From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v2 5/5] ARM: Unconditionally enable ARM_DMA_USE_IOMMU Date: Wed, 25 Apr 2018 08:17:45 -0700 Message-ID: <20180425151745.GA16075@infradead.org> References: <20180425101051.15349-1-thierry.reding@gmail.com> <20180425101051.15349-5-thierry.reding@gmail.com> <20180425102511.GP16141@n2100.armlinux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180425102511.GP16141@n2100.armlinux.org.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Russell King - ARM Linux Cc: nouveau@lists.freedesktop.org, Joerg Roedel , dri-devel@lists.freedesktop.org, Christoph Hellwig , iommu@lists.linux-foundation.org, Thierry Reding , Daniel Vetter , linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-tegra@vger.kernel.org On Wed, Apr 25, 2018 at 11:25:11AM +0100, Russell King - ARM Linux wrote: > > config ARM_DMA_USE_IOMMU > > - bool > > + def_bool y > > select ARM_HAS_SG_CHAIN > > select NEED_SG_DMA_LENGTH > > This doesn't work - as has recently been discussed with hch, we can't > globally enable NEED_SG_DMA_LENGTH on ARM - the ARM architecture > pre-dates the addition of the DMA length member in the scatterlist, > and not every machine supports the splitting of the DMA length from > the non-DMA length member. Hence, this will cause a regression, > sorry. Agreed as-is. However supporting it everywhere should not be much work, I'll take a look at it.