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-rw-r--r--include/asm-generic/io.h29
1 files changed, 8 insertions, 21 deletions
diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index bf8204de3a48..ed74d2e9af75 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -922,28 +922,16 @@ static inline void *phys_to_virt(unsigned long address)
/**
* DOC: ioremap() and ioremap_*() variants
*
- * If you have an IOMMU your architecture is expected to have both ioremap()
- * and iounmap() implemented otherwise the asm-generic helpers will provide a
- * direct mapping.
+ * Architectures with an MMU are expected to provide ioremap() and iounmap()
+ * themselves. For NOMMU architectures we provide a default nop-op
+ * implementation that expect that the physical address used for MMIO are
+ * already marked as uncached, and can be used as kernel virtual addresses.
*
- * There are ioremap_*() call variants, if you have no IOMMU we naturally will
- * default to direct mapping for all of them, you can override these defaults.
- * If you have an IOMMU you are highly encouraged to provide your own
- * ioremap variant implementation as there currently is no safe architecture
- * agnostic default. To avoid possible improper behaviour default asm-generic
- * ioremap_*() variants all return NULL when an IOMMU is available. If you've
- * defined your own ioremap_*() variant you must then declare your own
- * ioremap_*() variant as defined to itself to avoid the default NULL return.
+ * ioremap_wc() and ioremap_wt() can provide more relaxed caching attributes
+ * for specific drivers if the architecture choses to implement them. If they
+ * are not implemented we fall back to plain ioremap.
*/
#ifndef CONFIG_MMU
-
-/*
- * Change "struct page" to physical address.
- *
- * This implementation is for the no-MMU case only... if you have an MMU
- * you'll need to provide your own definitions.
- */
-
#ifndef ioremap
#define ioremap ioremap
static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
@@ -954,14 +942,13 @@ static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
#ifndef iounmap
#define iounmap iounmap
-
static inline void iounmap(void __iomem *addr)
{
}
#endif
#endif /* CONFIG_MMU */
+
#ifndef ioremap_nocache
-void __iomem *ioremap(phys_addr_t phys_addr, size_t size);
#define ioremap_nocache ioremap_nocache
static inline void __iomem *ioremap_nocache(phys_addr_t offset, size_t size)
{