From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f47.google.com (mail-wg0-f47.google.com [74.125.82.47]) by kanga.kvack.org (Postfix) with ESMTP id D95AF6B0037 for ; Mon, 11 Aug 2014 14:06:10 -0400 (EDT) Received: by mail-wg0-f47.google.com with SMTP id b13so8697250wgh.6 for ; Mon, 11 Aug 2014 11:06:10 -0700 (PDT) Received: from collaborate-mta1.arm.com (fw-tnat.austin.arm.com. [217.140.110.23]) by mx.google.com with ESMTP id v11si27382311wjr.176.2014.08.11.11.06.09 for ; Mon, 11 Aug 2014 11:06:09 -0700 (PDT) Date: Mon, 11 Aug 2014 19:05:42 +0100 From: Catalin Marinas Subject: Re: [PATCHv6 3/5] common: dma-mapping: Introduce common remapping functions Message-ID: <20140811180542.GI13871@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> <53E55C86.3040705@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53E55C86.3040705@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: Laura Abbott Cc: Andrew Morton , David Riley , Arnd Bergmann , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Thierry Reding , Ritesh Harjain , Russell King , "linux-arm-kernel@lists.infradead.org" On Sat, Aug 09, 2014 at 12:25:58AM +0100, Laura Abbott wrote: > On 8/8/2014 3:45 PM, 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. 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. I now noticed you suggested the pfn_to_page(). I think this should work and it's better than ioremap_page_range(). -- 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