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SubjectRe: [PATCH 7/7] arc: use the generic remapping allocator for coherent DMA allocations
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Hi Christoph,

Regular question - do you have any public git repository with all this dma changes?
I want to test it for ARC.

Pretty sure the
[PATCH 2/7] arc: remove the partial DMA_ATTR_NON_CONSISTENT support
is fine.

Not so sure about
[PATCH 7/7] arc: use the generic remapping allocator for coherent DMA allocations
:)

On Fri, 2019-06-14 at 16:44 +0200, Christoph Hellwig wrote:
> Replace the code that sets up uncached PTEs with the generic vmap based
> remapping code. It also provides an atomic pool for allocations from
> non-blocking context, which we not properly supported by the existing
> arc code.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/arc/Kconfig | 2 ++
> arch/arc/mm/dma.c | 62 ++++++++---------------------------------------
> 2 files changed, 12 insertions(+), 52 deletions(-)
>
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 23e063df5d2c..cdad7d30ff1d 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -10,6 +10,7 @@ config ARC
> def_bool y
> select ARC_TIMERS
> select ARCH_HAS_DMA_COHERENT_TO_PFN
> + select ARCH_HAS_DMA_PREP_COHERENT
> select ARCH_HAS_PTE_SPECIAL
> select ARCH_HAS_SETUP_DMA_OPS
> select ARCH_HAS_SYNC_DMA_FOR_CPU
> @@ -19,6 +20,7 @@ config ARC
> select BUILDTIME_EXTABLE_SORT
> select CLONE_BACKWARDS
> select COMMON_CLK
> + select DMA_DIRECT_REMAP
> select GENERIC_ATOMIC64 if !ISA_ARCV2 || !(ARC_HAS_LL64 && ARC_HAS_LLSC)
> select GENERIC_CLOCKEVENTS
> select GENERIC_FIND_FIRST_BIT
> diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
> index 9832928f896d..0fa850709fac 100644
> --- a/arch/arc/mm/dma.c
> +++ b/arch/arc/mm/dma.c
> @@ -11,46 +11,15 @@
> #include <asm/cacheflush.h>
>
> /*
> - * ARCH specific callbacks for generic noncoherent DMA ops (dma/noncoherent.c)
> + * ARCH specific callbacks for generic noncoherent DMA ops
> * - hardware IOC not available (or "dma-coherent" not set for device in DT)
> * - But still handle both coherent and non-coherent requests from caller
> *
> * For DMA coherent hardware (IOC) generic code suffices
> */
> -void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> - gfp_t gfp, unsigned long attrs)
> -{
> - unsigned long order = get_order(size);
> - struct page *page;
> - phys_addr_t paddr;
> - void *kvaddr;
> -
> - /*
> - * __GFP_HIGHMEM flag is cleared by upper layer functions
> - * (in include/linux/dma-mapping.h) so we should never get a
> - * __GFP_HIGHMEM here.
> - */
> - BUG_ON(gfp & __GFP_HIGHMEM);
> -
> - page = alloc_pages(gfp | __GFP_ZERO, order);
> - if (!page)
> - return NULL;
> -
> - /* This is linear addr (0x8000_0000 based) */
> - paddr = page_to_phys(page);
> -
> - *dma_handle = paddr;
> -
> - /*
> - * A coherent buffer needs MMU mapping to enforce non-cachability.
> - * kvaddr is kernel Virtual address (0x7000_0000 based).
> - */
> - kvaddr = ioremap_nocache(paddr, size);
> - if (kvaddr == NULL) {
> - __free_pages(page, order);
> - return NULL;
> - }
>
> +void arch_dma_prep_coherent(struct page *page, size_t size)
> +{
> /*
> * Evict any existing L1 and/or L2 lines for the backing page
> * in case it was used earlier as a normal "cached" page.
> @@ -61,24 +30,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> * Currently flush_cache_vmap nukes the L1 cache completely which
> * will be optimized as a separate commit
> */
> - dma_cache_wback_inv(paddr, size);
> - return kvaddr;
> -}
> -
> -void arch_dma_free(struct device *dev, size_t size, void *vaddr,
> - dma_addr_t dma_handle, unsigned long attrs)
> -{
> - phys_addr_t paddr = dma_handle;
> - struct page *page = virt_to_page(paddr);
> -
> - iounmap((void __force __iomem *)vaddr);
> - __free_pages(page, get_order(size));
> -}
> -
> -long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
> - dma_addr_t dma_addr)
> -{
> - return __phys_to_pfn(dma_addr);
> + dma_cache_wback_inv(page_to_phys(page), size);
> }
>
> /*
> @@ -155,3 +107,9 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> dev_info(dev, "use %sncoherent DMA ops\n",
> dev->dma_coherent ? "" : "non");
> }
> +
> +static int __init atomic_pool_init(void)
> +{
> + return dma_atomic_pool_init(GFP_KERNEL, pgprot_noncached(PAGE_KERNEL));
> +}
> +postcore_initcall(atomic_pool_init);
--
Eugeniy Paltsev
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