/* SPDX-License-Identifier: GPL-2.0 */
  #include <linux/device.h>
  #include <linux/types.h>
  #include <linux/io.h>
  #include <linux/mm.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.

   * Moreover, 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 satisfied

  		 * 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_ioremap_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);