as well.
 */
dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
                enum dma_data_direction dir, unsigned long attrs)
{
        phys_addr_t swiotlb_addr;
        dma_addr_t dma_addr;

        trace_swiotlb_bounced(dev, phys_to_dma(dev, paddr), size,
                              swiotlb_force);

        swiotlb_addr = swiotlb_tbl_map_single(dev, paddr, size, size, 0, dir,
                        attrs);
        if (swiotlb_addr == (phys_addr_t)DMA_MAPPING_ERROR)
                return DMA_MAPPING_ERROR;

        /* Ensure that the address returned is DMA'ble */
        dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
        if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
                swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir,
                        attrs | DMA_ATTR_SKIP_CPU_SYNC);
                dev_WARN_ONCE(dev, 1,
                        "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
                        &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
                return DMA_MAPPING_ERROR;
        }

        if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
                arch_sync_dma_for_device(swiotlb_addr, size, dir);
        return dma_addr;
}

size_t swiotlb_max_mapping_size(struct device *dev)
{
        return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE;
}

bool is_swiotlb_active(struct device *dev)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;

        return mem && mem->nslabs;
}
EXPORT_SYMBOL_GPL(is_swiotlb_active);

#ifdef CONFIG_DEBUG_FS
static struct dentry *debugfs_dir;

static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem)
{
        debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs);
        debugfs_create_ulong("io_tlb_used", 0400, mem->debugfs, &mem->used);
}

static int __init swiotlb_create_default_debugfs(void)
{
        struct io_tlb_mem *mem = &io_tlb_default_mem;

        debugfs_dir = debugfs_create_dir("swiotlb", NULL);
        if (mem->nslabs) {
                mem->debugfs = debugfs_dir;
                swiotlb_create_debugfs_files(mem);
        }
        return 0;
}

late_initcall(swiotlb_create_default_debugfs);

#endif

#ifdef CONFIG_DMA_RESTRICTED_POOL

#ifdef CONFIG_DEBUG_FS
static void rmem_swiotlb_debugfs_init(struct reserved_mem *rmem)
{
        struct io_tlb_mem *mem = rmem->priv;

        mem->debugfs = debugfs_create_dir(rmem->name, debugfs_dir);
        swiotlb_create_debugfs_files(mem);
}
#else
static void rmem_swiotlb_debugfs_init(struct reserved_mem *rmem)
{
}
#endif

struct page *swiotlb_alloc(struct device *dev, size_t size)
{
        struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
        phys_addr_t tlb_addr;
        int index;

        if (!mem)
                return NULL;

        index = swiotlb_find_slots(dev, 0, size, 0);
        if (index == -1)
                return NULL;

        tlb_addr = slot_addr(mem->start, index);

        return pfn_to_page(PFN_DOWN(tlb_addr));
}

bool swiotlb_free(struct device *dev, struct page *page, size_t size)
{
        phys_addr_t tlb_addr = page_to_phys(page);

        if (!is_swiotlb_buffer(dev, tlb_addr))
                return false;

        swiotlb_release_slots(dev, tlb_addr);

        return true;
}

static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
                                    struct device *dev)
{
        struct io_tlb_mem *mem = rmem->priv;
        unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;

        /*
         * Since multiple devices can share the same pool, the private data,
         * io_tlb_mem struct, will be initialized by the first device attached
         * to it.
         */
        if (!mem) {
                mem = kzalloc(sizeof(*mem), GFP_KERNEL);
                if (!mem)
                        return -ENOMEM;

                mem->slots = kzalloc(array_size(sizeof(*mem->slots), nslabs),
                                     GFP_KERNEL);
                if (!mem->slots) {
                        kfree(mem);
                        return -ENOMEM;
                }

                set_memory_decrypted((unsigned long)phys_to_virt(rmem->base),
                                     rmem->size >> PAGE_SHIFT);
                swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false);
                mem->force_bounce = true;
                mem->for_alloc = true;

                rmem->priv = mem;

                rmem_swiotlb_debugfs_init(rmem);
        }

        dev->dma_io_tlb_mem = mem;

        return 0;
}

static void rmem_swiotlb_device_release(struct reserved_mem *rmem,
                                        struct device *dev)
{
        dev->dma_io_tlb_mem = &io_tlb_default_mem;
}

static const struct reserved_mem_ops rmem_swiotlb_ops = {
        .device_init = rmem_swiotlb_device_init,
        .device_release = rmem_swiotlb_device_release,
};

static int __init rmem_swiotlb_setup(struct reserved_mem *rmem)
{
        unsigned long node = rmem->fdt_node;

        if (of_get_flat_dt_prop(node, "reusable", NULL) ||
            of_get_flat_dt_prop(node, "linux,cma-default", NULL) ||
            of_get_flat_dt_prop(node, "linux,dma-default", NULL) ||
            of_get_flat_dt_prop(node, "no-map", NULL))
                return -EINVAL;

        if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
                pr_err("Restricted DMA pool must be accessible within the linear mapping.");
                return -EINVAL;
        }

        rmem->ops = &rmem_swiotlb_ops;
        pr_info("Reserved memory: created restricted DMA pool at %pa, size %ld MiB\n",
                &rmem->base, (unsigned long)rmem->size / SZ_1M);
        return 0;
}

RESERVEDMEM_OF_DECLARE(dma, "restricted-dma-pool", rmem_swiotlb_setup);
#endif /* CONFIG_DMA_RESTRICTED_POOL */