Re: [PATCHv2] arm64: Add atomic pool for non-coherent and CMA allocaitons.

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This patch addresses the issues I had previously run into.

Dave

On Mon, Jun 2, 2014 at 1:03 PM, Laura Abbott <lauraa@xxxxxxxxxxxxxx> wrote:
> Neither CMA nor noncoherent allocations support atomic allocations.
> Add a dedicated atomic pool to support this.
>
> Change-Id: I46c8fdffe5e0687403d42b37643137c8cf344259
> Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
> ---
>
> v2: Various bug fixes pointed out by David and Ritesh (CMA dependency, swapping
> coherent, noncoherent). I'm still not sure how to address the devicetree
> suggestion by Will [1][2]. I added the devicetree mailing list this time around
> to get more input on this.
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-April/249180.html
> [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-April/249528.html
>
> ---
>  arch/arm64/mm/dma-mapping.c | 192 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 190 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index c851eb4..792d43c 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -41,6 +41,110 @@ static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot,
>         return prot;
>  }
>
> +#define DEFAULT_DMA_COHERENT_POOL_SIZE  SZ_256K
> +
> +struct dma_pool {
> +       size_t size;
> +       spinlock_t lock;
> +       void *coherent_vaddr;
> +       void *noncoherent_vaddr;
> +       unsigned long *bitmap;
> +       unsigned long nr_pages;
> +       struct page **pages;
> +};
> +
> +static struct dma_pool atomic_pool = {
> +       .size = DEFAULT_DMA_COHERENT_POOL_SIZE,
> +};
> +
> +static int __init early_coherent_pool(char *p)
> +{
> +       atomic_pool.size = memparse(p, &p);
> +       return 0;
> +}
> +early_param("coherent_pool", early_coherent_pool);
> +
> +static void *__alloc_from_pool(size_t size, struct page **ret_page,
> +                                       bool coherent)
> +{
> +       struct dma_pool *pool = &atomic_pool;
> +       unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> +       unsigned int pageno;
> +       unsigned long flags;
> +       void *ptr = NULL;
> +       unsigned long align_mask;
> +       void *pool_start = coherent ? pool->coherent_vaddr :
> +                                     pool->noncoherent_vaddr;
> +
> +       if (!pool->coherent_vaddr || !pool->noncoherent_vaddr) {
> +               WARN(1, "Atomic pool not initialised!\n");
> +               return NULL;
> +       }
> +
> +       /*
> +        * Align the region allocation - allocations from pool are rather
> +        * small, so align them to their order in pages, minimum is a page
> +        * size. This helps reduce fragmentation of the DMA space.
> +        */
> +       align_mask = (1 << get_order(size)) - 1;
> +
> +       spin_lock_irqsave(&pool->lock, flags);
> +       pageno = bitmap_find_next_zero_area(pool->bitmap, pool->nr_pages,
> +                                           0, count, align_mask);
> +       if (pageno < pool->nr_pages) {
> +               bitmap_set(pool->bitmap, pageno, count);
> +               ptr = pool_start + PAGE_SIZE * pageno;
> +               *ret_page = pool->pages[pageno];
> +       } else {
> +               pr_err_once("ERROR: %u KiB atomic DMA coherent pool is too small!\n"
> +                           "Please increase it with coherent_pool= kernel parameter!\n",
> +                               (unsigned)pool->size / 1024);
> +       }
> +       spin_unlock_irqrestore(&pool->lock, flags);
> +
> +       return ptr;
> +}
> +
> +static bool __in_atomic_pool(void *start, size_t size, void *pool_start)
> +{
> +       struct dma_pool *pool = &atomic_pool;
> +       void *end = start + size;
> +       void *pool_end = pool_start + pool->size;
> +
> +       if (start < pool_start || start >= pool_end)
> +               return false;
> +
> +       if (end <= pool_end)
> +               return true;
> +
> +       WARN(1, "Wrong coherent size(%p-%p) from atomic pool(%p-%p)\n",
> +               start, end - 1, pool_start, pool_end - 1);
> +
> +       return false;
> +}
> +
> +static int __free_from_pool(void *start, size_t size, bool coherent)
> +{
> +       struct dma_pool *pool = &atomic_pool;
> +       unsigned long pageno, count;
> +       unsigned long flags;
> +       void *pool_start = coherent ? pool->coherent_vaddr :
> +                                     pool->noncoherent_vaddr;
> +
> +       if (!__in_atomic_pool(start, size, pool_start))
> +               return 0;
> +
> +       pageno = (start - pool_start) >> PAGE_SHIFT;
> +       count = size >> PAGE_SHIFT;
> +
> +       spin_lock_irqsave(&pool->lock, flags);
> +       bitmap_clear(pool->bitmap, pageno, count);
> +       spin_unlock_irqrestore(&pool->lock, flags);
> +
> +       return 1;
> +}
> +
> +
>  static void *__dma_alloc_coherent(struct device *dev, size_t size,
>                                   dma_addr_t *dma_handle, gfp_t flags,
>                                   struct dma_attrs *attrs)
> @@ -53,7 +157,16 @@ static void *__dma_alloc_coherent(struct device *dev, size_t size,
>         if (IS_ENABLED(CONFIG_ZONE_DMA) &&
>             dev->coherent_dma_mask <= DMA_BIT_MASK(32))
>                 flags |= GFP_DMA;
> -       if (IS_ENABLED(CONFIG_DMA_CMA)) {
> +
> +       if (!(flags & __GFP_WAIT)) {
> +               struct page *page = NULL;
> +               void *addr = __alloc_from_pool(size, &page, true);
> +
> +               if (addr)
> +                       *dma_handle = phys_to_dma(dev, page_to_phys(page));
> +
> +               return addr;
> +       } else if (IS_ENABLED(CONFIG_DMA_CMA)) {
>                 struct page *page;
>
>                 size = PAGE_ALIGN(size);
> @@ -78,7 +191,9 @@ static void __dma_free_coherent(struct device *dev, size_t size,
>                 return;
>         }
>
> -       if (IS_ENABLED(CONFIG_DMA_CMA)) {
> +       if (__free_from_pool(vaddr, size, true)) {
> +               return;
> +       } else if (IS_ENABLED(CONFIG_DMA_CMA)) {
>                 phys_addr_t paddr = dma_to_phys(dev, dma_handle);
>
>                 dma_release_from_contiguous(dev,
> @@ -100,9 +215,21 @@ static void *__dma_alloc_noncoherent(struct device *dev, size_t size,
>         size = PAGE_ALIGN(size);
>         order = get_order(size);
>
> +       if (!(flags & __GFP_WAIT)) {
> +               struct page *page = NULL;
> +               void *addr = __alloc_from_pool(size, &page, false);
> +
> +               if (addr)
> +                       *dma_handle = phys_to_dma(dev, page_to_phys(page));
> +
> +               return addr;
> +
> +       }
> +
>         ptr = __dma_alloc_coherent(dev, size, dma_handle, flags, attrs);
>         if (!ptr)
>                 goto no_mem;
> +
>         map = kmalloc(sizeof(struct page *) << order, flags & ~GFP_DMA);
>         if (!map)
>                 goto no_map;
> @@ -135,6 +262,8 @@ static void __dma_free_noncoherent(struct device *dev, size_t size,
>  {
>         void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
>
> +       if (__free_from_pool(vaddr, size, false))
> +               return;
>         vunmap(vaddr);
>         __dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
>  }
> @@ -332,6 +461,65 @@ static struct notifier_block amba_bus_nb = {
>
>  extern int swiotlb_late_init_with_default_size(size_t default_size);
>
> +static int __init atomic_pool_init(void)
> +{
> +       struct dma_pool *pool = &atomic_pool;
> +       pgprot_t prot = pgprot_writecombine(pgprot_default);
> +       unsigned long nr_pages = pool->size >> PAGE_SHIFT;
> +       unsigned long *bitmap;
> +       struct page *page;
> +       struct page **pages;
> +       int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
> +
> +       bitmap = kzalloc(bitmap_size, GFP_KERNEL);
> +       if (!bitmap)
> +               goto no_bitmap;
> +
> +       pages = kzalloc(nr_pages * sizeof(struct page *), GFP_KERNEL);
> +       if (!pages)
> +               goto no_pages;
> +
> +       if (IS_ENABLED(CONFIG_CMA))
> +               page = dma_alloc_from_contiguous(NULL, nr_pages,
> +                                       get_order(pool->size));
> +       else
> +               page = alloc_pages(GFP_KERNEL, get_order(pool->size));
> +
> +
> +       if (page) {
> +               int i;
> +               void *addr = page_address(page);
> +
> +               memset(addr, 0, pool->size);
> +               __dma_flush_range(addr, addr + pool->size);
> +
> +               for (i = 0; i < nr_pages; i++)
> +                       pages[i] = page + i;
> +
> +               spin_lock_init(&pool->lock);
> +               pool->pages = pages;
> +               pool->noncoherent_vaddr = vmap(pages, nr_pages, VM_MAP, prot);
> +               if (pool->noncoherent_vaddr == NULL)
> +                       goto out;
> +               pool->coherent_vaddr = addr;
> +               pool->bitmap = bitmap;
> +               pool->nr_pages = nr_pages;
> +               pr_info("DMA: preallocated %u KiB pool for atomic allocations\n",
> +                       (unsigned)pool->size / 1024);
> +               return 0;
> +       }
> +
> +out:
> +       kfree(pages);
> +no_pages:
> +       kfree(bitmap);
> +no_bitmap:
> +       pr_err("DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
> +               (unsigned)pool->size / 1024);
> +       return -ENOMEM;
> +}
> +postcore_initcall(atomic_pool_init);
> +
>  static int __init swiotlb_late_init(void)
>  {
>         size_t swiotlb_size = min(SZ_64M, MAX_ORDER_NR_PAGES << PAGE_SHIFT);
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
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