linux-kernel - Re: [PATCH 17/21] lib: provide a simple generic ioremap implementation

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Date:   Thu, 07 Nov 2019 07:29:10 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Christoph Hellwig <hch@....de>
CC:     Arnd Bergmann <arnd@...db.de>, guoren@...nel.org, monstr@...str.eu,
        green.hu@...il.com, deanbo422@...il.com, gxt@....edu.cn,
        x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        nios2-dev@...ts.rocketboards.org, openrisc@...ts.librecores.org,
        linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        linux-mtd@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject:     Re: [PATCH 17/21] lib: provide a simple generic ioremap implementation

On Mon, 28 Oct 2019 23:48:30 PDT (-0700), Christoph Hellwig wrote:
> A lot of architectures reuse the same simple ioremap implementation, so
> start lifting the most simple variant to lib/ioremap.c.  It provides
> ioremap_prot and iounmap, plus a default ioremap that uses prot_noncached,
> although that can be overridden by asm/io.h.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  include/asm-generic/io.h | 20 ++++++++++++++++----
>  lib/Kconfig              |  3 +++
>  lib/ioremap.c            | 39 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 58 insertions(+), 4 deletions(-)
>
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 4e45e1cb6560..4a661fdd1937 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -923,9 +923,10 @@ static inline void *phys_to_virt(unsigned long address)
>   * DOC: ioremap() and ioremap_*() variants
>   *
>   * 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.
> + * themselves or rely on GENERIC_IOREMAP.  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.
>   *
>   * ioremap_wc() and ioremap_wt() can provide more relaxed caching attributes
>   * for specific drivers if the architecture choses to implement them.  If they
> @@ -946,7 +947,18 @@ static inline void iounmap(void __iomem *addr)
>  {
>  }
>  #endif
> -#endif /* CONFIG_MMU */
> +#elif defined(CONFIG_GENERIC_IOREMAP)
> +#include <asm/pgtable.h>
> +
> +void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot);
> +void iounmap(volatile void __iomem *addr);
> +
> +static inline void __iomem *ioremap(phys_addr_t addr, size_t size)
> +{
> +	/* _PAGE_IOREMAP needs to be supplied by the architecture */
> +	return ioremap_prot(addr, size, _PAGE_IOREMAP);
> +}
> +#endif /* !CONFIG_MMU || CONFIG_GENERIC_IOREMAP */
>
>  #ifndef ioremap_nocache
>  #define ioremap_nocache ioremap
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 183f92a297ca..afc78aaf2b25 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -638,6 +638,9 @@ config STRING_SELFTEST
>
>  endmenu
>
> +config GENERIC_IOREMAP
> +	bool
> +
>  config GENERIC_LIB_ASHLDI3
>  	bool
>
> diff --git a/lib/ioremap.c b/lib/ioremap.c
> index 0a2ffadc6d71..3f0e18543de8 100644
> --- a/lib/ioremap.c
> +++ b/lib/ioremap.c
> @@ -231,3 +231,42 @@ int ioremap_page_range(unsigned long addr,
>
>  	return err;
>  }
> +
> +#ifdef CONFIG_GENERIC_IOREMAP
> +void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot)
> +{
> +	unsigned long offset, vaddr;
> +	phys_addr_t last_addr;
> +	struct vm_struct *area;
> +
> +	/* Disallow wrap-around or zero size */
> +	last_addr = addr + size - 1;
> +	if (!size || last_addr < addr)
> +		return NULL;
> +
> +	/* Page-align mappings */
> +	offset = addr & (~PAGE_MASK);
> +	addr -= offset;
> +	size = PAGE_ALIGN(size + offset);
> +
> +	area = get_vm_area_caller(size, VM_IOREMAP,
> +			__builtin_return_address(0));
> +	if (!area)
> +		return NULL;
> +	vaddr = (unsigned long)area->addr;
> +
> +	if (ioremap_page_range(vaddr, vaddr + size, addr, __pgprot(prot))) {
> +		free_vm_area(area);
> +		return NULL;
> +	}
> +
> +	return (void __iomem *)(vaddr + offset);
> +}
> +EXPORT_SYMBOL(ioremap_prot);
> +
> +void iounmap(volatile void __iomem *addr)
> +{
> +	vunmap((void *)((unsigned long)addr & PAGE_MASK));
> +}
> +EXPORT_SYMBOL(iounmap);
> +#endif /* CONFIG_GENERIC_IOREMAP */

Reviewed-by: Palmer Dabbelt <palmer@...belt.com>

Thanks!  This should let us get rid of arch/riscv/mm/ioremap.c.