arm64: allow ioremap_cache() to use existing RAM mappings

Some drivers (ACPI notably) use ioremap_cache() to map an area which could
either be outside of kernel RAM or in an already mapped reserved area of
RAM. To avoid aliases with different caching attributes, ioremap() does
not allow RAM to be remapped. But for ioremap_cache(), the existing kernel
mapping may be used.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index 1725cd6db37a..2bb1d586664c 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -77,8 +77,24 @@ EXPORT_SYMBOL(__ioremap);
 
 void __iounmap(volatile void __iomem *io_addr)
 {
-	void *addr = (void *)(PAGE_MASK & (unsigned long)io_addr);
+	unsigned long addr = (unsigned long)io_addr & PAGE_MASK;
 
-	vunmap(addr);
+	/*
+	 * We could get an address outside vmalloc range in case
+	 * of ioremap_cache() reusing a RAM mapping.
+	 */
+	if (VMALLOC_START <= addr && addr < VMALLOC_END)
+		vunmap((void *)addr);
 }
 EXPORT_SYMBOL(__iounmap);
+
+void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size)
+{
+	/* For normal memory we already have a cacheable mapping. */
+	if (pfn_valid(__phys_to_pfn(phys_addr)))
+		return (void __iomem *)__phys_to_virt(phys_addr);
+
+	return __ioremap_caller(phys_addr, size, __pgprot(PROT_NORMAL),
+				__builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_cache);