From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id ACF396B0087 for ; Thu, 23 Dec 2010 07:20:36 -0500 (EST) Date: Thu, 23 Dec 2010 12:19:18 +0000 From: Russell King - ARM Linux Subject: Re: [PATCHv8 00/12] Contiguous Memory Allocator Message-ID: <20101223121917.GG3636@n2100.arm.linux.org.uk> References: <20101223100642.GD3636@n2100.arm.linux.org.uk> <00ea01cba290$4d67f500$e837df00$%szyprowski@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <00ea01cba290$4d67f500$e837df00$%szyprowski@samsung.com> Sender: owner-linux-mm@kvack.org To: Marek Szyprowski Cc: 'Kyungmin Park' , 'Michal Nazarewicz' , linux-arm-kernel@lists.infradead.org, 'Daniel Walker' , 'Johan MOSSBERG' , 'Mel Gorman' , linux-kernel@vger.kernel.org, 'Michal Nazarewicz' , linux-mm@kvack.org, 'Ankita Garg' , 'Andrew Morton' , linux-media@vger.kernel.org, 'KAMEZAWA Hiroyuki' List-ID: On Thu, Dec 23, 2010 at 11:58:08AM +0100, Marek Szyprowski wrote: > Actually this contiguous memory allocator is a better replacement for > alloc_pages() which is used by dma_alloc_coherent(). It is a generic > framework that is not tied only to ARM architecture. ... which is open to abuse. What I'm trying to find out is - if it can't be used for DMA, what is it to be used for? Or are we inventing an everything-but-ARM framework? > > In other words, do we _actually_ have a use for this which doesn't > > involve doing something like allocating 32MB of memory from it, > > remapping it so that it's DMA coherent, and then performing DMA > > on the resulting buffer? > > This is an arm specific problem, also related to dma_alloc_coherent() > allocator. To be 100% conformant with ARM specification we would > probably need to unmap all pages used by the dma_coherent allocator > from the LOW MEM area. This is doable, but completely not related > to the CMA and this patch series. You've already been told why we can't unmap pages from the kernel direct mapping. Okay, so I'm just going to assume that CMA has _no_ _business_ being used on ARM, and is not something that should interest anyone in the ARM community. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org