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    Subject[PATCH 11/21] asm-generic: don't provide ioremap for CONFIG_MMU
    Date
    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>
    ---
    arch/nds32/include/asm/io.h | 2 ++
    arch/sparc/include/asm/io_32.h | 1 +
    include/asm-generic/io.h | 29 ++++++++---------------------
    3 files changed, 11 insertions(+), 21 deletions(-)

    diff --git a/arch/nds32/include/asm/io.h b/arch/nds32/include/asm/io.h
    index 16f262322b8f..fb0e8a24c7af 100644
    --- a/arch/nds32/include/asm/io.h
    +++ b/arch/nds32/include/asm/io.h
    @@ -6,6 +6,7 @@

    #include <linux/types.h>

    +void __iomem *ioremap(phys_addr_t phys_addr, size_t size);
    extern void iounmap(volatile void __iomem *addr);
    #define __raw_writeb __raw_writeb
    static inline void __raw_writeb(u8 val, volatile void __iomem *addr)
    @@ -80,4 +81,5 @@ static inline u32 __raw_readl(const volatile void __iomem *addr)
    #define writew(v,c) ({ __iowmb(); writew_relaxed((v),(c)); })
    #define writel(v,c) ({ __iowmb(); writel_relaxed((v),(c)); })
    #include <asm-generic/io.h>
    +
    #endif /* __ASM_NDS32_IO_H */
    diff --git a/arch/sparc/include/asm/io_32.h b/arch/sparc/include/asm/io_32.h
    index df2dc1784673..9a52d9506f80 100644
    --- a/arch/sparc/include/asm/io_32.h
    +++ b/arch/sparc/include/asm/io_32.h
    @@ -127,6 +127,7 @@ static inline void sbus_memcpy_toio(volatile void __iomem *dst,
    * Bus number may be embedded in the higher bits of the physical address.
    * This is why we have no bus number argument to ioremap().
    */
    +void __iomem *ioremap(phys_addr_t offset, size_t size);
    void iounmap(volatile void __iomem *addr);
    /* Create a virtual mapping cookie for an IO port range */
    void __iomem *ioport_map(unsigned long port, unsigned int nr);
    diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
    index a98ed6325727..6a5edc23afe2 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)
    {
    --
    2.20.1
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