linux-kernel - Re: [PATCH 1/2] nios2: use the generic uncached segment support in dma-direct

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Date:   Tue, 25 Jun 2019 13:29:40 +0800
From:   Ley Foon Tan <lftan@...era.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Michal Simek <monstr@...str.eu>, linux-mips@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] nios2: use the generic uncached segment support in dma-direct

On Mon, Jun 3, 2019 at 2:54 PM Christoph Hellwig <hch@....de> wrote:
>
> Stop providing our own arch alloc/free hooks and just expose the segment
> offset and use the generic dma-direct allocator.
>
> Signed-off-by: Christoph Hellwig <hch@....de>

Acked-by: Ley Foon Tan <ley.foon.tan@...el.com>

> ---
>  arch/nios2/Kconfig            |  1 +
>  arch/nios2/include/asm/page.h |  6 ------
>  arch/nios2/mm/dma-mapping.c   | 34 +++++++++++++++-------------------
>  3 files changed, 16 insertions(+), 25 deletions(-)
>
> diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
> index 26a9c760a98b..44b5da37e8bd 100644
> --- a/arch/nios2/Kconfig
> +++ b/arch/nios2/Kconfig
> @@ -4,6 +4,7 @@ config NIOS2
>         select ARCH_32BIT_OFF_T
>         select ARCH_HAS_SYNC_DMA_FOR_CPU
>         select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> +       select ARCH_HAS_UNCACHED_SEGMENT
>         select ARCH_NO_SWAP
>         select TIMER_OF
>         select GENERIC_ATOMIC64
> diff --git a/arch/nios2/include/asm/page.h b/arch/nios2/include/asm/page.h
> index f1fbdc47bdaf..79fcac61f6ef 100644
> --- a/arch/nios2/include/asm/page.h
> +++ b/arch/nios2/include/asm/page.h
> @@ -101,12 +101,6 @@ static inline bool pfn_valid(unsigned long pfn)
>  # define VM_DATA_DEFAULT_FLAGS (VM_READ | VM_WRITE | \
>                                  VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
>
> -# define UNCAC_ADDR(addr)      \
> -       ((void *)((unsigned)(addr) | CONFIG_NIOS2_IO_REGION_BASE))
> -# define CAC_ADDR(addr)                \
> -       ((void *)(((unsigned)(addr) & ~CONFIG_NIOS2_IO_REGION_BASE) |   \
> -               CONFIG_NIOS2_KERNEL_REGION_BASE))
> -
>  #include <asm-generic/memory_model.h>
>
>  #include <asm-generic/getorder.h>
> diff --git a/arch/nios2/mm/dma-mapping.c b/arch/nios2/mm/dma-mapping.c
> index 4af9e5b5ba1c..9cb238664584 100644
> --- a/arch/nios2/mm/dma-mapping.c
> +++ b/arch/nios2/mm/dma-mapping.c
> @@ -60,32 +60,28 @@ void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
>         }
>  }
>
> -void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
> -               gfp_t gfp, unsigned long attrs)
> +void arch_dma_prep_coherent(struct page *page, size_t size)
>  {
> -       void *ret;
> +       unsigned long start = (unsigned long)page_address(page);
>
> -       /* optimized page clearing */
> -       gfp |= __GFP_ZERO;
> +       flush_dcache_range(start, start + size);
> +}
>
> -       if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
> -               gfp |= GFP_DMA;
> +void *uncached_kernel_address(void *ptr)
> +{
> +       unsigned long addr = (unsigned long)ptr;
>
> -       ret = (void *) __get_free_pages(gfp, get_order(size));
> -       if (ret != NULL) {
> -               *dma_handle = virt_to_phys(ret);
> -               flush_dcache_range((unsigned long) ret,
> -                       (unsigned long) ret + size);
> -               ret = UNCAC_ADDR(ret);
> -       }
> +       addr |= CONFIG_NIOS2_IO_REGION_BASE;
>
> -       return ret;
> +       return (void *)ptr;
>  }
>
> -void arch_dma_free(struct device *dev, size_t size, void *vaddr,
> -               dma_addr_t dma_handle, unsigned long attrs)
> +void *cached_kernel_address(void *ptr)
>  {
> -       unsigned long addr = (unsigned long) CAC_ADDR((unsigned long) vaddr);
> +       unsigned long addr = (unsigned long)ptr;
> +
> +       addr &= ~CONFIG_NIOS2_IO_REGION_BASE;
> +       addr |= CONFIG_NIOS2_KERNEL_REGION_BASE;
>
> -       free_pages(addr, get_order(size));
> +       return (void *)ptr;
>  }
> --
> 2.20.1
>