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 SMTP id 862E76B0169 for ; Tue, 16 Aug 2011 06:18:08 -0400 (EDT) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii Received: from spt2.w1.samsung.com ([210.118.77.13]) by mailout3.w1.samsung.com (Sun Java(tm) System Messaging Server 6.3-8.04 (built Jul 29 2009; 32bit)) with ESMTP id <0LQ000GURNA46I00@mailout3.w1.samsung.com> for linux-mm@kvack.org; Tue, 16 Aug 2011 11:18:04 +0100 (BST) Received: from linux.samsung.com ([106.116.38.10]) by spt2.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTPA id <0LQ0000Z0NA3ZG@spt2.w1.samsung.com> for linux-mm@kvack.org; Tue, 16 Aug 2011 11:18:03 +0100 (BST) Date: Tue, 16 Aug 2011 12:17:30 +0200 From: Marek Szyprowski Subject: RE: [PATCH 7/9] ARM: DMA: steal memory for DMA coherent mappings In-reply-to: <201108121453.05898.arnd@arndb.de> Message-id: <004301cc5bfd$b50048d0$1f00da70$%szyprowski@samsung.com> Content-language: pl References: <1313146711-1767-1-git-send-email-m.szyprowski@samsung.com> <1313146711-1767-8-git-send-email-m.szyprowski@samsung.com> <201108121453.05898.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: 'Arnd Bergmann' Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, 'Michal Nazarewicz' , 'Kyungmin Park' , 'Russell King' , 'Andrew Morton' , 'KAMEZAWA Hiroyuki' , 'Ankita Garg' , 'Daniel Walker' , 'Mel Gorman' , 'Jesse Barker' , 'Jonathan Corbet' , 'Shariq Hasnain' , 'Chunsang Jeong' Hello, On Friday, August 12, 2011 2:53 PM Arnd Bergmann wrote: > On Friday 12 August 2011, Marek Szyprowski wrote: > > > > From: Russell King > > > > Steal memory from the kernel to provide coherent DMA memory to drivers. > > This avoids the problem with multiple mappings with differing attributes > > on later CPUs. > > > > Signed-off-by: Russell King > > [m.szyprowski: rebased onto 3.1-rc1] > > Signed-off-by: Marek Szyprowski > > Hi Marek, > > Is this the same patch that Russell had to revert because it didn't > work on some of the older machines, in particular those using > dmabounce? Yes. > I thought that our discussion ended with the plan to use this only > for ARMv6+ (which has a problem with double mapping) but not on ARMv5 > and below (which don't have this problem but might need dmabounce). Ok, my fault. I've forgot to mention that this patch was almost ready during Linaro meeting, but I didn't manage to post it that time. Of course it doesn't fulfill all the agreements from that discussion. I was only unsure if we should care about the case where CMA is not enabled for ARMv6+ or not. This patch was prepared in assumption that dma_alloc_coherent should work in both cases - with and without CMA. Now I assume that for ARMv6+ the CMA should be enabled unconditionally. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org