v4.19.13 snapshot.
diff --git a/kernel/iomem.c b/kernel/iomem.c
new file mode 100644
index 0000000..f7525e1
--- /dev/null
+++ b/kernel/iomem.c
@@ -0,0 +1,167 @@
+/* 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.
+ * 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\n",
+ &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\n",
+ &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);