On Mon, 28 Oct 2019 23:48:23 PDT (-0700), Christoph Hellwig wrote:
> Whatever reason there is for the existence of ioremap_uc, and the fact
> that it returns NULL by default on architectures with an MMU applies
> equally to nommu architectures, so don't provide different defaults.
>
> In practice the difference is meaningless as the only portable driver
> that uses ioremap_uc is atyfb which probably doesn't show up on nommu
> devices.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> include/asm-generic/io.h | 36 ++++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 20 deletions(-)
>
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index d02806513670..a98ed6325727 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -935,18 +935,7 @@ static inline void *phys_to_virt(unsigned long address)
> * defined your own ioremap_*() variant you must then declare your own
> * ioremap_*() variant as defined to itself to avoid the default NULL return.
> */
> -
> -#ifdef CONFIG_MMU
> -
> -#ifndef ioremap_uc
> -#define ioremap_uc ioremap_uc
> -static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
> -{
> - return NULL;
> -}
> -#endif
> -
> -#else /* !CONFIG_MMU */
> +#ifndef CONFIG_MMU
>
> /*
> * Change "struct page" to physical address.
> @@ -980,14 +969,6 @@ static inline void __iomem *ioremap_nocache(phys_addr_t offset, size_t size)
> }
> #endif
>
> -#ifndef ioremap_uc
> -#define ioremap_uc ioremap_uc
> -static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
> -{
> - return ioremap_nocache(offset, size);
> -}
> -#endif
> -
> #ifndef ioremap_wc
> #define ioremap_wc ioremap_wc
> static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
> @@ -1004,6 +985,21 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
> }
> #endif
>
> +/*
> + * ioremap_uc is special in that we do require an explicit architecture
> + * implementation. In general you do now want to use this function in a
Presumably that's supposed to be "do not want to use"?
> + * driver and use plain ioremap, which is uncached by default. Similarly
> + * architectures should not implement it unless they have a very good
> + * reason.
> + */
> +#ifndef ioremap_uc
> +#define ioremap_uc ioremap_uc
> +static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
> +{
> + return NULL;
> +}
> +#endif
> +
> #ifdef CONFIG_HAS_IOPORT_MAP
> #ifndef CONFIG_GENERIC_IOMAP
> #ifndef ioport_map
With the fix:
Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxx>
