[RFC PATCH v3] arm DMA: Fix allocation from CMA for coherent DMA
From: catalin.marinas@arm.com (Catalin Marinas)
Date: 2015-06-26 16:26:03
Also in:
lkml
On Thu, Jun 18, 2015 at 11:44:22PM +0200, Lorenzo Nava wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 7e7583d..8e7f402 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c@@ -645,15 +645,29 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, size = PAGE_ALIGN(size); want_vaddr = !dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs); - if (is_coherent || nommu()) + if (nommu()) { addr = __alloc_simple_buffer(dev, size, gfp, &page); - else if (!(gfp & __GFP_WAIT)) + goto dma_alloc_done; + } + + if (dev_get_cma_area(dev) && (gfp & __GFP_WAIT)) { + addr = __alloc_from_contiguous(dev, size, prot, &page, + caller, want_vaddr); + goto dma_alloc_done; + } + + if (is_coherent) { + addr = __alloc_simple_buffer(dev, size, gfp, &page); + goto dma_alloc_done; + } + + if (!(gfp & __GFP_WAIT)) addr = __alloc_from_pool(size, &page); - else if (!dev_get_cma_area(dev)) - addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller, want_vaddr); else - addr = __alloc_from_contiguous(dev, size, prot, &page, caller, want_vaddr); + addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, + caller, want_vaddr); +dma_alloc_done: if (page) *handle = pfn_to_dma(dev, page_to_pfn(page));
The logic here looks alright but I would have preferred the original more concise "if ... else if" constructs than the gotos (just personal preference).
quoted hunk ↗ jump to hunk
@@ -680,9 +694,14 @@ void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, static void *arm_coherent_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs) { - pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL); + pgprot_t prot; void *memory; + if (attrs == NULL) + prot = PAGE_KERNEL; + else + prot = __get_dma_pgprot(attrs, PAGE_KERNEL); + if (dma_alloc_from_coherent(dev, size, handle, &memory)) return memory;
I still think this is the wrong way to fix. It doesn't address the coherent dma mmap operation. I already replied on the previous version that we should rather have an extra argument "coherent" to __get_dma_pgprot().
quoted hunk ↗ jump to hunk
@@ -735,12 +754,12 @@ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr, size = PAGE_ALIGN(size); - if (is_coherent || nommu()) { + if (nommu()) { __dma_free_buffer(page, size); } else if (__free_from_pool(cpu_addr, size)) { return;
You have an unnecessary __free_from_pool() call here in the is_coherent case.
} else if (!dev_get_cma_area(dev)) {
- if (want_vaddr)
+ if (want_vaddr && !is_coherent)
__dma_free_remap(cpu_addr, size);
__dma_free_buffer(page, size);
} else {-- Catalin