On Sat, 2018-12-08 at 09:36 -0800, Christoph Hellwig wrote:
> For the iommu ops we can just use the implementaton for DMA coherent
> devices. For the regular ops we need mix and match a bit so that
> we either use the CMA allocator without remapping, but with a special
> error handling case for highmem pages, or the simple allocator.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> arch/arm/mm/dma-mapping.c | 49 ++++++++++++++++++++++++++++-----------
> 1 file changed, 35 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 2cfb17bad1e6..b3b66b41c450 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -49,6 +49,7 @@ struct arm_dma_alloc_args {
> const void *caller;
> bool want_vaddr;
> int coherent_flag;
> + bool nonconsistent_flag;
> };
>
> struct arm_dma_free_args {
> @@ -57,6 +58,7 @@ struct arm_dma_free_args {
> void *cpu_addr;
> struct page *page;
> bool want_vaddr;
> + bool nonconsistent_flag;
> };
>
> #define NORMAL 0
> @@ -348,7 +350,8 @@ static void __dma_free_buffer(struct page *page, size_t size)
> static void *__alloc_from_contiguous(struct device *dev, size_t size,
> pgprot_t prot, struct page **ret_page,
> const void *caller, bool want_vaddr,
> - int coherent_flag, gfp_t gfp);
> + int coherent_flag, bool nonconsistent_flag,
> + gfp_t gfp);
>
> static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
> pgprot_t prot, struct page **ret_page,
> @@ -405,7 +408,7 @@ static int __init atomic_pool_init(void)
> if (dev_get_cma_area(NULL))
> ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
> &page, atomic_pool_init, true, NORMAL,
> - GFP_KERNEL);
> + false, GFP_KERNEL);
> else
> ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
> &page, atomic_pool_init, true);
> @@ -579,7 +582,8 @@ static int __free_from_pool(void *start, size_t size)
> static void *__alloc_from_contiguous(struct device *dev, size_t size,
> pgprot_t prot, struct page **ret_page,
> const void *caller, bool want_vaddr,
> - int coherent_flag, gfp_t gfp)
> + int coherent_flag, bool nonconsistent_flag,
> + gfp_t gfp)
> {
> unsigned long order = get_order(size);
> size_t count = size >> PAGE_SHIFT;
> @@ -595,12 +599,16 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
> if (!want_vaddr)
> goto out;
>
> + if (nonconsistent_flag) {
> + if (PageHighMem(page))
> + goto fail;
> + goto out;
> + }
> +
> if (PageHighMem(page)) {
> ptr = __dma_alloc_remap(page, size, GFP_KERNEL, prot, caller);
> - if (!ptr) {
> - dma_release_from_contiguous(dev, page, count);
> - return NULL;
> - }
> + if (!ptr)
> + goto fail;
> } else {
> __dma_remap(page, size, prot);
> ptr = page_address(page);
> @@ -609,12 +617,15 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
> out:
> *ret_page = page;
> return ptr;
> + fail:
> + dma_release_from_contiguous(dev, page, count);
> + return NULL;
> }
>
> static void __free_from_contiguous(struct device *dev, struct page *page,
> - void *cpu_addr, size_t size, bool want_vaddr)
> + void *cpu_addr, size_t size, bool remapped)
> {
> - if (want_vaddr) {
> + if (remapped) {
> if (PageHighMem(page))
> __dma_free_remap(cpu_addr, size);
> else
> @@ -635,7 +646,11 @@ static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
> struct page **ret_page)
> {
> struct page *page;
> - /* __alloc_simple_buffer is only called when the device is coherent */
> + /*
> + * __alloc_simple_buffer is only called when the device is coherent,
> + * or if the caller explicitly asked for an allocation that is not
> + * consistent.
> + */
> page = __dma_alloc_buffer(dev, size, gfp, COHERENT);
> if (!page)
> return NULL;
> @@ -667,13 +682,15 @@ static void *cma_allocator_alloc(struct arm_dma_alloc_args *args,
> return __alloc_from_contiguous(args->dev, args->size, args->prot,
> ret_page, args->caller,
> args->want_vaddr, args->coherent_flag,
> + args->nonconsistent_flag,
> args->gfp);
> }
>
> static void cma_allocator_free(struct arm_dma_free_args *args)
> {
> __free_from_contiguous(args->dev, args->page, args->cpu_addr,
> - args->size, args->want_vaddr);
> + args->size,
> + args->want_vaddr || args->nonconsistent_flag);
> }
>
> static struct arm_dma_allocator cma_allocator = {
> @@ -735,6 +752,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> .caller = caller,
> .want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
> .coherent_flag = is_coherent ? COHERENT : NORMAL,
> + .nonconsistent_flag = (attrs & DMA_ATTR_NON_CONSISTENT),
> };
>
> #ifdef CONFIG_DMA_API_DEBUG
> @@ -773,7 +791,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
>
> if (cma)
> buf->allocator = &cma_allocator;
> - else if (is_coherent)
> + else if (is_coherent || (attrs & DMA_ATTR_NON_CONSISTENT))
> buf->allocator = &simple_allocator;
Reading through your code I can't really see where the pgprot is changed
for non-consistent requests. Namely, __get_dma_pgprot only
returns writecombine or coherent memory.
Regards,
Ezequiel
