From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 3716E6B004A for ; Mon, 13 Jun 2011 11:40:19 -0400 (EDT) Received: by wyf19 with SMTP id 19so4365704wyf.14 for ; Mon, 13 Jun 2011 08:40:15 -0700 (PDT) Date: Mon, 13 Jun 2011 16:40:33 +0100 From: Catalin Marinas Subject: Re: [RFC 0/2] ARM: DMA-mapping & IOMMU integration Message-ID: <20110613154033.GA29185@1n450.cable.virginmedia.net> References: <1306308920-8602-1-git-send-email-m.szyprowski@samsung.com> <201106131707.49217.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: KyongHo Cho Cc: Arnd Bergmann , Russell King - ARM Linux , Joerg Roedel , linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, Kyungmin Park , linux-arm-kernel@lists.infradead.org, Marek Szyprowski On Tue, Jun 14, 2011 at 12:30:44AM +0900, KyongHo Cho wrote: > On Tue, Jun 14, 2011 at 12:07 AM, Arnd Bergmann wrote: > > I'm sure that the graphics people will disagree with you on that. > > Having the frame buffer mapped in write-combine mode is rather > > important when you want to efficiently output videos from your > > CPU. > > I agree with you. > But I am discussing about dma_alloc_writecombine() in ARM. > You can see that only ARM and AVR32 implement it and there are few > drivers which use it. > No function in dma_map_ops corresponds to dma_alloc_writecombine(). > That's why Marek tried to add 'alloc_writecombine' to dma_map_ops. FWIW, on ARMv6 and later hardware, the dma_alloc_coherent() provides writecombine memory (i.e. Normal Noncacheable), so no need for dma_alloc_writecombine(). On earlier architectures it is creating Strongly Ordered mappings (no writecombine). -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org