/*
   * Copyright(c) 2015 Intel Corporation. All rights reserved.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of version 2 of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * 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.
   */

  #include <linux/radix-tree.h>

  #include <linux/device.h>

  #include <linux/types.h>

  #include <linux/pfn_t.h>

  #include <linux/io.h>
  #include <linux/mm.h>

  #include <linux/memory_hotplug.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>

  
  #ifndef ioremap_cache
  /* temporary while we convert existing ioremap_cache users to memremap */
  __weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
  {
  	return ioremap(offset, size);
  }
  #endif

  #ifndef arch_memremap_wb
  static void *arch_memremap_wb(resource_size_t offset, unsigned long size)
  {
  	return (__force void *)ioremap_cache(offset, size);
  }
  #endif

  #ifndef arch_memremap_can_ram_remap
  static bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
  					unsigned long flags)
  {
  	return true;
  }
  #endif
  
  static void *try_ram_remap(resource_size_t offset, size_t size,
  			   unsigned long flags)

  {

  	unsigned long pfn = PHYS_PFN(offset);

  
  	/* In the simple case just return the existing linear address */

  	if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)) &&
  	    arch_memremap_can_ram_remap(offset, size, flags))

  		return __va(offset);

  	return NULL; /* fallback to arch_memremap_wb */

  }

  /**
   * memremap() - remap an iomem_resource as cacheable memory
   * @offset: iomem resource start address
   * @size: size of remap

   * @flags: any of MEMREMAP_WB, MEMREMAP_WT, MEMREMAP_WC,
   *		  MEMREMAP_ENC, MEMREMAP_DEC

   *
   * memremap() is "ioremap" for cases where it is known that the resource
   * being mapped does not have i/o side effects and the __iomem

   * annotation is not applicable. In the case of multiple flags, the different
   * mapping types will be attempted in the order listed below until one of
   * them succeeds.

   *

   * MEMREMAP_WB - matches the default mapping for System RAM on

   * the architecture.  This is usually a read-allocate write-back cache.
   * Morever, if MEMREMAP_WB is specified and the requested remap region is RAM
   * memremap() will bypass establishing a new mapping and instead return
   * a pointer into the direct map.
   *
   * MEMREMAP_WT - establish a mapping whereby writes either bypass the
   * cache or are written through to memory and never exist in a
   * cache-dirty state with respect to program visibility.  Attempts to

   * map System RAM with this mapping type will fail.

   *
   * MEMREMAP_WC - establish a writecombine mapping, whereby writes may
   * be coalesced together (e.g. in the CPU's write buffers), but is otherwise
   * uncached. Attempts to map System RAM with this mapping type will fail.

   */
  void *memremap(resource_size_t offset, size_t size, unsigned long flags)
  {

  	int is_ram = region_intersects(offset, size,
  				       IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);

  	void *addr = NULL;

  	if (!flags)
  		return NULL;

  	if (is_ram == REGION_MIXED) {
  		WARN_ONCE(1, "memremap attempted on mixed range %pa size: %#lx
  ",
  				&offset, (unsigned long) size);
  		return NULL;
  	}
  
  	/* Try all mapping types requested until one returns non-NULL */
  	if (flags & MEMREMAP_WB) {

  		/*
  		 * MEMREMAP_WB is special in that it can be satisifed
  		 * from the direct map.  Some archs depend on the
  		 * capability of memremap() to autodetect cases where

  		 * the requested range is potentially in System RAM.

  		 */
  		if (is_ram == REGION_INTERSECTS)

  			addr = try_ram_remap(offset, size, flags);

  		if (!addr)

  			addr = arch_memremap_wb(offset, size);

  	}
  
  	/*

  	 * If we don't have a mapping yet and other request flags are
  	 * present then we will be attempting to establish a new virtual

  	 * address mapping.  Enforce that this mapping is not aliasing

  	 * System RAM.

  	 */

  	if (!addr && is_ram == REGION_INTERSECTS && flags != MEMREMAP_WB) {

  		WARN_ONCE(1, "memremap attempted on ram %pa size: %#lx
  ",
  				&offset, (unsigned long) size);
  		return NULL;
  	}

  	if (!addr && (flags & MEMREMAP_WT))

  		addr = ioremap_wt(offset, size);

  
  	if (!addr && (flags & MEMREMAP_WC))
  		addr = ioremap_wc(offset, size);

  
  	return addr;
  }
  EXPORT_SYMBOL(memremap);
  
  void memunmap(void *addr)
  {
  	if (is_vmalloc_addr(addr))
  		iounmap((void __iomem *) addr);
  }
  EXPORT_SYMBOL(memunmap);

  
  static void devm_memremap_release(struct device *dev, void *res)
  {

  	memunmap(*(void **)res);

  }
  
  static int devm_memremap_match(struct device *dev, void *res, void *match_data)
  {
  	return *(void **)res == match_data;
  }
  
  void *devm_memremap(struct device *dev, resource_size_t offset,
  		size_t size, unsigned long flags)
  {
  	void **ptr, *addr;

  	ptr = devres_alloc_node(devm_memremap_release, sizeof(*ptr), GFP_KERNEL,
  			dev_to_node(dev));

  	if (!ptr)

  		return ERR_PTR(-ENOMEM);

  
  	addr = memremap(offset, size, flags);
  	if (addr) {
  		*ptr = addr;
  		devres_add(dev, ptr);

  	} else {

  		devres_free(ptr);

  		return ERR_PTR(-ENXIO);
  	}

  
  	return addr;
  }
  EXPORT_SYMBOL(devm_memremap);
  
  void devm_memunmap(struct device *dev, void *addr)
  {

  	WARN_ON(devres_release(dev, devm_memremap_release,
  				devm_memremap_match, addr));

  }
  EXPORT_SYMBOL(devm_memunmap);

  
  #ifdef CONFIG_ZONE_DEVICE

  static DEFINE_MUTEX(pgmap_lock);
  static RADIX_TREE(pgmap_radix, GFP_KERNEL);
  #define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
  #define SECTION_SIZE (1UL << PA_SECTION_SHIFT)

  struct page_map {
  	struct resource res;

  	struct percpu_ref *ref;
  	struct dev_pagemap pgmap;

  	struct vmem_altmap altmap;

  };

  static unsigned long order_at(struct resource *res, unsigned long pgoff)

  {

  	unsigned long phys_pgoff = PHYS_PFN(res->start) + pgoff;
  	unsigned long nr_pages, mask;

  	nr_pages = PHYS_PFN(resource_size(res));
  	if (nr_pages == pgoff)
  		return ULONG_MAX;
  
  	/*
  	 * What is the largest aligned power-of-2 range available from
  	 * this resource pgoff to the end of the resource range,
  	 * considering the alignment of the current pgoff?
  	 */
  	mask = phys_pgoff | rounddown_pow_of_two(nr_pages - pgoff);
  	if (!mask)
  		return ULONG_MAX;
  
  	return find_first_bit(&mask, BITS_PER_LONG);
  }
  
  #define foreach_order_pgoff(res, order, pgoff) \
  	for (pgoff = 0, order = order_at((res), pgoff); order < ULONG_MAX; \
  			pgoff += 1UL << order, order = order_at((res), pgoff))

  #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
  int device_private_entry_fault(struct vm_area_struct *vma,
  		       unsigned long addr,
  		       swp_entry_t entry,
  		       unsigned int flags,
  		       pmd_t *pmdp)
  {
  	struct page *page = device_private_entry_to_page(entry);
  
  	/*
  	 * The page_fault() callback must migrate page back to system memory
  	 * so that CPU can access it. This might fail for various reasons
  	 * (device issue, device was unsafely unplugged, ...). When such
  	 * error conditions happen, the callback must return VM_FAULT_SIGBUS.
  	 *
  	 * Note that because memory cgroup charges are accounted to the device
  	 * memory, this should never fail because of memory restrictions (but
  	 * allocation of regular system page might still fail because we are
  	 * out of memory).
  	 *
  	 * There is a more in-depth description of what that callback can and
  	 * cannot do, in include/linux/memremap.h
  	 */
  	return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
  }
  EXPORT_SYMBOL(device_private_entry_fault);
  #endif /* CONFIG_DEVICE_PRIVATE */

  static void pgmap_radix_release(struct resource *res, unsigned long end_pgoff)

  {
  	unsigned long pgoff, order;

  
  	mutex_lock(&pgmap_lock);

  	foreach_order_pgoff(res, order, pgoff) {
  		if (pgoff >= end_pgoff)
  			break;

  		radix_tree_delete(&pgmap_radix, PHYS_PFN(res->start) + pgoff);

  	}

  	mutex_unlock(&pgmap_lock);

  
  	synchronize_rcu();

  }

  static unsigned long pfn_first(struct page_map *page_map)
  {
  	struct dev_pagemap *pgmap = &page_map->pgmap;
  	const struct resource *res = &page_map->res;
  	struct vmem_altmap *altmap = pgmap->altmap;
  	unsigned long pfn;
  
  	pfn = res->start >> PAGE_SHIFT;
  	if (altmap)
  		pfn += vmem_altmap_offset(altmap);
  	return pfn;
  }
  
  static unsigned long pfn_end(struct page_map *page_map)
  {
  	const struct resource *res = &page_map->res;
  
  	return (res->start + resource_size(res)) >> PAGE_SHIFT;
  }
  
  #define for_each_device_pfn(pfn, map) \
  	for (pfn = pfn_first(map); pfn < pfn_end(map); pfn++)

  static void devm_memremap_pages_release(struct device *dev, void *data)

  {

  	struct page_map *page_map = data;
  	struct resource *res = &page_map->res;
  	resource_size_t align_start, align_size;

  	struct dev_pagemap *pgmap = &page_map->pgmap;

  	unsigned long pfn;
  
  	for_each_device_pfn(pfn, page_map)
  		put_page(pfn_to_page(pfn));

  	if (percpu_ref_tryget_live(pgmap->ref)) {
  		dev_WARN(dev, "%s: page mapping is still live!
  ", __func__);
  		percpu_ref_put(pgmap->ref);
  	}

  	/* pages are dead and unused, undo the arch mapping */

  	align_start = res->start & ~(SECTION_SIZE - 1);

  	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
  		- align_start;

  	mem_hotplug_begin();

  	arch_remove_memory(align_start, align_size);

  	mem_hotplug_done();

  	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);

  	pgmap_radix_release(res, -1);

  	dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
  			"%s: failed to free all reserved pages
  ", __func__);

  }
  
  /* assumes rcu_read_lock() held at entry */
  struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
  {
  	struct page_map *page_map;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());

  	page_map = radix_tree_lookup(&pgmap_radix, PHYS_PFN(phys));

  	return page_map ? &page_map->pgmap : NULL;

  }

  /**
   * devm_memremap_pages - remap and provide memmap backing for the given resource
   * @dev: hosting device for @res
   * @res: "host memory" address range

   * @ref: a live per-cpu reference count

   * @altmap: optional descriptor for allocating the memmap from @res
   *

   * Notes:
   * 1/ @ref must be 'live' on entry and 'dead' before devm_memunmap_pages() time

   *    (or devm release event). The expected order of events is that @ref has
   *    been through percpu_ref_kill() before devm_memremap_pages_release(). The
   *    wait for the completion of all references being dropped and
   *    percpu_ref_exit() must occur after devm_memremap_pages_release().

   *
   * 2/ @res is expected to be a host memory range that could feasibly be
   *    treated as a "System RAM" range, i.e. not a device mmio range, but
   *    this is not enforced.

   */
  void *devm_memremap_pages(struct device *dev, struct resource *res,

  		struct percpu_ref *ref, struct vmem_altmap *altmap)

  {

  	resource_size_t align_start, align_size, align_end;
  	unsigned long pfn, pgoff, order;

  	pgprot_t pgprot = PAGE_KERNEL;

  	struct dev_pagemap *pgmap;

  	struct page_map *page_map;

  	int error, nid, is_ram, i = 0;

  	struct dev_pagemap *conflict_pgmap;

  
  	align_start = res->start & ~(SECTION_SIZE - 1);
  	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
  		- align_start;

  	align_end = align_start + align_size - 1;
  
  	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
  	if (conflict_pgmap) {
  		dev_WARN(dev, "Conflicting mapping in same section
  ");
  		put_dev_pagemap(conflict_pgmap);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
  	if (conflict_pgmap) {
  		dev_WARN(dev, "Conflicting mapping in same section
  ");
  		put_dev_pagemap(conflict_pgmap);
  		return ERR_PTR(-ENOMEM);
  	}

  	is_ram = region_intersects(align_start, align_size,
  		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);

  	if (is_ram != REGION_DISJOINT) {
  		WARN_ONCE(1, "%s attempted on %s region %pr
  ", __func__,
  				is_ram == REGION_MIXED ? "mixed" : "ram", res);

  		return ERR_PTR(-ENXIO);
  	}

  	if (!ref)
  		return ERR_PTR(-EINVAL);

  	page_map = devres_alloc_node(devm_memremap_pages_release,
  			sizeof(*page_map), GFP_KERNEL, dev_to_node(dev));

  	if (!page_map)
  		return ERR_PTR(-ENOMEM);

  	pgmap = &page_map->pgmap;

  
  	memcpy(&page_map->res, res, sizeof(*res));

  	pgmap->dev = dev;
  	if (altmap) {
  		memcpy(&page_map->altmap, altmap, sizeof(*altmap));
  		pgmap->altmap = &page_map->altmap;
  	}

  	pgmap->ref = ref;

  	pgmap->res = &page_map->res;

  	pgmap->type = MEMORY_DEVICE_HOST;
  	pgmap->page_fault = NULL;
  	pgmap->page_free = NULL;
  	pgmap->data = NULL;

  	mutex_lock(&pgmap_lock);
  	error = 0;

  
  	foreach_order_pgoff(res, order, pgoff) {

  		struct dev_pagemap *dup;
  
  		rcu_read_lock();

  		dup = find_dev_pagemap(res->start + PFN_PHYS(pgoff));

  		rcu_read_unlock();
  		if (dup) {
  			dev_err(dev, "%s: %pr collides with mapping for %s
  ",
  					__func__, res, dev_name(dup->dev));
  			error = -EBUSY;
  			break;
  		}

  		error = __radix_tree_insert(&pgmap_radix,
  				PHYS_PFN(res->start) + pgoff, order, page_map);

  		if (error) {
  			dev_err(dev, "%s: failed: %d
  ", __func__, error);
  			break;
  		}
  	}
  	mutex_unlock(&pgmap_lock);
  	if (error)
  		goto err_radix;

  	nid = dev_to_node(dev);
  	if (nid < 0)

  		nid = numa_mem_id();

  	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
  			align_size);
  	if (error)
  		goto err_pfn_remap;

  	mem_hotplug_begin();

  	error = arch_add_memory(nid, align_start, align_size, false);

  	if (!error)
  		move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
  					align_start >> PAGE_SHIFT,
  					align_size >> PAGE_SHIFT);

  	mem_hotplug_done();

  	if (error)
  		goto err_add_memory;

  	for_each_device_pfn(pfn, page_map) {
  		struct page *page = pfn_to_page(pfn);

  		/*
  		 * ZONE_DEVICE pages union ->lru with a ->pgmap back
  		 * pointer.  It is a bug if a ZONE_DEVICE page is ever
  		 * freed or placed on a driver-private list.  Seed the
  		 * storage with LIST_POISON* values.
  		 */
  		list_del(&page->lru);

  		page->pgmap = pgmap;

  		percpu_ref_get(ref);

  		if (!(++i % 1024))
  			cond_resched();

  	}

  	devres_add(dev, page_map);
  	return __va(res->start);

  
   err_add_memory:

  	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
   err_pfn_remap:

   err_radix:

  	pgmap_radix_release(res, pgoff);

  	devres_free(page_map);
  	return ERR_PTR(error);

  }

  EXPORT_SYMBOL_GPL(devm_memremap_pages);

  
  unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
  {
  	/* number of pfns from base where pfn_to_page() is valid */
  	return altmap->reserve + altmap->free;
  }
  
  void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
  {
  	altmap->alloc -= nr_pfns;
  }

  struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
  {
  	/*
  	 * 'memmap_start' is the virtual address for the first "struct
  	 * page" in this range of the vmemmap array.  In the case of

  	 * CONFIG_SPARSEMEM_VMEMMAP a page_to_pfn conversion is simple

  	 * pointer arithmetic, so we can perform this to_vmem_altmap()
  	 * conversion without concern for the initialization state of
  	 * the struct page fields.
  	 */
  	struct page *page = (struct page *) memmap_start;
  	struct dev_pagemap *pgmap;
  
  	/*

  	 * Unconditionally retrieve a dev_pagemap associated with the

  	 * given physical address, this is only for use in the
  	 * arch_{add|remove}_memory() for setting up and tearing down
  	 * the memmap.
  	 */
  	rcu_read_lock();
  	pgmap = find_dev_pagemap(__pfn_to_phys(page_to_pfn(page)));
  	rcu_read_unlock();
  
  	return pgmap ? pgmap->altmap : NULL;
  }

  #endif /* CONFIG_ZONE_DEVICE */

  #if IS_ENABLED(CONFIG_DEVICE_PRIVATE) ||  IS_ENABLED(CONFIG_DEVICE_PUBLIC)
  void put_zone_device_private_or_public_page(struct page *page)

  {
  	int count = page_ref_dec_return(page);
  
  	/*
  	 * If refcount is 1 then page is freed and refcount is stable as nobody
  	 * holds a reference on the page.
  	 */
  	if (count == 1) {
  		/* Clear Active bit in case of parallel mark_page_accessed */
  		__ClearPageActive(page);
  		__ClearPageWaiters(page);
  
  		page->mapping = NULL;

  		mem_cgroup_uncharge(page);

  
  		page->pgmap->page_free(page, page->pgmap->data);
  	} else if (!count)
  		__put_page(page);
  }

  EXPORT_SYMBOL(put_zone_device_private_or_public_page);
  #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */