On Sat, 17 Aug 2019, Christoph Hellwig wrote:
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@xxxxxx> --- 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(-)
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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
^^^ chooses - Paul
