[PATCH 3/6] dma-mapping: remove arch_dma_mmap_pgprot

Paul Burton paul.burton at mips.com
Tue Aug 27 20:02:51 AEST 2019


Hi Christoph,

On Mon, Aug 26, 2019 at 03:25:50PM +0200, Christoph Hellwig wrote:
> arch_dma_mmap_pgprot is used for two things:
> 
>  1) to override the "normal" uncached page attributes for mapping
>     memory coherent to devices that can't snoop the CPU caches
>  2) to provide the special DMA_ATTR_WRITE_COMBINE semantics on older
>     arm systems and some mips platforms
> 
> Replace one with the pgprot_dmacoherent macro that is already provided
> by arm and much simpler to use, and lift the DMA_ATTR_WRITE_COMBINE
> handling to common code with an explicit arch opt-in.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> Acked-by: Geert Uytterhoeven <geert at linux-m68k.org>

For the MIPS bits:

    Acked-by: Paul Burton <paul.burton at mips.com>

Thanks,
    Paul

> ---
>  arch/arm/Kconfig                   |  2 +-
>  arch/arm/mm/dma-mapping.c          |  6 ------
>  arch/arm64/Kconfig                 |  1 -
>  arch/arm64/include/asm/pgtable.h   |  4 ++++
>  arch/arm64/mm/dma-mapping.c        |  6 ------
>  arch/m68k/Kconfig                  |  1 -
>  arch/m68k/include/asm/pgtable_mm.h |  3 +++
>  arch/m68k/kernel/dma.c             |  3 +--
>  arch/mips/Kconfig                  |  2 +-
>  arch/mips/mm/dma-noncoherent.c     |  8 --------
>  include/linux/dma-noncoherent.h    | 13 +++++++++++--
>  kernel/dma/Kconfig                 | 12 +++++++++---
>  kernel/dma/mapping.c               |  8 +++++---
>  13 files changed, 35 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 24360211534a..217083caeabd 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -8,7 +8,7 @@ config ARM
>  	select ARCH_HAS_DEBUG_VIRTUAL if MMU
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_HAS_DMA_COHERENT_TO_PFN if SWIOTLB
> -	select ARCH_HAS_DMA_MMAP_PGPROT if SWIOTLB
> +	select ARCH_HAS_DMA_WRITE_COMBINE if !ARM_DMA_MEM_BUFFERABLE
>  	select ARCH_HAS_ELF_RANDOMIZE
>  	select ARCH_HAS_FORTIFY_SOURCE
>  	select ARCH_HAS_KEEPINITRD
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index d42557ee69c2..d27b12f61737 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2402,12 +2402,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
>  	return dma_to_pfn(dev, dma_addr);
>  }
>  
> -pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> -		unsigned long attrs)
> -{
> -	return __get_dma_pgprot(attrs, prot);
> -}
> -
>  void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  		gfp_t gfp, unsigned long attrs)
>  {
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 3adcec05b1f6..dab9dda34206 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -13,7 +13,6 @@ config ARM64
>  	select ARCH_HAS_DEBUG_VIRTUAL
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_HAS_DMA_COHERENT_TO_PFN
> -	select ARCH_HAS_DMA_MMAP_PGPROT
>  	select ARCH_HAS_DMA_PREP_COHERENT
>  	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
>  	select ARCH_HAS_ELF_RANDOMIZE
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index e09760ece844..6700371227d1 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -435,6 +435,10 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>  	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_NC) | PTE_PXN | PTE_UXN)
>  #define pgprot_device(prot) \
>  	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_PXN | PTE_UXN)
> +#define pgprot_dmacoherent(prot) \
> +	__pgprot_modify(prot, PTE_ATTRINDX_MASK, \
> +			PTE_ATTRINDX(MT_NORMAL_NC) | PTE_PXN | PTE_UXN)
> +
>  #define __HAVE_PHYS_MEM_ACCESS_PROT
>  struct file;
>  extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index bd2b039f43a6..676efcda51e6 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -11,12 +11,6 @@
>  
>  #include <asm/cacheflush.h>
>  
> -pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> -		unsigned long attrs)
> -{
> -	return pgprot_writecombine(prot);
> -}
> -
>  void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
>  		size_t size, enum dma_data_direction dir)
>  {
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index c518d695c376..a9e564306d3e 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -4,7 +4,6 @@ config M68K
>  	default y
>  	select ARCH_32BIT_OFF_T
>  	select ARCH_HAS_BINFMT_FLAT
> -	select ARCH_HAS_DMA_MMAP_PGPROT if MMU && !COLDFIRE
>  	select ARCH_HAS_DMA_PREP_COHERENT if HAS_DMA && MMU && !COLDFIRE
>  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
>  	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
> diff --git a/arch/m68k/include/asm/pgtable_mm.h b/arch/m68k/include/asm/pgtable_mm.h
> index fe3ddd73a0cc..fde4534b974f 100644
> --- a/arch/m68k/include/asm/pgtable_mm.h
> +++ b/arch/m68k/include/asm/pgtable_mm.h
> @@ -169,6 +169,9 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
>  	    ? (__pgprot((pgprot_val(prot) & _CACHEMASK040) | _PAGE_NOCACHE_S))	\
>  	    : (prot)))
>  
> +pgprot_t pgprot_dmacoherent(pgprot_t prot);
> +#define pgprot_dmacoherent(prot)	pgprot_dmacoherent(prot)
> +
>  #endif /* CONFIG_COLDFIRE */
>  #include <asm-generic/pgtable.h>
>  #endif /* !__ASSEMBLY__ */
> diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
> index 30cd59caf037..35064150e348 100644
> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -23,8 +23,7 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
>  	cache_push(page_to_phys(page), size);
>  }
>  
> -pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> -		unsigned long attrs)
> +pgprot_t pgprot_dmacoherent(pgprot_t prot)
>  {
>  	if (CPU_IS_040_OR_060) {
>  		pgprot_val(prot) &= ~_PAGE_CACHE040;
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index d50fafd7bf3a..fc88f68ea1ee 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -1119,7 +1119,7 @@ config DMA_PERDEV_COHERENT
>  
>  config DMA_NONCOHERENT
>  	bool
> -	select ARCH_HAS_DMA_MMAP_PGPROT
> +	select ARCH_HAS_DMA_WRITE_COMBINE
>  	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
>  	select ARCH_HAS_UNCACHED_SEGMENT
>  	select NEED_DMA_MAP_STATE
> diff --git a/arch/mips/mm/dma-noncoherent.c b/arch/mips/mm/dma-noncoherent.c
> index ed56c6fa7be2..1d4d57dd9acf 100644
> --- a/arch/mips/mm/dma-noncoherent.c
> +++ b/arch/mips/mm/dma-noncoherent.c
> @@ -65,14 +65,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
>  	return page_to_pfn(virt_to_page(cached_kernel_address(cpu_addr)));
>  }
>  
> -pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> -		unsigned long attrs)
> -{
> -	if (attrs & DMA_ATTR_WRITE_COMBINE)
> -		return pgprot_writecombine(prot);
> -	return pgprot_noncached(prot);
> -}
> -
>  static inline void dma_sync_virt(void *addr, size_t size,
>  		enum dma_data_direction dir)
>  {
> diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h
> index 0bff3d7fac92..dd3de6d88fc0 100644
> --- a/include/linux/dma-noncoherent.h
> +++ b/include/linux/dma-noncoherent.h
> @@ -3,6 +3,7 @@
>  #define _LINUX_DMA_NONCOHERENT_H 1
>  
>  #include <linux/dma-mapping.h>
> +#include <asm/pgtable.h>
>  
>  #ifdef CONFIG_ARCH_HAS_DMA_COHERENCE_H
>  #include <asm/dma-coherence.h>
> @@ -42,10 +43,18 @@ void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,
>  		dma_addr_t dma_addr, unsigned long attrs);
>  long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
>  		dma_addr_t dma_addr);
> -pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> -		unsigned long attrs);
>  
>  #ifdef CONFIG_MMU
> +/*
> + * Page protection so that devices that can't snoop CPU caches can use the
> + * memory coherently.  We default to pgprot_noncached which is usually used
> + * for ioremap as a safe bet, but architectures can override this with less
> + * strict semantics if possible.
> + */
> +#ifndef pgprot_dmacoherent
> +#define pgprot_dmacoherent(prot)	pgprot_noncached(prot)
> +#endif
> +
>  pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs);
>  #else
>  static inline pgprot_t dma_pgprot(struct device *dev, pgprot_t prot,
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index 9decbba255fc..73c5c2b8e824 100644
> --- a/kernel/dma/Kconfig
> +++ b/kernel/dma/Kconfig
> @@ -20,6 +20,15 @@ config ARCH_HAS_DMA_COHERENCE_H
>  config ARCH_HAS_DMA_SET_MASK
>  	bool
>  
> +#
> +# Select this option if the architecture needs special handling for
> +# DMA_ATTR_WRITE_COMBINE.  Normally the "uncached" mapping should be what
> +# people thing of when saying write combine, so very few platforms should
> +# need to enable this.
> +#
> +config ARCH_HAS_DMA_WRITE_COMBINE
> +	bool
> +
>  config DMA_DECLARE_COHERENT
>  	bool
>  
> @@ -45,9 +54,6 @@ config ARCH_HAS_DMA_PREP_COHERENT
>  config ARCH_HAS_DMA_COHERENT_TO_PFN
>  	bool
>  
> -config ARCH_HAS_DMA_MMAP_PGPROT
> -	bool
> -
>  config ARCH_HAS_FORCE_DMA_UNENCRYPTED
>  	bool
>  
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index b0038ca3aa92..1b96616c9f20 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -161,9 +161,11 @@ pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs)
>  	    (IS_ENABLED(CONFIG_DMA_NONCOHERENT_CACHE_SYNC) &&
>               (attrs & DMA_ATTR_NON_CONSISTENT)))
>  		return prot;
> -	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_MMAP_PGPROT))
> -		return arch_dma_mmap_pgprot(dev, prot, attrs);
> -	return pgprot_noncached(prot);
> +#ifdef CONFIG_ARCH_HAS_DMA_WRITE_COMBINE
> +	if (attrs & DMA_ATTR_WRITE_COMBINE)
> +		return pgprot_writecombine(prot);
> +#endif
> +	return pgprot_dmacoherent(prot);
>  }
>  #endif /* CONFIG_MMU */
>  
> -- 
> 2.20.1
> 


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