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asm-generic: don't provide ioremap for CONFIG_MMU

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All MMU-enabled ports have a non-trivial ioremap and should thus provide
the prototype for their implementation instead of providing a generic
one unless a different symbol is not defined.  Note that this only
affects sparc32 nds32 as all others do provide their own version.

Also update the kerneldoc comments in asm-generic/io.h to explain the
situation around the default ioremap* implementations correctly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Christoph Hellwig
2019-08-11 14:53:20 +02:00
parent e97133959a
commit 97c9801a15
3 changed files with 11 additions and 21 deletions
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29
include/asm-generic/io.h
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@@ -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)
{