Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1063 insertions, 0 deletions

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
new file mode 100644
index 000000000..8b1360772
--- /dev/null
+++ b/kernel/dma/swiotlb.c
@@ -0,0 +1,1063 @@
+/*
+ * 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/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/mem_encrypt.h>
+#include <linux/set_memory.h>
+
+#include <asm/io.h>
+#include <asm/dma.h>
+
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/iommu-helper.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/swiotlb.h>
+
+#define OFFSET(val,align) ((unsigned long)	\
+	                   ( (val) & ( (align) - 1)))
+
+#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)
+
+enum swiotlb_force swiotlb_force;
+
+/*
+ * Used to do a quick range check in swiotlb_tbl_unmap_single and
+ * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
+ * API.
+ */
+static phys_addr_t io_tlb_start, io_tlb_end;
+
+/*
+ * The number of IO TLB blocks (in groups of 64) between 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;
+
+static phys_addr_t 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;
+
+/*
+ * Max segment that we can provide which (if pages are contingous) will
+ * not be bounced (unless SWIOTLB_FORCE is set).
+ */
+unsigned int max_segment;
+
+/*
+ * We need to save away the original address corresponding to a mapped entry
+ * for the sync operations.
+ */
+#define INVALID_PHYS_ADDR (~(phys_addr_t)0)
+static phys_addr_t *io_tlb_orig_addr;
+
+/*
+ * Protect the above data structures in the map and unmap calls
+ */
+static DEFINE_SPINLOCK(io_tlb_lock);
+
+static int late_alloc;
+
+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 = SWIOTLB_FORCE;
+	} else if (!strcmp(str, "noforce")) {
+		swiotlb_force = SWIOTLB_NO_FORCE;
+		io_tlb_nslabs = 1;
+	}
+
+	return 0;
+}
+early_param("swiotlb", setup_io_tlb_npages);
+/* make io_tlb_overflow tunable too? */
+
+unsigned long swiotlb_nr_tbl(void)
+{
+	return io_tlb_nslabs;
+}
+EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
+
+unsigned int swiotlb_max_segment(void)
+{
+	return max_segment;
+}
+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);
+}
+
+/* default to 64MB */
+#define IO_TLB_DEFAULT_SIZE (64UL<<20)
+unsigned long swiotlb_size_or_default(void)
+{
+	unsigned long size;
+
+	size = io_tlb_nslabs << IO_TLB_SHIFT;
+
+	return size ? size : (IO_TLB_DEFAULT_SIZE);
+}
+
+static bool no_iotlb_memory;
+
+void swiotlb_print_info(void)
+{
+	unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;
+
+	if (no_iotlb_memory) {
+		pr_warn("No low mem\n");
+		return;
+	}
+
+	pr_info("mapped [mem %#010llx-%#010llx] (%luMB)\n",
+	       (unsigned long long)io_tlb_start,
+	       (unsigned long long)io_tlb_end,
+	       bytes >> 20);
+}
+
+/*
+ * 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)
+{
+	void *vaddr;
+	unsigned long bytes;
+
+	if (no_iotlb_memory || late_alloc)
+		return;
+
+	vaddr = phys_to_virt(io_tlb_start);
+	bytes = PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT);
+	set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
+	memset(vaddr, 0, bytes);
+
+	vaddr = phys_to_virt(io_tlb_overflow_buffer);
+	bytes = PAGE_ALIGN(io_tlb_overflow);
+	set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
+	memset(vaddr, 0, bytes);
+}
+
+int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
+{
+	void *v_overflow_buffer;
+	unsigned long i, bytes;
+
+	bytes = nslabs << IO_TLB_SHIFT;
+
+	io_tlb_nslabs = nslabs;
+	io_tlb_start = __pa(tlb);
+	io_tlb_end = io_tlb_start + bytes;
+
+	/*
+	 * Get the overflow emergency buffer
+	 */
+	v_overflow_buffer = memblock_virt_alloc_low_nopanic(
+						PAGE_ALIGN(io_tlb_overflow),
+						PAGE_SIZE);
+	if (!v_overflow_buffer)
+		return -ENOMEM;
+
+	io_tlb_overflow_buffer = __pa(v_overflow_buffer);
+
+	/*
+	 * 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 = memblock_virt_alloc(
+				PAGE_ALIGN(io_tlb_nslabs * sizeof(int)),
+				PAGE_SIZE);
+	io_tlb_orig_addr = memblock_virt_alloc(
+				PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)),
+				PAGE_SIZE);
+	for (i = 0; i < io_tlb_nslabs; i++) {
+		io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+		io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+	}
+	io_tlb_index = 0;
+	no_iotlb_memory = false;
+
+	if (verbose)
+		swiotlb_print_info();
+
+	swiotlb_set_max_segment(io_tlb_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 default_size = IO_TLB_DEFAULT_SIZE;
+	unsigned char *vstart;
+	unsigned long bytes;
+
+	if (!io_tlb_nslabs) {
+		io_tlb_nslabs = (default_size >> IO_TLB_SHIFT);
+		io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+	}
+
+	bytes = io_tlb_nslabs << IO_TLB_SHIFT;
+
+	/* Get IO TLB memory from the low pages */
+	vstart = memblock_virt_alloc_low_nopanic(PAGE_ALIGN(bytes), PAGE_SIZE);
+	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose))
+		return;
+
+	if (io_tlb_start) {
+		memblock_free_early(io_tlb_start,
+				    PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
+		io_tlb_start = 0;
+	}
+	pr_warn("Cannot allocate buffer");
+	no_iotlb_memory = true;
+}
+
+/*
+ * 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 bytes, req_nslabs = io_tlb_nslabs;
+	unsigned char *vstart = NULL;
+	unsigned int order;
+	int rc = 0;
+
+	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 << IO_TLB_SHIFT);
+	io_tlb_nslabs = SLABS_PER_PAGE << order;
+	bytes = io_tlb_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) {
+		io_tlb_nslabs = req_nslabs;
+		return -ENOMEM;
+	}
+	if (order != get_order(bytes)) {
+		pr_warn("only able to allocate %ld MB\n",
+			(PAGE_SIZE << order) >> 20);
+		io_tlb_nslabs = SLABS_PER_PAGE << order;
+	}
+	rc = swiotlb_late_init_with_tbl(vstart, io_tlb_nslabs);
+	if (rc)
+		free_pages((unsigned long)vstart, order);
+
+	return rc;
+}
+
+int
+swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
+{
+	unsigned long i, bytes;
+	unsigned char *v_overflow_buffer;
+
+	bytes = nslabs << IO_TLB_SHIFT;
+
+	io_tlb_nslabs = nslabs;
+	io_tlb_start = virt_to_phys(tlb);
+	io_tlb_end = io_tlb_start + bytes;
+
+	set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT);
+	memset(tlb, 0, bytes);
+
+	/*
+	 * Get the overflow emergency buffer
+	 */
+	v_overflow_buffer = (void *)__get_free_pages(GFP_DMA,
+						     get_order(io_tlb_overflow));
+	if (!v_overflow_buffer)
+		goto cleanup2;
+
+	set_memory_decrypted((unsigned long)v_overflow_buffer,
+			io_tlb_overflow >> PAGE_SHIFT);
+	memset(v_overflow_buffer, 0, io_tlb_overflow);
+	io_tlb_overflow_buffer = virt_to_phys(v_overflow_buffer);
+
+	/*
+	 * 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 cleanup3;
+
+	io_tlb_orig_addr = (phys_addr_t *)
+		__get_free_pages(GFP_KERNEL,
+				 get_order(io_tlb_nslabs *
+					   sizeof(phys_addr_t)));
+	if (!io_tlb_orig_addr)
+		goto cleanup4;
+
+	for (i = 0; i < io_tlb_nslabs; i++) {
+		io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+		io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+	}
+	io_tlb_index = 0;
+	no_iotlb_memory = false;
+
+	swiotlb_print_info();
+
+	late_alloc = 1;
+
+	swiotlb_set_max_segment(io_tlb_nslabs << IO_TLB_SHIFT);
+
+	return 0;
+
+cleanup4:
+	free_pages((unsigned long)io_tlb_list, get_order(io_tlb_nslabs *
+	                                                 sizeof(int)));
+	io_tlb_list = NULL;
+cleanup3:
+	free_pages((unsigned long)v_overflow_buffer,
+		   get_order(io_tlb_overflow));
+	io_tlb_overflow_buffer = 0;
+cleanup2:
+	io_tlb_end = 0;
+	io_tlb_start = 0;
+	io_tlb_nslabs = 0;
+	max_segment = 0;
+	return -ENOMEM;
+}
+
+void __init swiotlb_exit(void)
+{
+	if (!io_tlb_orig_addr)
+		return;
+
+	if (late_alloc) {
+		free_pages((unsigned long)phys_to_virt(io_tlb_overflow_buffer),
+			   get_order(io_tlb_overflow));
+		free_pages((unsigned long)io_tlb_orig_addr,
+			   get_order(io_tlb_nslabs * sizeof(phys_addr_t)));
+		free_pages((unsigned long)io_tlb_list, get_order(io_tlb_nslabs *
+								 sizeof(int)));
+		free_pages((unsigned long)phys_to_virt(io_tlb_start),
+			   get_order(io_tlb_nslabs << IO_TLB_SHIFT));
+	} else {
+		memblock_free_late(io_tlb_overflow_buffer,
+				   PAGE_ALIGN(io_tlb_overflow));
+		memblock_free_late(__pa(io_tlb_orig_addr),
+				   PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)));
+		memblock_free_late(__pa(io_tlb_list),
+				   PAGE_ALIGN(io_tlb_nslabs * sizeof(int)));
+		memblock_free_late(io_tlb_start,
+				   PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
+	}
+	io_tlb_nslabs = 0;
+	max_segment = 0;
+}
+
+int is_swiotlb_buffer(phys_addr_t paddr)
+{
+	return paddr >= io_tlb_start && paddr < io_tlb_end;
+}
+
+/*
+ * Bounce: copy the swiotlb buffer back to the original dma location
+ */
+static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
+			   size_t size, enum dma_data_direction dir)
+{
+	unsigned long pfn = PFN_DOWN(orig_addr);
+	unsigned char *vaddr = phys_to_virt(tlb_addr);
+
+	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);
+	}
+}
+
+phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
+				   dma_addr_t tbl_dma_addr,
+				   phys_addr_t orig_addr, size_t size,
+				   enum dma_data_direction dir,
+				   unsigned long attrs)
+{
+	unsigned long flags;
+	phys_addr_t tlb_addr;
+	unsigned int nslots, stride, index, wrap;
+	int i;
+	unsigned long mask;
+	unsigned long offset_slots;
+	unsigned long max_slots;
+
+	if (no_iotlb_memory)
+		panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");
+
+	if (mem_encrypt_active())
+		pr_warn_once("%s is active and system is using DMA bounce buffers\n",
+			     sme_active() ? "SME" : "SEV");
+
+	mask = dma_get_seg_boundary(hwdev);
+
+	tbl_dma_addr &= mask;
+
+	offset_slots = ALIGN(tbl_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+
+	/*
+ 	 * Carefully handle integer overflow which can occur when mask == ~0UL.
+ 	 */
+	max_slots = mask + 1
+		    ? ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT
+		    : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
+
+	/*
+	 * For mappings greater than or equal to 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;
+
+	BUG_ON(!nslots);
+
+	/*
+	 * 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);
+	index = ALIGN(io_tlb_index, stride);
+	if (index >= io_tlb_nslabs)
+		index = 0;
+	wrap = index;
+
+	do {
+		while (iommu_is_span_boundary(index, nslots, offset_slots,
+					      max_slots)) {
+			index += stride;
+			if (index >= io_tlb_nslabs)
+				index = 0;
+			if (index == wrap)
+				goto not_found;
+		}
+
+		/*
+		 * 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;
+			tlb_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);
+
+not_found:
+	spin_unlock_irqrestore(&io_tlb_lock, flags);
+	if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit())
+		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
+	return SWIOTLB_MAP_ERROR;
+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.
+	 */
+	for (i = 0; i < nslots; i++)
+		io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
+	/*
+	 * When dir == DMA_FROM_DEVICE we could omit the copy from the orig
+	 * to the tlb buffer, if we knew for sure the device will
+	 * overwirte the entire current content. But we don't. Thus
+	 * unconditional bounce may prevent leaking swiotlb content (i.e.
+	 * kernel memory) to user-space.
+	 */
+	swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE);
+	return tlb_addr;
+}
+
+/*
+ * Allocates bounce buffer and returns its physical address.
+ */
+static phys_addr_t
+map_single(struct device *hwdev, phys_addr_t phys, size_t size,
+	   enum dma_data_direction dir, unsigned long attrs)
+{
+	dma_addr_t start_dma_addr;
+
+	if (swiotlb_force == SWIOTLB_NO_FORCE) {
+		dev_warn_ratelimited(hwdev, "Cannot do DMA to address %pa\n",
+				     &phys);
+		return SWIOTLB_MAP_ERROR;
+	}
+
+	start_dma_addr = __phys_to_dma(hwdev, io_tlb_start);
+	return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size,
+				      dir, attrs);
+}
+
+/*
+ * tlb_addr is the physical address of the bounce buffer to unmap.
+ */
+void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
+			      size_t size, enum dma_data_direction dir,
+			      unsigned long attrs)
+{
+	unsigned long flags;
+	int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+	int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
+	phys_addr_t orig_addr = io_tlb_orig_addr[index];
+
+	/*
+	 * First, sync the memory before unmapping the entry
+	 */
+	if (orig_addr != INVALID_PHYS_ADDR &&
+	    !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+	    ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
+		swiotlb_bounce(orig_addr, tlb_addr, size, DMA_FROM_DEVICE);
+
+	/*
+	 * 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(&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;
+			io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+		}
+		/*
+		 * 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);
+}
+
+void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
+			     size_t size, enum dma_data_direction dir,
+			     enum dma_sync_target target)
+{
+	int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
+	phys_addr_t orig_addr = io_tlb_orig_addr[index];
+
+	if (orig_addr == INVALID_PHYS_ADDR)
+		return;
+	orig_addr += (unsigned long)tlb_addr & ((1 << IO_TLB_SHIFT) - 1);
+
+	switch (target) {
+	case SYNC_FOR_CPU:
+		if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
+			swiotlb_bounce(orig_addr, tlb_addr,
+				       size, DMA_FROM_DEVICE);
+		else
+			BUG_ON(dir != DMA_TO_DEVICE);
+		break;
+	case SYNC_FOR_DEVICE:
+		if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
+			swiotlb_bounce(orig_addr, tlb_addr,
+				       size, DMA_TO_DEVICE);
+		else
+			BUG_ON(dir != DMA_FROM_DEVICE);
+		break;
+	default:
+		BUG();
+	}
+}
+
+static inline bool dma_coherent_ok(struct device *dev, dma_addr_t addr,
+		size_t size)
+{
+	u64 mask = DMA_BIT_MASK(32);
+
+	if (dev && dev->coherent_dma_mask)
+		mask = dev->coherent_dma_mask;
+	return addr + size - 1 <= mask;
+}
+
+static void *
+swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
+		unsigned long attrs)
+{
+	phys_addr_t phys_addr;
+
+	if (swiotlb_force == SWIOTLB_NO_FORCE)
+		goto out_warn;
+
+	phys_addr = swiotlb_tbl_map_single(dev,
+			__phys_to_dma(dev, io_tlb_start),
+			0, size, DMA_FROM_DEVICE, attrs);
+	if (phys_addr == SWIOTLB_MAP_ERROR)
+		goto out_warn;
+
+	*dma_handle = __phys_to_dma(dev, phys_addr);
+	if (!dma_coherent_ok(dev, *dma_handle, size))
+		goto out_unmap;
+
+	memset(phys_to_virt(phys_addr), 0, size);
+	return phys_to_virt(phys_addr);
+
+out_unmap:
+	dev_warn(dev, "hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
+		(unsigned long long)dev->coherent_dma_mask,
+		(unsigned long long)*dma_handle);
+
+	/*
+	 * DMA_TO_DEVICE to avoid memcpy in unmap_single.
+	 * DMA_ATTR_SKIP_CPU_SYNC is optional.
+	 */
+	swiotlb_tbl_unmap_single(dev, phys_addr, size, DMA_TO_DEVICE,
+			DMA_ATTR_SKIP_CPU_SYNC);
+out_warn:
+	if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit()) {
+		dev_warn(dev,
+			"swiotlb: coherent allocation failed, size=%zu\n",
+			size);
+		dump_stack();
+	}
+	return NULL;
+}
+
+static bool swiotlb_free_buffer(struct device *dev, size_t size,
+		dma_addr_t dma_addr)
+{
+	phys_addr_t phys_addr = dma_to_phys(dev, dma_addr);
+
+	WARN_ON_ONCE(irqs_disabled());
+
+	if (!is_swiotlb_buffer(phys_addr))
+		return false;
+
+	/*
+	 * DMA_TO_DEVICE to avoid memcpy in swiotlb_tbl_unmap_single.
+	 * DMA_ATTR_SKIP_CPU_SYNC is optional.
+	 */
+	swiotlb_tbl_unmap_single(dev, phys_addr, size, DMA_TO_DEVICE,
+				 DMA_ATTR_SKIP_CPU_SYNC);
+	return true;
+}
+
+/*
+ * Map a single buffer of the indicated size for DMA in streaming mode.  The
+ * physical address to use is returned.
+ *
+ * Once the device is given the dma address, the device owns this memory until
+ * either swiotlb_unmap_page or swiotlb_dma_sync_single is performed.
+ */
+dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
+			    unsigned long offset, size_t size,
+			    enum dma_data_direction dir,
+			    unsigned long attrs)
+{
+	phys_addr_t map, phys = page_to_phys(page) + offset;
+	dma_addr_t dev_addr = phys_to_dma(dev, phys);
+
+	BUG_ON(dir == DMA_NONE);
+	/*
+	 * If the address happens to be in the device's DMA window,
+	 * we can safely return the device addr and not worry about bounce
+	 * buffering it.
+	 */
+	if (dma_capable(dev, dev_addr, size) && swiotlb_force != SWIOTLB_FORCE)
+		return dev_addr;
+
+	trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);
+
+	/* Oh well, have to allocate and map a bounce buffer. */
+	map = map_single(dev, phys, size, dir, attrs);
+	if (map == SWIOTLB_MAP_ERROR)
+		return __phys_to_dma(dev, io_tlb_overflow_buffer);
+
+	dev_addr = __phys_to_dma(dev, map);
+
+	/* Ensure that the address returned is DMA'ble */
+	if (dma_capable(dev, dev_addr, size))
+		return dev_addr;
+
+	attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+	swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
+
+	return __phys_to_dma(dev, io_tlb_overflow_buffer);
+}
+
+/*
+ * Unmap a single streaming mode DMA translation.  The dma_addr and size must
+ * match what was provided for in a previous swiotlb_map_page 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.
+ */
+static void unmap_single(struct device *hwdev, dma_addr_t dev_addr,
+			 size_t size, enum dma_data_direction dir,
+			 unsigned long attrs)
+{
+	phys_addr_t paddr = dma_to_phys(hwdev, dev_addr);
+
+	BUG_ON(dir == DMA_NONE);
+
+	if (is_swiotlb_buffer(paddr)) {
+		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
+		return;
+	}
+
+	if (dir != DMA_FROM_DEVICE)
+		return;
+
+	/*
+	 * phys_to_virt doesn't work with hihgmem page but we could
+	 * call dma_mark_clean() with hihgmem page here. However, we
+	 * are fine since dma_mark_clean() is null on POWERPC. We can
+	 * make dma_mark_clean() take a physical address if necessary.
+	 */
+	dma_mark_clean(phys_to_virt(paddr), size);
+}
+
+void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
+			size_t size, enum dma_data_direction dir,
+			unsigned long attrs)
+{
+	unmap_single(hwdev, dev_addr, size, dir, attrs);
+}
+
+/*
+ * Make physical memory consistent for a single streaming mode DMA translation
+ * after a transfer.
+ *
+ * If you perform a swiotlb_map_page() but wish to interrogate the buffer
+ * using the cpu, yet do not wish to teardown the dma mapping, you must
+ * call this function before doing so.  At the next point you give the dma
+ * address back to the card, you must first perform a
+ * swiotlb_dma_sync_for_device, and then the device again owns the buffer
+ */
+static void
+swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
+		    size_t size, enum dma_data_direction dir,
+		    enum dma_sync_target target)
+{
+	phys_addr_t paddr = dma_to_phys(hwdev, dev_addr);
+
+	BUG_ON(dir == DMA_NONE);
+
+	if (is_swiotlb_buffer(paddr)) {
+		swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
+		return;
+	}
+
+	if (dir != DMA_FROM_DEVICE)
+		return;
+
+	dma_mark_clean(phys_to_virt(paddr), size);
+}
+
+void
+swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
+			    size_t size, enum dma_data_direction dir)
+{
+	swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
+}
+
+void
+swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
+			       size_t size, enum dma_data_direction dir)
+{
+	swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
+}
+
+/*
+ * Map a set of buffers described by scatterlist in streaming mode for DMA.
+ * This is the scatter-gather version of the above swiotlb_map_page
+ * 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_page are the
+ * same here.
+ */
+int
+swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
+		     enum dma_data_direction dir, unsigned long attrs)
+{
+	struct scatterlist *sg;
+	int i;
+
+	BUG_ON(dir == DMA_NONE);
+
+	for_each_sg(sgl, sg, nelems, i) {
+		phys_addr_t paddr = sg_phys(sg);
+		dma_addr_t dev_addr = phys_to_dma(hwdev, paddr);
+
+		if (swiotlb_force == SWIOTLB_FORCE ||
+		    !dma_capable(hwdev, dev_addr, sg->length)) {
+			phys_addr_t map = map_single(hwdev, sg_phys(sg),
+						     sg->length, dir, attrs);
+			if (map == SWIOTLB_MAP_ERROR) {
+				/* Don't panic here, we expect map_sg users
+				   to do proper error handling. */
+				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+				swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
+						       attrs);
+				sg_dma_len(sgl) = 0;
+				return 0;
+			}
+			sg->dma_address = __phys_to_dma(hwdev, map);
+		} else
+			sg->dma_address = dev_addr;
+		sg_dma_len(sg) = 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_page() above.
+ */
+void
+swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
+		       int nelems, enum dma_data_direction dir,
+		       unsigned long attrs)
+{
+	struct scatterlist *sg;
+	int i;
+
+	BUG_ON(dir == DMA_NONE);
+
+	for_each_sg(sgl, sg, nelems, i)
+		unmap_single(hwdev, sg->dma_address, sg_dma_len(sg), dir,
+			     attrs);
+}
+
+/*
+ * 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.
+ */
+static void
+swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
+		int nelems, enum dma_data_direction dir,
+		enum dma_sync_target target)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nelems, i)
+		swiotlb_sync_single(hwdev, sg->dma_address,
+				    sg_dma_len(sg), dir, target);
+}
+
+void
+swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
+			int nelems, enum dma_data_direction dir)
+{
+	swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
+}
+
+void
+swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+			   int nelems, enum dma_data_direction dir)
+{
+	swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
+}
+
+int
+swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
+{
+	return (dma_addr == __phys_to_dma(hwdev, io_tlb_overflow_buffer));
+}
+
+/*
+ * Return whether the given device DMA address mask can be supported
+ * properly.  For example, if your device can only drive the low 24-bits
+ * during bus mastering, then you would pass 0x00ffffff as the mask to
+ * this function.
+ */
+int
+swiotlb_dma_supported(struct device *hwdev, u64 mask)
+{
+	return __phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
+}
+
+void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
+		gfp_t gfp, unsigned long attrs)
+{
+	void *vaddr;
+
+	/* temporary workaround: */
+	if (gfp & __GFP_NOWARN)
+		attrs |= DMA_ATTR_NO_WARN;
+
+	/*
+	 * Don't print a warning when the first allocation attempt fails.
+	 * swiotlb_alloc_coherent() will print a warning when the DMA memory
+	 * allocation ultimately failed.
+	 */
+	gfp |= __GFP_NOWARN;
+
+	vaddr = dma_direct_alloc(dev, size, dma_handle, gfp, attrs);
+	if (!vaddr)
+		vaddr = swiotlb_alloc_buffer(dev, size, dma_handle, attrs);
+	return vaddr;
+}
+
+void swiotlb_free(struct device *dev, size_t size, void *vaddr,
+		dma_addr_t dma_addr, unsigned long attrs)
+{
+	if (!swiotlb_free_buffer(dev, size, dma_addr))
+		dma_direct_free(dev, size, vaddr, dma_addr, attrs);
+}
+
+const struct dma_map_ops swiotlb_dma_ops = {
+	.mapping_error		= swiotlb_dma_mapping_error,
+	.alloc			= swiotlb_alloc,
+	.free			= swiotlb_free,
+	.sync_single_for_cpu	= swiotlb_sync_single_for_cpu,
+	.sync_single_for_device	= swiotlb_sync_single_for_device,
+	.sync_sg_for_cpu	= swiotlb_sync_sg_for_cpu,
+	.sync_sg_for_device	= swiotlb_sync_sg_for_device,
+	.map_sg			= swiotlb_map_sg_attrs,
+	.unmap_sg		= swiotlb_unmap_sg_attrs,
+	.map_page		= swiotlb_map_page,
+	.unmap_page		= swiotlb_unmap_page,
+	.dma_supported		= dma_direct_supported,
+};
+EXPORT_SYMBOL(swiotlb_dma_ops);