From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by kanga.kvack.org (Postfix) with ESMTP id 632416B0035 for ; Mon, 11 Aug 2014 14:05:17 -0400 (EDT) Received: by mail-wi0-f176.google.com with SMTP id bs8so4676316wib.9 for ; Mon, 11 Aug 2014 11:05:16 -0700 (PDT) Received: from collaborate-mta1.arm.com (fw-tnat.austin.arm.com. [217.140.110.23]) by mx.google.com with ESMTP id l1si18958179wif.13.2014.08.11.11.05.14 for ; Mon, 11 Aug 2014 11:05:14 -0700 (PDT) Date: Mon, 11 Aug 2014 19:04:36 +0100 From: Catalin Marinas Subject: Re: [PATCHv6 3/5] common: dma-mapping: Introduce common remapping functions Message-ID: <20140811180436.GH13871@arm.com> References: <1407529397-6642-1-git-send-email-lauraa@codeaurora.org> <1407529397-6642-3-git-send-email-lauraa@codeaurora.org> <20140808154556.11c7bf68d1bcf2714c148e3b@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140808154556.11c7bf68d1bcf2714c148e3b@linux-foundation.org> Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Laura Abbott , Will Deacon , Russell King , David Riley , "linux-arm-kernel@lists.infradead.org" , Ritesh Harjain , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Thierry Reding , Arnd Bergmann On Fri, Aug 08, 2014 at 11:45:56PM +0100, Andrew Morton wrote: > On Fri, 8 Aug 2014 13:23:15 -0700 Laura Abbott 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. The "page" pointer (and memory range) passed to this function has been allocated with alloc_pages(), so the range is guaranteed to be physically contiguous but it does not imply a single mem_map[] array. For arm64 with SPARSEMEM_VMEMMAP_ENABLE it's safe but not all architectures use this (especially on 32-bit). What about using pfn_to_page(pfn + i)? Thanks. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org