Re: [PATCH 15/15] dma-mapping: bypass indirect calls for dma-direct

From: Marek Szyprowski
Date: Fri Dec 14 2018 - 09:11:46 EST

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Hi Christoph,

On 2018-12-07 20:07, Christoph Hellwig wrote:
> Avoid expensive indirect calls in the fast path DMA mapping
> operations by directly calling the dma_direct_* ops if we are using
> the directly mapped DMA operations.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

This breaks direct DMA on ARM64 (also todays linux-next). NULL
dev->dma_ops fallbacks to get_arch_dma_ops(), which in turn returns
non-functional &dma_dummy_ops on ARM64...

> ---
> arch/alpha/include/asm/dma-mapping.h | 2 +-
> arch/arc/mm/cache.c | 2 +-
> arch/arm/include/asm/dma-mapping.h | 2 +-
> arch/arm/mm/dma-mapping-nommu.c | 14 +---
> arch/arm64/mm/dma-mapping.c | 3 -
> arch/ia64/hp/common/hwsw_iommu.c | 2 +-
> arch/ia64/hp/common/sba_iommu.c | 4 +-
> arch/ia64/kernel/dma-mapping.c | 1 -
> arch/mips/include/asm/dma-mapping.h | 2 +-
> arch/parisc/kernel/setup.c | 4 -
> arch/sparc/include/asm/dma-mapping.h | 4 +-
> arch/x86/kernel/pci-dma.c | 2 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +-
> drivers/iommu/amd_iommu.c | 13 +---
> include/asm-generic/dma-mapping.h | 2 +-
> include/linux/dma-direct.h | 17 ----
> include/linux/dma-mapping.h | 111 +++++++++++++++++++++++----
> include/linux/dma-noncoherent.h | 5 +-
> kernel/dma/direct.c | 37 ++-------
> kernel/dma/mapping.c | 40 ++++++----
> 20 files changed, 150 insertions(+), 119 deletions(-)
>
> diff --git a/arch/alpha/include/asm/dma-mapping.h b/arch/alpha/include/asm/dma-mapping.h
> index 8beeafd4f68e..0ee6a5c99b16 100644
> --- a/arch/alpha/include/asm/dma-mapping.h
> +++ b/arch/alpha/include/asm/dma-mapping.h
> @@ -7,7 +7,7 @@ extern const struct dma_map_ops alpha_pci_ops;
> static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> {
> #ifdef CONFIG_ALPHA_JENSEN
> - return &dma_direct_ops;
> + return NULL;
> #else
> return &alpha_pci_ops;
> #endif
> diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
> index f2701c13a66b..e188bb3ede53 100644
> --- a/arch/arc/mm/cache.c
> +++ b/arch/arc/mm/cache.c
> @@ -1280,7 +1280,7 @@ void __init arc_cache_init_master(void)
> /*
> * In case of IOC (say IOC+SLC case), pointers above could still be set
> * but end up not being relevant as the first function in chain is not
> - * called at all for @dma_direct_ops
> + * called at all for devices using coherent DMA.
> * arch_sync_dma_for_cpu() -> dma_cache_*() -> __dma_cache_*()
> */
> }
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index 965b7c846ecb..31d3b96f0f4b 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -18,7 +18,7 @@ extern const struct dma_map_ops arm_coherent_dma_ops;
>
> static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> {
> - return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_direct_ops;
> + return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : NULL;
> }
>
> #ifdef __arch_page_to_dma
> diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
> index 712416ecd8e6..f304b10e23a4 100644
> --- a/arch/arm/mm/dma-mapping-nommu.c
> +++ b/arch/arm/mm/dma-mapping-nommu.c
> @@ -22,7 +22,7 @@
> #include "dma.h"
>
> /*
> - * dma_direct_ops is used if
> + * The generic direct mapping code is used if
> * - MMU/MPU is off
> * - cpu is v7m w/o cache support
> * - device is coherent
> @@ -209,16 +209,9 @@ const struct dma_map_ops arm_nommu_dma_ops = {
> };
> EXPORT_SYMBOL(arm_nommu_dma_ops);
>
> -static const struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)
> -{
> - return coherent ? &dma_direct_ops : &arm_nommu_dma_ops;
> -}
> -
> void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> const struct iommu_ops *iommu, bool coherent)
> {
> - const struct dma_map_ops *dma_ops;
> -
> if (IS_ENABLED(CONFIG_CPU_V7M)) {
> /*
> * Cache support for v7m is optional, so can be treated as
> @@ -234,7 +227,6 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
> }
>
> - dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);
> -
> - set_dma_ops(dev, dma_ops);
> + if (!dev->archdata.dma_coherent)
> + set_dma_ops(dev, &arm_nommu_dma_ops);
> }
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index ab1e417204d0..95eda81e3f2d 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -462,9 +462,6 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> const struct iommu_ops *iommu, bool coherent)
> {
> - if (!dev->dma_ops)
> - dev->dma_ops = &dma_direct_ops;
> -
> dev->dma_coherent = coherent;
> __iommu_setup_dma_ops(dev, dma_base, size, iommu);
>
> diff --git a/arch/ia64/hp/common/hwsw_iommu.c b/arch/ia64/hp/common/hwsw_iommu.c
> index f40ca499b246..8840ed97712f 100644
> --- a/arch/ia64/hp/common/hwsw_iommu.c
> +++ b/arch/ia64/hp/common/hwsw_iommu.c
> @@ -38,7 +38,7 @@ static inline int use_swiotlb(struct device *dev)
> const struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
> {
> if (use_swiotlb(dev))
> - return &dma_direct_ops;
> + return NULL;
> return &sba_dma_ops;
> }
> EXPORT_SYMBOL(hwsw_dma_get_ops);
> diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
> index 5ee74820a0f6..5a361e51cb1e 100644
> --- a/arch/ia64/hp/common/sba_iommu.c
> +++ b/arch/ia64/hp/common/sba_iommu.c
> @@ -2078,7 +2078,7 @@ sba_init(void)
> * a successful kdump kernel boot is to use the swiotlb.
> */
> if (is_kdump_kernel()) {
> - dma_ops = &dma_direct_ops;
> + dma_ops = NULL;
> if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
> panic("Unable to initialize software I/O TLB:"
> " Try machvec=dig boot option");
> @@ -2100,7 +2100,7 @@ sba_init(void)
> * If we didn't find something sba_iommu can claim, we
> * need to setup the swiotlb and switch to the dig machvec.
> */
> - dma_ops = &dma_direct_ops;
> + dma_ops = NULL;
> if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
> panic("Unable to find SBA IOMMU or initialize "
> "software I/O TLB: Try machvec=dig boot option");
> diff --git a/arch/ia64/kernel/dma-mapping.c b/arch/ia64/kernel/dma-mapping.c
> index 80cd3e1ea95a..ad7d9963de34 100644
> --- a/arch/ia64/kernel/dma-mapping.c
> +++ b/arch/ia64/kernel/dma-mapping.c
> @@ -36,7 +36,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
>
> void __init swiotlb_dma_init(void)
> {
> - dma_ops = &dma_direct_ops;
> swiotlb_init(1);
> }
> #endif
> diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h
> index 69f914667f3e..20dfaad3a55d 100644
> --- a/arch/mips/include/asm/dma-mapping.h
> +++ b/arch/mips/include/asm/dma-mapping.h
> @@ -11,7 +11,7 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> #if defined(CONFIG_MACH_JAZZ)
> return &jazz_dma_ops;
> #else
> - return &dma_direct_ops;
> + return NULL;
> #endif
> }
>
> diff --git a/arch/parisc/kernel/setup.c b/arch/parisc/kernel/setup.c
> index cd227f1cf629..54818cd78bd0 100644
> --- a/arch/parisc/kernel/setup.c
> +++ b/arch/parisc/kernel/setup.c
> @@ -99,10 +99,6 @@ void __init dma_ops_init(void)
>
> case pcxl2:
> pa7300lc_init();
> - case pcxl: /* falls through */
> - case pcxs:
> - case pcxt:
> - hppa_dma_ops = &dma_direct_ops;
> break;
> default:
> break;
> diff --git a/arch/sparc/include/asm/dma-mapping.h b/arch/sparc/include/asm/dma-mapping.h
> index b0bb2fcaf1c9..59f5a0f17316 100644
> --- a/arch/sparc/include/asm/dma-mapping.h
> +++ b/arch/sparc/include/asm/dma-mapping.h
> @@ -14,11 +14,11 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> {
> #ifdef CONFIG_SPARC_LEON
> if (sparc_cpu_model == sparc_leon)
> - return &dma_direct_ops;
> + return NULL;
> #endif
> #if defined(CONFIG_SPARC32) && defined(CONFIG_PCI)
> if (bus == &pci_bus_type)
> - return &dma_direct_ops;
> + return NULL;
> #endif
> return dma_ops;
> }
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index f4562fcec681..d460998ae828 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -17,7 +17,7 @@
>
> static bool disable_dac_quirk __read_mostly;
>
> -const struct dma_map_ops *dma_ops = &dma_direct_ops;
> +const struct dma_map_ops *dma_ops;
> EXPORT_SYMBOL(dma_ops);
>
> #ifdef CONFIG_IOMMU_DEBUG
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 61a84b958d67..50637f372e9f 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -581,7 +581,7 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
>
> dev_priv->map_mode = vmw_dma_map_populate;
>
> - if (dma_ops->sync_single_for_cpu)
> + if (dma_ops && dma_ops->sync_single_for_cpu)
> dev_priv->map_mode = vmw_dma_alloc_coherent;
> #ifdef CONFIG_SWIOTLB
> if (swiotlb_nr_tbl() == 0)
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index c5d6c7c42b0a..567221cca13c 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2184,7 +2184,7 @@ static int amd_iommu_add_device(struct device *dev)
> dev_name(dev));
>
> iommu_ignore_device(dev);
> - dev->dma_ops = &dma_direct_ops;
> + dev->dma_ops = NULL;
> goto out;
> }
> init_iommu_group(dev);
> @@ -2770,17 +2770,6 @@ int __init amd_iommu_init_dma_ops(void)
> swiotlb = (iommu_pass_through || sme_me_mask) ? 1 : 0;
> iommu_detected = 1;
>
> - /*
> - * In case we don't initialize SWIOTLB (actually the common case
> - * when AMD IOMMU is enabled and SME is not active), make sure there
> - * are global dma_ops set as a fall-back for devices not handled by
> - * this driver (for example non-PCI devices). When SME is active,
> - * make sure that swiotlb variable remains set so the global dma_ops
> - * continue to be SWIOTLB.
> - */
> - if (!swiotlb)
> - dma_ops = &dma_direct_ops;
> -
> if (amd_iommu_unmap_flush)
> pr_info("AMD-Vi: IO/TLB flush on unmap enabled\n");
> else
> diff --git a/include/asm-generic/dma-mapping.h b/include/asm-generic/dma-mapping.h
> index 880a292d792f..c13f46109e88 100644
> --- a/include/asm-generic/dma-mapping.h
> +++ b/include/asm-generic/dma-mapping.h
> @@ -4,7 +4,7 @@
>
> static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
> {
> - return &dma_direct_ops;
> + return NULL;
> }
>
> #endif /* _ASM_GENERIC_DMA_MAPPING_H */
> diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
> index 3b0a3ea3876d..b7338702592a 100644
> --- a/include/linux/dma-direct.h
> +++ b/include/linux/dma-direct.h
> @@ -60,22 +60,5 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
> struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
> dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs);
> void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page);
> -dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
> - unsigned long offset, size_t size, enum dma_data_direction dir,
> - unsigned long attrs);
> -void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> - size_t size, enum dma_data_direction dir, unsigned long attrs);
> -int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
> - enum dma_data_direction dir, unsigned long attrs);
> -void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
> - int nents, enum dma_data_direction dir, unsigned long attrs);
> -void dma_direct_sync_single_for_device(struct device *dev,
> - dma_addr_t addr, size_t size, enum dma_data_direction dir);
> -void dma_direct_sync_sg_for_device(struct device *dev,
> - struct scatterlist *sgl, int nents, enum dma_data_direction dir);
> -void dma_direct_sync_single_for_cpu(struct device *dev,
> - dma_addr_t addr, size_t size, enum dma_data_direction dir);
> -void dma_direct_sync_sg_for_cpu(struct device *dev,
> - struct scatterlist *sgl, int nents, enum dma_data_direction dir);
> int dma_direct_supported(struct device *dev, u64 mask);
> #endif /* _LINUX_DMA_DIRECT_H */
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 269ee27fc3d9..f422aec0f53c 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -134,7 +134,6 @@ struct dma_map_ops {
>
> #define DMA_MAPPING_ERROR (~(dma_addr_t)0)
>
> -extern const struct dma_map_ops dma_direct_ops;
> extern const struct dma_map_ops dma_virt_ops;
> extern const struct dma_map_ops dma_dummy_ops;
>
> @@ -222,6 +221,69 @@ static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
> }
> #endif
>
> +static inline bool dma_is_direct(const struct dma_map_ops *ops)
> +{
> + return likely(!ops);
> +}
> +
> +/*
> + * All the dma_direct_* declarations are here just for the indirect call bypass,
> + * and must not be used directly drivers!
> + */
> +dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
> + unsigned long offset, size_t size, enum dma_data_direction dir,
> + unsigned long attrs);
> +int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
> + enum dma_data_direction dir, unsigned long attrs);
> +
> +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> + defined(CONFIG_SWIOTLB)
> +void dma_direct_sync_single_for_device(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir);
> +void dma_direct_sync_sg_for_device(struct device *dev,
> + struct scatterlist *sgl, int nents, enum dma_data_direction dir);
> +#else
> +static inline void dma_direct_sync_single_for_device(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
> +{
> +}
> +static inline void dma_direct_sync_sg_for_device(struct device *dev,
> + struct scatterlist *sgl, int nents, enum dma_data_direction dir)
> +{
> +}
> +#endif
> +
> +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
> + defined(CONFIG_SWIOTLB)
> +void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> + size_t size, enum dma_data_direction dir, unsigned long attrs);
> +void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
> + int nents, enum dma_data_direction dir, unsigned long attrs);
> +void dma_direct_sync_single_for_cpu(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir);
> +void dma_direct_sync_sg_for_cpu(struct device *dev,
> + struct scatterlist *sgl, int nents, enum dma_data_direction dir);
> +#else
> +static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> + size_t size, enum dma_data_direction dir, unsigned long attrs)
> +{
> +}
> +static inline void dma_direct_unmap_sg(struct device *dev,
> + struct scatterlist *sgl, int nents, enum dma_data_direction dir,
> + unsigned long attrs)
> +{
> +}
> +static inline void dma_direct_sync_single_for_cpu(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
> +{
> +}
> +static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
> + struct scatterlist *sgl, int nents, enum dma_data_direction dir)
> +{
> +}
> +#endif
> +
> static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
> size_t size,
> enum dma_data_direction dir,
> @@ -232,9 +294,12 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
>
> BUG_ON(!valid_dma_direction(dir));
> debug_dma_map_single(dev, ptr, size);
> - addr = ops->map_page(dev, virt_to_page(ptr),
> - offset_in_page(ptr), size,
> - dir, attrs);
> + if (dma_is_direct(ops))
> + addr = dma_direct_map_page(dev, virt_to_page(ptr),
> + offset_in_page(ptr), size, dir, attrs);
> + else
> + addr = ops->map_page(dev, virt_to_page(ptr),
> + offset_in_page(ptr), size, dir, attrs);
> debug_dma_map_page(dev, virt_to_page(ptr),
> offset_in_page(ptr), size,
> dir, addr, true);
> @@ -249,7 +314,9 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->unmap_page)
> + if (dma_is_direct(ops))
> + dma_direct_unmap_page(dev, addr, size, dir, attrs);
> + else if (ops->unmap_page)
> ops->unmap_page(dev, addr, size, dir, attrs);
> debug_dma_unmap_page(dev, addr, size, dir, true);
> }
> @@ -272,7 +339,10 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
> int ents;
>
> BUG_ON(!valid_dma_direction(dir));
> - ents = ops->map_sg(dev, sg, nents, dir, attrs);
> + if (dma_is_direct(ops))
> + ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
> + else
> + ents = ops->map_sg(dev, sg, nents, dir, attrs);
> BUG_ON(ents < 0);
> debug_dma_map_sg(dev, sg, nents, ents, dir);
>
> @@ -287,7 +357,9 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
>
> BUG_ON(!valid_dma_direction(dir));
> debug_dma_unmap_sg(dev, sg, nents, dir);
> - if (ops->unmap_sg)
> + if (dma_is_direct(ops))
> + dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
> + else if (ops->unmap_sg)
> ops->unmap_sg(dev, sg, nents, dir, attrs);
> }
>
> @@ -301,7 +373,10 @@ static inline dma_addr_t dma_map_page_attrs(struct device *dev,
> dma_addr_t addr;
>
> BUG_ON(!valid_dma_direction(dir));
> - addr = ops->map_page(dev, page, offset, size, dir, attrs);
> + if (dma_is_direct(ops))
> + addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
> + else
> + addr = ops->map_page(dev, page, offset, size, dir, attrs);
> debug_dma_map_page(dev, page, offset, size, dir, addr, false);
>
> return addr;
> @@ -322,7 +397,7 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
> BUG_ON(pfn_valid(PHYS_PFN(phys_addr)));
>
> addr = phys_addr;
> - if (ops->map_resource)
> + if (ops && ops->map_resource)
> addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
>
> debug_dma_map_resource(dev, phys_addr, size, dir, addr);
> @@ -337,7 +412,7 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->unmap_resource)
> + if (ops && ops->unmap_resource)
> ops->unmap_resource(dev, addr, size, dir, attrs);
> debug_dma_unmap_resource(dev, addr, size, dir);
> }
> @@ -349,7 +424,9 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->sync_single_for_cpu)
> + if (dma_is_direct(ops))
> + dma_direct_sync_single_for_cpu(dev, addr, size, dir);
> + else if (ops->sync_single_for_cpu)
> ops->sync_single_for_cpu(dev, addr, size, dir);
> debug_dma_sync_single_for_cpu(dev, addr, size, dir);
> }
> @@ -368,7 +445,9 @@ static inline void dma_sync_single_for_device(struct device *dev,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->sync_single_for_device)
> + if (dma_is_direct(ops))
> + dma_direct_sync_single_for_device(dev, addr, size, dir);
> + else if (ops->sync_single_for_device)
> ops->sync_single_for_device(dev, addr, size, dir);
> debug_dma_sync_single_for_device(dev, addr, size, dir);
> }
> @@ -387,7 +466,9 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->sync_sg_for_cpu)
> + if (dma_is_direct(ops))
> + dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
> + else if (ops->sync_sg_for_cpu)
> ops->sync_sg_for_cpu(dev, sg, nelems, dir);
> debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
> }
> @@ -399,7 +480,9 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->sync_sg_for_device)
> + if (dma_is_direct(ops))
> + dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
> + else if (ops->sync_sg_for_device)
> ops->sync_sg_for_device(dev, sg, nelems, dir);
> debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
>
> diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h
> index 306557331d7d..69b36ed31a99 100644
> --- a/include/linux/dma-noncoherent.h
> +++ b/include/linux/dma-noncoherent.h
> @@ -38,7 +38,10 @@ pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> void arch_dma_cache_sync(struct device *dev, void *vaddr, size_t size,
> enum dma_data_direction direction);
> #else
> -#define arch_dma_cache_sync NULL
> +static inline void arch_dma_cache_sync(struct device *dev, void *vaddr,
> + size_t size, enum dma_data_direction direction)
> +{
> +}
> #endif /* CONFIG_DMA_NONCOHERENT_CACHE_SYNC */
>
> #ifdef CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 85d8286a0ba2..79da61b49fa4 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -223,6 +223,7 @@ void dma_direct_sync_single_for_device(struct device *dev,
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_device(dev, paddr, size, dir);
> }
> +EXPORT_SYMBOL(dma_direct_sync_single_for_device);
>
> void dma_direct_sync_sg_for_device(struct device *dev,
> struct scatterlist *sgl, int nents, enum dma_data_direction dir)
> @@ -240,6 +241,7 @@ void dma_direct_sync_sg_for_device(struct device *dev,
> dir);
> }
> }
> +EXPORT_SYMBOL(dma_direct_sync_sg_for_device);
> #endif
>
> #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> @@ -258,6 +260,7 @@ void dma_direct_sync_single_for_cpu(struct device *dev,
> if (unlikely(is_swiotlb_buffer(paddr)))
> swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
> }
> +EXPORT_SYMBOL(dma_direct_sync_single_for_cpu);
>
> void dma_direct_sync_sg_for_cpu(struct device *dev,
> struct scatterlist *sgl, int nents, enum dma_data_direction dir)
> @@ -277,6 +280,7 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_cpu_all(dev);
> }
> +EXPORT_SYMBOL(dma_direct_sync_sg_for_cpu);
>
> void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> size_t size, enum dma_data_direction dir, unsigned long attrs)
> @@ -289,6 +293,7 @@ void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> if (unlikely(is_swiotlb_buffer(phys)))
> swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> }
> +EXPORT_SYMBOL(dma_direct_unmap_page);
>
> void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
> int nents, enum dma_data_direction dir, unsigned long attrs)
> @@ -300,11 +305,7 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
> dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir,
> attrs);
> }
> -#else
> -void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
> - int nents, enum dma_data_direction dir, unsigned long attrs)
> -{
> -}
> +EXPORT_SYMBOL(dma_direct_unmap_sg);
> #endif
>
> static inline bool dma_direct_possible(struct device *dev, dma_addr_t dma_addr,
> @@ -331,6 +332,7 @@ dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
> arch_sync_dma_for_device(dev, phys, size, dir);
> return dma_addr;
> }
> +EXPORT_SYMBOL(dma_direct_map_page);
>
> int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
> enum dma_data_direction dir, unsigned long attrs)
> @@ -352,6 +354,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
> dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
> return 0;
> }
> +EXPORT_SYMBOL(dma_direct_map_sg);
>
> /*
> * Because 32-bit DMA masks are so common we expect every architecture to be
> @@ -372,27 +375,3 @@ int dma_direct_supported(struct device *dev, u64 mask)
>
> return mask >= phys_to_dma(dev, min_mask);
> }
> -
> -const struct dma_map_ops dma_direct_ops = {
> - .alloc = dma_direct_alloc,
> - .free = dma_direct_free,
> - .map_page = dma_direct_map_page,
> - .map_sg = dma_direct_map_sg,
> -#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> - defined(CONFIG_SWIOTLB)
> - .sync_single_for_device = dma_direct_sync_single_for_device,
> - .sync_sg_for_device = dma_direct_sync_sg_for_device,
> -#endif
> -#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> - defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
> - defined(CONFIG_SWIOTLB)
> - .sync_single_for_cpu = dma_direct_sync_single_for_cpu,
> - .sync_sg_for_cpu = dma_direct_sync_sg_for_cpu,
> - .unmap_page = dma_direct_unmap_page,
> - .unmap_sg = dma_direct_unmap_sg,
> -#endif
> - .get_required_mask = dma_direct_get_required_mask,
> - .dma_supported = dma_direct_supported,
> - .cache_sync = arch_dma_cache_sync,
> -};
> -EXPORT_SYMBOL(dma_direct_ops);
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 0b18cfbdde95..fc84c81029d9 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -7,6 +7,7 @@
> */
> #include <linux/memblock.h> /* for max_pfn */
> #include <linux/acpi.h>
> +#include <linux/dma-direct.h>
> #include <linux/dma-noncoherent.h>
> #include <linux/export.h>
> #include <linux/gfp.h>
> @@ -229,8 +230,8 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
> unsigned long attrs)
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
> - BUG_ON(!ops);
> - if (ops->get_sgtable)
> +
> + if (!dma_is_direct(ops) && ops->get_sgtable)
> return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
> attrs);
> return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
> @@ -293,8 +294,8 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
> unsigned long attrs)
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
> - BUG_ON(!ops);
> - if (ops->mmap)
> +
> + if (!dma_is_direct(ops) && ops->mmap)
> return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
> return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
> }
> @@ -324,6 +325,8 @@ u64 dma_get_required_mask(struct device *dev)
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> + if (dma_is_direct(ops))
> + return dma_direct_get_required_mask(dev);
> if (ops->get_required_mask)
> return ops->get_required_mask(dev);
> return dma_default_get_required_mask(dev);
> @@ -341,7 +344,6 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
> const struct dma_map_ops *ops = get_dma_ops(dev);
> void *cpu_addr;
>
> - BUG_ON(!ops);
> WARN_ON_ONCE(dev && !dev->coherent_dma_mask);
>
> if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))
> @@ -352,10 +354,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
>
> if (!arch_dma_alloc_attrs(&dev))
> return NULL;
> - if (!ops->alloc)
> +
> + if (dma_is_direct(ops))
> + cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
> + else if (ops->alloc)
> + cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
> + else
> return NULL;
>
> - cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
> debug_dma_alloc_coherent(dev, size, *dma_handle, cpu_addr);
> return cpu_addr;
> }
> @@ -366,8 +372,6 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> - BUG_ON(!ops);
> -
> if (dma_release_from_dev_coherent(dev, get_order(size), cpu_addr))
> return;
> /*
> @@ -379,11 +383,14 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
> */
> WARN_ON(irqs_disabled());
>
> - if (!ops->free || !cpu_addr)
> + if (!cpu_addr)
> return;
>
> debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
> - ops->free(dev, size, cpu_addr, dma_handle, attrs);
> + if (dma_is_direct(ops))
> + dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
> + else if (ops->free)
> + ops->free(dev, size, cpu_addr, dma_handle, attrs);
> }
> EXPORT_SYMBOL(dma_free_attrs);
>
> @@ -397,9 +404,9 @@ int dma_supported(struct device *dev, u64 mask)
> {
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> - if (!ops)
> - return 0;
> - if (!ops->dma_supported)
> + if (dma_is_direct(ops))
> + return dma_direct_supported(dev, mask);
> + if (ops->dma_supported)
> return 1;
> return ops->dma_supported(dev, mask);
> }
> @@ -437,7 +444,10 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
> const struct dma_map_ops *ops = get_dma_ops(dev);
>
> BUG_ON(!valid_dma_direction(dir));
> - if (ops->cache_sync)
> +
> + if (dma_is_direct(ops))
> + arch_dma_cache_sync(dev, vaddr, size, dir);
> + else if (ops->cache_sync)
> ops->cache_sync(dev, vaddr, size, dir);
> }
> EXPORT_SYMBOL(dma_cache_sync);

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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