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Date: Fri, 08 Aug 2014 16:25:58 -0700 From: Laura Abbott <lauraa@...eaurora.org> To: Andrew Morton <akpm@...ux-foundation.org> CC: David Riley <davidriley@...omium.org>, Arnd Bergmann <arnd@...db.de>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Thierry Reding <thierry.reding@...il.com>, Ritesh Harjain <ritesh.harjani@...il.com>, Russell King <linux@....linux.org.uk>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCHv6 3/5] common: dma-mapping: Introduce common remapping functions On 8/8/2014 3:45 PM, Andrew Morton wrote: > On Fri, 8 Aug 2014 13:23:15 -0700 Laura Abbott <lauraa@...eaurora.org> wrote: > >> >> For architectures without coherent DMA, memory for DMA may >> need to be remapped with coherent attributes. Factor out >> the the remapping code from arm and put it in a >> common location to reduce code duplication. >> >> As part of this, the arm APIs are now migrated away from >> ioremap_page_range to the common APIs which use map_vm_area for remapping. >> This should be an equivalent change and using map_vm_area is more >> correct as ioremap_page_range is intended to bring in io addresses >> into the cpu space and not regular kernel managed memory. >> >> ... >> >> @@ -267,3 +269,68 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, >> return ret; >> } >> EXPORT_SYMBOL(dma_common_mmap); >> + >> +/* >> + * remaps an allocated contiguous region into another vm_area. >> + * Cannot be used in non-sleeping contexts >> + */ >> + >> +void *dma_common_contiguous_remap(struct page *page, size_t size, >> + unsigned long vm_flags, >> + pgprot_t prot, const void *caller) >> +{ >> + int i; >> + struct page **pages; >> + void *ptr; >> + >> + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL); >> + if (!pages) >> + return NULL; >> + >> + for (i = 0; i < (size >> PAGE_SHIFT); i++) >> + pages[i] = page + i; > > Assumes a single mem_map[] array. That's not the case for sparsemem > (at least). > > Good point. I guess the best option is to increment via pfn and call pfn_to_page. Either that or go back to slightly abusing ioremap_page_range to remap normal memory. Thanks, Laura -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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